<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/drivers, branch v5.4.243</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>drm/amd/display: Fix hang when skipping modeset</title>
<updated>2023-05-17T09:36:05+00:00</updated>
<author>
<name>Aurabindo Pillai</name>
<email>aurabindo.pillai@amd.com</email>
</author>
<published>2023-03-24T14:42:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=d60f15682a5ce51e8119c1b9ff522494554e33b5'/>
<id>d60f15682a5ce51e8119c1b9ff522494554e33b5</id>
<content type='text'>
commit da5e14909776edea4462672fb4a3007802d262e7 upstream.

[Why&amp;How]

When skipping full modeset since the only state change was a front porch
change, the DC commit sequence requires extra checks to handle non
existant plane states being asked to be removed from context.

Reviewed-by: Alvin Lee &lt;Alvin.Lee2@amd.com&gt;
Acked-by: Qingqing Zhuo &lt;qingqing.zhuo@amd.com&gt;
Signed-off-by: Aurabindo Pillai &lt;aurabindo.pillai@amd.com&gt;
Tested-by: Daniel Wheeler &lt;daniel.wheeler@amd.com&gt;
Signed-off-by: Alex Deucher &lt;alexander.deucher@amd.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit da5e14909776edea4462672fb4a3007802d262e7 upstream.

[Why&amp;How]

When skipping full modeset since the only state change was a front porch
change, the DC commit sequence requires extra checks to handle non
existant plane states being asked to be removed from context.

Reviewed-by: Alvin Lee &lt;Alvin.Lee2@amd.com&gt;
Acked-by: Qingqing Zhuo &lt;qingqing.zhuo@amd.com&gt;
Signed-off-by: Aurabindo Pillai &lt;aurabindo.pillai@amd.com&gt;
Tested-by: Daniel Wheeler &lt;daniel.wheeler@amd.com&gt;
Signed-off-by: Alex Deucher &lt;alexander.deucher@amd.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>drm/exynos: move to use request_irq by IRQF_NO_AUTOEN flag</title>
<updated>2023-05-17T09:36:05+00:00</updated>
<author>
<name>Tian Tao</name>
<email>tiantao6@hisilicon.com</email>
</author>
<published>2021-03-15T11:49:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=3f231e30cdeb18d2af68af63e6650bb7f5652450'/>
<id>3f231e30cdeb18d2af68af63e6650bb7f5652450</id>
<content type='text'>
commit a4e5eed2c6a689ef2b6ad8d7ae86665c69039379 upstream.

After this patch cbe16f35bee68 genirq: Add IRQF_NO_AUTOEN for
request_irq/nmi() is merged. request_irq() after setting
IRQ_NOAUTOEN as below

irq_set_status_flags(irq, IRQ_NOAUTOEN);
request_irq(dev, irq...);
can be replaced by request_irq() with IRQF_NO_AUTOEN flag.

v2:
Fix the problem of using wrong flags

Signed-off-by: Tian Tao &lt;tiantao6@hisilicon.com&gt;
Signed-off-by: Inki Dae &lt;inki.dae@samsung.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit a4e5eed2c6a689ef2b6ad8d7ae86665c69039379 upstream.

After this patch cbe16f35bee68 genirq: Add IRQF_NO_AUTOEN for
request_irq/nmi() is merged. request_irq() after setting
IRQ_NOAUTOEN as below

irq_set_status_flags(irq, IRQ_NOAUTOEN);
request_irq(dev, irq...);
can be replaced by request_irq() with IRQF_NO_AUTOEN flag.

v2:
Fix the problem of using wrong flags

Signed-off-by: Tian Tao &lt;tiantao6@hisilicon.com&gt;
Signed-off-by: Inki Dae &lt;inki.dae@samsung.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>drm/msm/adreno: Fix null ptr access in adreno_gpu_cleanup()</title>
<updated>2023-05-17T09:36:05+00:00</updated>
<author>
<name>Akhil P Oommen</name>
<email>quic_akhilpo@quicinc.com</email>
</author>
<published>2022-12-21T15:09:56+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=65a8b6d129cfcf63a2b8a36a63d275479ba6a217'/>
<id>65a8b6d129cfcf63a2b8a36a63d275479ba6a217</id>
<content type='text'>
commit dbeedbcb268d055d8895aceca427f897e12c2b50 upstream.

Fix the below kernel panic due to null pointer access:
[   18.504431] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000048
[   18.513464] Mem abort info:
[   18.516346]   ESR = 0x0000000096000005
[   18.520204]   EC = 0x25: DABT (current EL), IL = 32 bits
[   18.525706]   SET = 0, FnV = 0
[   18.528878]   EA = 0, S1PTW = 0
[   18.532117]   FSC = 0x05: level 1 translation fault
[   18.537138] Data abort info:
[   18.540110]   ISV = 0, ISS = 0x00000005
[   18.544060]   CM = 0, WnR = 0
[   18.547109] user pgtable: 4k pages, 39-bit VAs, pgdp=0000000112826000
[   18.553738] [0000000000000048] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000
[   18.562690] Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
**Snip**
[   18.696758] Call trace:
[   18.699278]  adreno_gpu_cleanup+0x30/0x88
[   18.703396]  a6xx_destroy+0xc0/0x130
[   18.707066]  a6xx_gpu_init+0x308/0x424
[   18.710921]  adreno_bind+0x178/0x288
[   18.714590]  component_bind_all+0xe0/0x214
[   18.718797]  msm_drm_bind+0x1d4/0x614
[   18.722566]  try_to_bring_up_aggregate_device+0x16c/0x1b8
[   18.728105]  __component_add+0xa0/0x158
[   18.732048]  component_add+0x20/0x2c
[   18.735719]  adreno_probe+0x40/0xc0
[   18.739300]  platform_probe+0xb4/0xd4
[   18.743068]  really_probe+0xfc/0x284
[   18.746738]  __driver_probe_device+0xc0/0xec
[   18.751129]  driver_probe_device+0x48/0x110
[   18.755421]  __device_attach_driver+0xa8/0xd0
[   18.759900]  bus_for_each_drv+0x90/0xdc
[   18.763843]  __device_attach+0xfc/0x174
[   18.767786]  device_initial_probe+0x20/0x2c
[   18.772090]  bus_probe_device+0x40/0xa0
[   18.776032]  deferred_probe_work_func+0x94/0xd0
[   18.780686]  process_one_work+0x190/0x3d0
[   18.784805]  worker_thread+0x280/0x3d4
[   18.788659]  kthread+0x104/0x1c0
[   18.791981]  ret_from_fork+0x10/0x20
[   18.795654] Code: f9400408 aa0003f3 aa1f03f4 91142015 (f9402516)
[   18.801913] ---[ end trace 0000000000000000 ]---
[   18.809039] Kernel panic - not syncing: Oops: Fatal exception

Fixes: 17e822f7591f ("drm/msm: fix unbalanced pm_runtime_enable in adreno_gpu_{init, cleanup}")
Signed-off-by: Akhil P Oommen &lt;quic_akhilpo@quicinc.com&gt;
Patchwork: https://patchwork.freedesktop.org/patch/515605/
Link: https://lore.kernel.org/r/20221221203925.v2.1.Ib978de92c4bd000b515486aad72e96c2481f84d0@changeid
Signed-off-by: Rob Clark &lt;robdclark@chromium.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit dbeedbcb268d055d8895aceca427f897e12c2b50 upstream.

Fix the below kernel panic due to null pointer access:
[   18.504431] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000048
[   18.513464] Mem abort info:
[   18.516346]   ESR = 0x0000000096000005
[   18.520204]   EC = 0x25: DABT (current EL), IL = 32 bits
[   18.525706]   SET = 0, FnV = 0
[   18.528878]   EA = 0, S1PTW = 0
[   18.532117]   FSC = 0x05: level 1 translation fault
[   18.537138] Data abort info:
[   18.540110]   ISV = 0, ISS = 0x00000005
[   18.544060]   CM = 0, WnR = 0
[   18.547109] user pgtable: 4k pages, 39-bit VAs, pgdp=0000000112826000
[   18.553738] [0000000000000048] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000
[   18.562690] Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
**Snip**
[   18.696758] Call trace:
[   18.699278]  adreno_gpu_cleanup+0x30/0x88
[   18.703396]  a6xx_destroy+0xc0/0x130
[   18.707066]  a6xx_gpu_init+0x308/0x424
[   18.710921]  adreno_bind+0x178/0x288
[   18.714590]  component_bind_all+0xe0/0x214
[   18.718797]  msm_drm_bind+0x1d4/0x614
[   18.722566]  try_to_bring_up_aggregate_device+0x16c/0x1b8
[   18.728105]  __component_add+0xa0/0x158
[   18.732048]  component_add+0x20/0x2c
[   18.735719]  adreno_probe+0x40/0xc0
[   18.739300]  platform_probe+0xb4/0xd4
[   18.743068]  really_probe+0xfc/0x284
[   18.746738]  __driver_probe_device+0xc0/0xec
[   18.751129]  driver_probe_device+0x48/0x110
[   18.755421]  __device_attach_driver+0xa8/0xd0
[   18.759900]  bus_for_each_drv+0x90/0xdc
[   18.763843]  __device_attach+0xfc/0x174
[   18.767786]  device_initial_probe+0x20/0x2c
[   18.772090]  bus_probe_device+0x40/0xa0
[   18.776032]  deferred_probe_work_func+0x94/0xd0
[   18.780686]  process_one_work+0x190/0x3d0
[   18.784805]  worker_thread+0x280/0x3d4
[   18.788659]  kthread+0x104/0x1c0
[   18.791981]  ret_from_fork+0x10/0x20
[   18.795654] Code: f9400408 aa0003f3 aa1f03f4 91142015 (f9402516)
[   18.801913] ---[ end trace 0000000000000000 ]---
[   18.809039] Kernel panic - not syncing: Oops: Fatal exception

Fixes: 17e822f7591f ("drm/msm: fix unbalanced pm_runtime_enable in adreno_gpu_{init, cleanup}")
Signed-off-by: Akhil P Oommen &lt;quic_akhilpo@quicinc.com&gt;
Patchwork: https://patchwork.freedesktop.org/patch/515605/
Link: https://lore.kernel.org/r/20221221203925.v2.1.Ib978de92c4bd000b515486aad72e96c2481f84d0@changeid
Signed-off-by: Rob Clark &lt;robdclark@chromium.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>firmware: raspberrypi: fix possible memory leak in rpi_firmware_probe()</title>
<updated>2023-05-17T09:36:05+00:00</updated>
<author>
<name>Yang Yingliang</name>
<email>yangyingliang@huawei.com</email>
</author>
<published>2022-11-17T07:06:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=62ac943eb2a9d655e431b9bc98ff6d7bd51a0e49'/>
<id>62ac943eb2a9d655e431b9bc98ff6d7bd51a0e49</id>
<content type='text'>
commit 7b51161696e803fd5f9ad55b20a64c2df313f95c upstream.

In rpi_firmware_probe(), if mbox_request_channel() fails, the 'fw' will
not be freed through rpi_firmware_delete(), fix this leak by calling
kfree() in the error path.

Fixes: 1e7c57355a3b ("firmware: raspberrypi: Keep count of all consumers")
Signed-off-by: Yang Yingliang &lt;yangyingliang@huawei.com&gt;
Link: https://lore.kernel.org/r/20221117070636.3849773-1-yangyingliang@huawei.com
Acked-by: Joel Savitz &lt;jsavitz@redhat.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 7b51161696e803fd5f9ad55b20a64c2df313f95c upstream.

In rpi_firmware_probe(), if mbox_request_channel() fails, the 'fw' will
not be freed through rpi_firmware_delete(), fix this leak by calling
kfree() in the error path.

Fixes: 1e7c57355a3b ("firmware: raspberrypi: Keep count of all consumers")
Signed-off-by: Yang Yingliang &lt;yangyingliang@huawei.com&gt;
Link: https://lore.kernel.org/r/20221117070636.3849773-1-yangyingliang@huawei.com
Acked-by: Joel Savitz &lt;jsavitz@redhat.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>drm/msm: Fix double pm_runtime_disable() call</title>
<updated>2023-05-17T09:36:04+00:00</updated>
<author>
<name>Maximilian Luz</name>
<email>luzmaximilian@gmail.com</email>
</author>
<published>2022-06-06T21:13:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=a781ea3437a08474844239003b65d8cc6a21baa7'/>
<id>a781ea3437a08474844239003b65d8cc6a21baa7</id>
<content type='text'>
commit ce0db505bc0c51ef5e9ba446c660de7e26f78f29 upstream.

Following commit 17e822f7591f ("drm/msm: fix unbalanced
pm_runtime_enable in adreno_gpu_{init, cleanup}"), any call to
adreno_unbind() will disable runtime PM twice, as indicated by the call
trees below:

  adreno_unbind()
   -&gt; pm_runtime_force_suspend()
   -&gt; pm_runtime_disable()

  adreno_unbind()
   -&gt; gpu-&gt;funcs-&gt;destroy() [= aNxx_destroy()]
   -&gt; adreno_gpu_cleanup()
   -&gt; pm_runtime_disable()

Note that pm_runtime_force_suspend() is called right before
gpu-&gt;funcs-&gt;destroy() and both functions are called unconditionally.

With recent addition of the eDP AUX bus code, this problem manifests
itself when the eDP panel cannot be found yet and probing is deferred.
On the first probe attempt, we disable runtime PM twice as described
above. This then causes any later probe attempt to fail with

  [drm:adreno_load_gpu [msm]] *ERROR* Couldn't power up the GPU: -13

preventing the driver from loading.

As there seem to be scenarios where the aNxx_destroy() functions are not
called from adreno_unbind(), simply removing pm_runtime_disable() from
inside adreno_unbind() does not seem to be the proper fix. This is what
commit 17e822f7591f ("drm/msm: fix unbalanced pm_runtime_enable in
adreno_gpu_{init, cleanup}") intended to fix. Therefore, instead check
whether runtime PM is still enabled, and only disable it in that case.

Fixes: 17e822f7591f ("drm/msm: fix unbalanced pm_runtime_enable in adreno_gpu_{init, cleanup}")
Signed-off-by: Maximilian Luz &lt;luzmaximilian@gmail.com&gt;
Tested-by: Bjorn Andersson &lt;bjorn.andersson@linaro.org&gt;
Reviewed-by: Rob Clark &lt;robdclark@gmail.com&gt;
Link: https://lore.kernel.org/r/20220606211305.189585-1-luzmaximilian@gmail.com
Signed-off-by: Rob Clark &lt;robdclark@chromium.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit ce0db505bc0c51ef5e9ba446c660de7e26f78f29 upstream.

Following commit 17e822f7591f ("drm/msm: fix unbalanced
pm_runtime_enable in adreno_gpu_{init, cleanup}"), any call to
adreno_unbind() will disable runtime PM twice, as indicated by the call
trees below:

  adreno_unbind()
   -&gt; pm_runtime_force_suspend()
   -&gt; pm_runtime_disable()

  adreno_unbind()
   -&gt; gpu-&gt;funcs-&gt;destroy() [= aNxx_destroy()]
   -&gt; adreno_gpu_cleanup()
   -&gt; pm_runtime_disable()

Note that pm_runtime_force_suspend() is called right before
gpu-&gt;funcs-&gt;destroy() and both functions are called unconditionally.

With recent addition of the eDP AUX bus code, this problem manifests
itself when the eDP panel cannot be found yet and probing is deferred.
On the first probe attempt, we disable runtime PM twice as described
above. This then causes any later probe attempt to fail with

  [drm:adreno_load_gpu [msm]] *ERROR* Couldn't power up the GPU: -13

preventing the driver from loading.

As there seem to be scenarios where the aNxx_destroy() functions are not
called from adreno_unbind(), simply removing pm_runtime_disable() from
inside adreno_unbind() does not seem to be the proper fix. This is what
commit 17e822f7591f ("drm/msm: fix unbalanced pm_runtime_enable in
adreno_gpu_{init, cleanup}") intended to fix. Therefore, instead check
whether runtime PM is still enabled, and only disable it in that case.

Fixes: 17e822f7591f ("drm/msm: fix unbalanced pm_runtime_enable in adreno_gpu_{init, cleanup}")
Signed-off-by: Maximilian Luz &lt;luzmaximilian@gmail.com&gt;
Tested-by: Bjorn Andersson &lt;bjorn.andersson@linaro.org&gt;
Reviewed-by: Rob Clark &lt;robdclark@gmail.com&gt;
Link: https://lore.kernel.org/r/20220606211305.189585-1-luzmaximilian@gmail.com
Signed-off-by: Rob Clark &lt;robdclark@chromium.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>PCI: pciehp: Fix AB-BA deadlock between reset_lock and device_lock</title>
<updated>2023-05-17T09:36:04+00:00</updated>
<author>
<name>Lukas Wunner</name>
<email>lukas@wunner.de</email>
</author>
<published>2023-05-09T10:41:10+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=c2c3ffc7989617effd9e3dada296a60c80726839'/>
<id>c2c3ffc7989617effd9e3dada296a60c80726839</id>
<content type='text'>
commit f5eff5591b8f9c5effd25c92c758a127765f74c1 upstream.

In 2013, commits

  2e35afaefe64 ("PCI: pciehp: Add reset_slot() method")
  608c388122c7 ("PCI: Add slot reset option to pci_dev_reset()")

amended PCIe hotplug to mask Presence Detect Changed events during a
Secondary Bus Reset.  The reset thus no longer causes gratuitous slot
bringdown and bringup.

However the commits neglected to serialize reset with code paths reading
slot registers.  For instance, a slot bringup due to an earlier hotplug
event may see the Presence Detect State bit cleared during a concurrent
Secondary Bus Reset.

In 2018, commit

  5b3f7b7d062b ("PCI: pciehp: Avoid slot access during reset")

retrofitted the missing locking.  It introduced a reset_lock which
serializes a Secondary Bus Reset with other parts of pciehp.

Unfortunately the locking turns out to be overzealous:  reset_lock is
held for the entire enumeration and de-enumeration of hotplugged devices,
including driver binding and unbinding.

Driver binding and unbinding acquires device_lock while the reset_lock
of the ancestral hotplug port is held.  A concurrent Secondary Bus Reset
acquires the ancestral reset_lock while already holding the device_lock.
The asymmetric locking order in the two code paths can lead to AB-BA
deadlocks.

Michael Haeuptle reports such deadlocks on simultaneous hot-removal and
vfio release (the latter implies a Secondary Bus Reset):

  pciehp_ist()                                    # down_read(reset_lock)
    pciehp_handle_presence_or_link_change()
      pciehp_disable_slot()
        __pciehp_disable_slot()
          remove_board()
            pciehp_unconfigure_device()
              pci_stop_and_remove_bus_device()
                pci_stop_bus_device()
                  pci_stop_dev()
                    device_release_driver()
                      device_release_driver_internal()
                        __device_driver_lock()    # device_lock()

  SYS_munmap()
    vfio_device_fops_release()
      vfio_device_group_close()
        vfio_device_close()
          vfio_device_last_close()
            vfio_pci_core_close_device()
              vfio_pci_core_disable()             # device_lock()
                __pci_reset_function_locked()
                  pci_reset_bus_function()
                    pci_dev_reset_slot_function()
                      pci_reset_hotplug_slot()
                        pciehp_reset_slot()       # down_write(reset_lock)

Ian May reports the same deadlock on simultaneous hot-removal and an
AER-induced Secondary Bus Reset:

  aer_recover_work_func()
    pcie_do_recovery()
      aer_root_reset()
        pci_bus_error_reset()
          pci_slot_reset()
            pci_slot_lock()                       # device_lock()
            pci_reset_hotplug_slot()
              pciehp_reset_slot()                 # down_write(reset_lock)

Fix by releasing the reset_lock during driver binding and unbinding,
thereby splitting and shrinking the critical section.

Driver binding and unbinding is protected by the device_lock() and thus
serialized with a Secondary Bus Reset.  There's no need to additionally
protect it with the reset_lock.  However, pciehp does not bind and
unbind devices directly, but rather invokes PCI core functions which
also perform certain enumeration and de-enumeration steps.

The reset_lock's purpose is to protect slot registers, not enumeration
and de-enumeration of hotplugged devices.  That would arguably be the
job of the PCI core, not the PCIe hotplug driver.  After all, an
AER-induced Secondary Bus Reset may as well happen during boot-time
enumeration of the PCI hierarchy and there's no locking to prevent that
either.

Exempting *de-enumeration* from the reset_lock is relatively harmless:
A concurrent Secondary Bus Reset may foil config space accesses such as
PME interrupt disablement.  But if the device is physically gone, those
accesses are pointless anyway.  If the device is physically present and
only logically removed through an Attention Button press or the sysfs
"power" attribute, PME interrupts as well as DMA cannot come through
because pciehp_unconfigure_device() disables INTx and Bus Master bits.
That's still protected by the reset_lock in the present commit.

Exempting *enumeration* from the reset_lock also has limited impact:
The exempted call to pci_bus_add_device() may perform device accesses
through pcibios_bus_add_device() and pci_fixup_device() which are now
no longer protected from a concurrent Secondary Bus Reset.  Otherwise
there should be no impact.

In essence, the present commit seeks to fix the AB-BA deadlocks while
still retaining a best-effort reset protection for enumeration and
de-enumeration of hotplugged devices -- until a general solution is
implemented in the PCI core.

Link: https://lore.kernel.org/linux-pci/CS1PR8401MB0728FC6FDAB8A35C22BD90EC95F10@CS1PR8401MB0728.NAMPRD84.PROD.OUTLOOK.COM
Link: https://lore.kernel.org/linux-pci/20200615143250.438252-1-ian.may@canonical.com
Link: https://lore.kernel.org/linux-pci/ce878dab-c0c4-5bd0-a725-9805a075682d@amd.com
Link: https://lore.kernel.org/linux-pci/ed831249-384a-6d35-0831-70af191e9bce@huawei.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215590
Fixes: 5b3f7b7d062b ("PCI: pciehp: Avoid slot access during reset")
Link: https://lore.kernel.org/r/fef2b2e9edf245c049a8c5b94743c0f74ff5008a.1681191902.git.lukas@wunner.de
Reported-by: Michael Haeuptle &lt;michael.haeuptle@hpe.com&gt;
Reported-by: Ian May &lt;ian.may@canonical.com&gt;
Reported-by: Andrey Grodzovsky &lt;andrey2805@gmail.com&gt;
Reported-by: Rahul Kumar &lt;rahul.kumar1@amd.com&gt;
Reported-by: Jialin Zhang &lt;zhangjialin11@huawei.com&gt;
Tested-by: Anatoli Antonovitch &lt;Anatoli.Antonovitch@amd.com&gt;
Signed-off-by: Lukas Wunner &lt;lukas@wunner.de&gt;
Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Cc: stable@vger.kernel.org # v4.19+
Cc: Dan Stein &lt;dstein@hpe.com&gt;
Cc: Ashok Raj &lt;ashok.raj@intel.com&gt;
Cc: Alex Michon &lt;amichon@kalrayinc.com&gt;
Cc: Xiongfeng Wang &lt;wangxiongfeng2@huawei.com&gt;
Cc: Alex Williamson &lt;alex.williamson@redhat.com&gt;
Cc: Mika Westerberg &lt;mika.westerberg@linux.intel.com&gt;
Cc: Sathyanarayanan Kuppuswamy &lt;sathyanarayanan.kuppuswamy@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit f5eff5591b8f9c5effd25c92c758a127765f74c1 upstream.

In 2013, commits

  2e35afaefe64 ("PCI: pciehp: Add reset_slot() method")
  608c388122c7 ("PCI: Add slot reset option to pci_dev_reset()")

amended PCIe hotplug to mask Presence Detect Changed events during a
Secondary Bus Reset.  The reset thus no longer causes gratuitous slot
bringdown and bringup.

However the commits neglected to serialize reset with code paths reading
slot registers.  For instance, a slot bringup due to an earlier hotplug
event may see the Presence Detect State bit cleared during a concurrent
Secondary Bus Reset.

In 2018, commit

  5b3f7b7d062b ("PCI: pciehp: Avoid slot access during reset")

retrofitted the missing locking.  It introduced a reset_lock which
serializes a Secondary Bus Reset with other parts of pciehp.

Unfortunately the locking turns out to be overzealous:  reset_lock is
held for the entire enumeration and de-enumeration of hotplugged devices,
including driver binding and unbinding.

Driver binding and unbinding acquires device_lock while the reset_lock
of the ancestral hotplug port is held.  A concurrent Secondary Bus Reset
acquires the ancestral reset_lock while already holding the device_lock.
The asymmetric locking order in the two code paths can lead to AB-BA
deadlocks.

Michael Haeuptle reports such deadlocks on simultaneous hot-removal and
vfio release (the latter implies a Secondary Bus Reset):

  pciehp_ist()                                    # down_read(reset_lock)
    pciehp_handle_presence_or_link_change()
      pciehp_disable_slot()
        __pciehp_disable_slot()
          remove_board()
            pciehp_unconfigure_device()
              pci_stop_and_remove_bus_device()
                pci_stop_bus_device()
                  pci_stop_dev()
                    device_release_driver()
                      device_release_driver_internal()
                        __device_driver_lock()    # device_lock()

  SYS_munmap()
    vfio_device_fops_release()
      vfio_device_group_close()
        vfio_device_close()
          vfio_device_last_close()
            vfio_pci_core_close_device()
              vfio_pci_core_disable()             # device_lock()
                __pci_reset_function_locked()
                  pci_reset_bus_function()
                    pci_dev_reset_slot_function()
                      pci_reset_hotplug_slot()
                        pciehp_reset_slot()       # down_write(reset_lock)

Ian May reports the same deadlock on simultaneous hot-removal and an
AER-induced Secondary Bus Reset:

  aer_recover_work_func()
    pcie_do_recovery()
      aer_root_reset()
        pci_bus_error_reset()
          pci_slot_reset()
            pci_slot_lock()                       # device_lock()
            pci_reset_hotplug_slot()
              pciehp_reset_slot()                 # down_write(reset_lock)

Fix by releasing the reset_lock during driver binding and unbinding,
thereby splitting and shrinking the critical section.

Driver binding and unbinding is protected by the device_lock() and thus
serialized with a Secondary Bus Reset.  There's no need to additionally
protect it with the reset_lock.  However, pciehp does not bind and
unbind devices directly, but rather invokes PCI core functions which
also perform certain enumeration and de-enumeration steps.

The reset_lock's purpose is to protect slot registers, not enumeration
and de-enumeration of hotplugged devices.  That would arguably be the
job of the PCI core, not the PCIe hotplug driver.  After all, an
AER-induced Secondary Bus Reset may as well happen during boot-time
enumeration of the PCI hierarchy and there's no locking to prevent that
either.

Exempting *de-enumeration* from the reset_lock is relatively harmless:
A concurrent Secondary Bus Reset may foil config space accesses such as
PME interrupt disablement.  But if the device is physically gone, those
accesses are pointless anyway.  If the device is physically present and
only logically removed through an Attention Button press or the sysfs
"power" attribute, PME interrupts as well as DMA cannot come through
because pciehp_unconfigure_device() disables INTx and Bus Master bits.
That's still protected by the reset_lock in the present commit.

Exempting *enumeration* from the reset_lock also has limited impact:
The exempted call to pci_bus_add_device() may perform device accesses
through pcibios_bus_add_device() and pci_fixup_device() which are now
no longer protected from a concurrent Secondary Bus Reset.  Otherwise
there should be no impact.

In essence, the present commit seeks to fix the AB-BA deadlocks while
still retaining a best-effort reset protection for enumeration and
de-enumeration of hotplugged devices -- until a general solution is
implemented in the PCI core.

Link: https://lore.kernel.org/linux-pci/CS1PR8401MB0728FC6FDAB8A35C22BD90EC95F10@CS1PR8401MB0728.NAMPRD84.PROD.OUTLOOK.COM
Link: https://lore.kernel.org/linux-pci/20200615143250.438252-1-ian.may@canonical.com
Link: https://lore.kernel.org/linux-pci/ce878dab-c0c4-5bd0-a725-9805a075682d@amd.com
Link: https://lore.kernel.org/linux-pci/ed831249-384a-6d35-0831-70af191e9bce@huawei.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215590
Fixes: 5b3f7b7d062b ("PCI: pciehp: Avoid slot access during reset")
Link: https://lore.kernel.org/r/fef2b2e9edf245c049a8c5b94743c0f74ff5008a.1681191902.git.lukas@wunner.de
Reported-by: Michael Haeuptle &lt;michael.haeuptle@hpe.com&gt;
Reported-by: Ian May &lt;ian.may@canonical.com&gt;
Reported-by: Andrey Grodzovsky &lt;andrey2805@gmail.com&gt;
Reported-by: Rahul Kumar &lt;rahul.kumar1@amd.com&gt;
Reported-by: Jialin Zhang &lt;zhangjialin11@huawei.com&gt;
Tested-by: Anatoli Antonovitch &lt;Anatoli.Antonovitch@amd.com&gt;
Signed-off-by: Lukas Wunner &lt;lukas@wunner.de&gt;
Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Cc: stable@vger.kernel.org # v4.19+
Cc: Dan Stein &lt;dstein@hpe.com&gt;
Cc: Ashok Raj &lt;ashok.raj@intel.com&gt;
Cc: Alex Michon &lt;amichon@kalrayinc.com&gt;
Cc: Xiongfeng Wang &lt;wangxiongfeng2@huawei.com&gt;
Cc: Alex Williamson &lt;alex.williamson@redhat.com&gt;
Cc: Mika Westerberg &lt;mika.westerberg@linux.intel.com&gt;
Cc: Sathyanarayanan Kuppuswamy &lt;sathyanarayanan.kuppuswamy@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>PCI: pciehp: Use down_read/write_nested(reset_lock) to fix lockdep errors</title>
<updated>2023-05-17T09:36:04+00:00</updated>
<author>
<name>Hans de Goede</name>
<email>hdegoede@redhat.com</email>
</author>
<published>2023-05-09T10:41:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=6a24285f64ea2f668a86752b4a6f46eafebd18c2'/>
<id>6a24285f64ea2f668a86752b4a6f46eafebd18c2</id>
<content type='text'>
commit 085a9f43433f30cbe8a1ade62d9d7827c3217f4d upstream.

Use down_read_nested() and down_write_nested() when taking the
ctrl-&gt;reset_lock rw-sem, passing the number of PCIe hotplug controllers in
the path to the PCI root bus as lock subclass parameter.

This fixes the following false-positive lockdep report when unplugging a
Lenovo X1C8 from a Lenovo 2nd gen TB3 dock:

  pcieport 0000:06:01.0: pciehp: Slot(1): Link Down
  pcieport 0000:06:01.0: pciehp: Slot(1): Card not present
  ============================================
  WARNING: possible recursive locking detected
  5.16.0-rc2+ #621 Not tainted
  --------------------------------------------
  irq/124-pciehp/86 is trying to acquire lock:
  ffff8e5ac4299ef8 (&amp;ctrl-&gt;reset_lock){.+.+}-{3:3}, at: pciehp_check_presence+0x23/0x80

  but task is already holding lock:
  ffff8e5ac4298af8 (&amp;ctrl-&gt;reset_lock){.+.+}-{3:3}, at: pciehp_ist+0xf3/0x180

   other info that might help us debug this:
   Possible unsafe locking scenario:

	 CPU0
	 ----
    lock(&amp;ctrl-&gt;reset_lock);
    lock(&amp;ctrl-&gt;reset_lock);

   *** DEADLOCK ***

   May be due to missing lock nesting notation

  3 locks held by irq/124-pciehp/86:
   #0: ffff8e5ac4298af8 (&amp;ctrl-&gt;reset_lock){.+.+}-{3:3}, at: pciehp_ist+0xf3/0x180
   #1: ffffffffa3b024e8 (pci_rescan_remove_lock){+.+.}-{3:3}, at: pciehp_unconfigure_device+0x31/0x110
   #2: ffff8e5ac1ee2248 (&amp;dev-&gt;mutex){....}-{3:3}, at: device_release_driver+0x1c/0x40

  stack backtrace:
  CPU: 4 PID: 86 Comm: irq/124-pciehp Not tainted 5.16.0-rc2+ #621
  Hardware name: LENOVO 20U90SIT19/20U90SIT19, BIOS N2WET30W (1.20 ) 08/26/2021
  Call Trace:
   &lt;TASK&gt;
   dump_stack_lvl+0x59/0x73
   __lock_acquire.cold+0xc5/0x2c6
   lock_acquire+0xb5/0x2b0
   down_read+0x3e/0x50
   pciehp_check_presence+0x23/0x80
   pciehp_runtime_resume+0x5c/0xa0
   device_for_each_child+0x45/0x70
   pcie_port_device_runtime_resume+0x20/0x30
   pci_pm_runtime_resume+0xa7/0xc0
   __rpm_callback+0x41/0x110
   rpm_callback+0x59/0x70
   rpm_resume+0x512/0x7b0
   __pm_runtime_resume+0x4a/0x90
   __device_release_driver+0x28/0x240
   device_release_driver+0x26/0x40
   pci_stop_bus_device+0x68/0x90
   pci_stop_bus_device+0x2c/0x90
   pci_stop_and_remove_bus_device+0xe/0x20
   pciehp_unconfigure_device+0x6c/0x110
   pciehp_disable_slot+0x5b/0xe0
   pciehp_handle_presence_or_link_change+0xc3/0x2f0
   pciehp_ist+0x179/0x180

This lockdep warning is triggered because with Thunderbolt, hotplug ports
are nested. When removing multiple devices in a daisy-chain, each hotplug
port's reset_lock may be acquired recursively. It's never the same lock, so
the lockdep splat is a false positive.

Because locks at the same hierarchy level are never acquired recursively, a
per-level lockdep class is sufficient to fix the lockdep warning.

The choice to use one lockdep subclass per pcie-hotplug controller in the
path to the root-bus was made to conserve class keys because their number
is limited and the complexity grows quadratically with number of keys
according to Documentation/locking/lockdep-design.rst.

Link: https://lore.kernel.org/linux-pci/20190402021933.GA2966@mit.edu/
Link: https://lore.kernel.org/linux-pci/de684a28-9038-8fc6-27ca-3f6f2f6400d7@redhat.com/
Link: https://lore.kernel.org/r/20211217141709.379663-1-hdegoede@redhat.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=208855
Reported-by: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Signed-off-by: Hans de Goede &lt;hdegoede@redhat.com&gt;
Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Reviewed-by: Lukas Wunner &lt;lukas@wunner.de&gt;
Cc: stable@vger.kernel.org
[lukas: backport to v5.4-stable]
Signed-off-by: Lukas Wunner &lt;lukas@wunner.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 085a9f43433f30cbe8a1ade62d9d7827c3217f4d upstream.

Use down_read_nested() and down_write_nested() when taking the
ctrl-&gt;reset_lock rw-sem, passing the number of PCIe hotplug controllers in
the path to the PCI root bus as lock subclass parameter.

This fixes the following false-positive lockdep report when unplugging a
Lenovo X1C8 from a Lenovo 2nd gen TB3 dock:

  pcieport 0000:06:01.0: pciehp: Slot(1): Link Down
  pcieport 0000:06:01.0: pciehp: Slot(1): Card not present
  ============================================
  WARNING: possible recursive locking detected
  5.16.0-rc2+ #621 Not tainted
  --------------------------------------------
  irq/124-pciehp/86 is trying to acquire lock:
  ffff8e5ac4299ef8 (&amp;ctrl-&gt;reset_lock){.+.+}-{3:3}, at: pciehp_check_presence+0x23/0x80

  but task is already holding lock:
  ffff8e5ac4298af8 (&amp;ctrl-&gt;reset_lock){.+.+}-{3:3}, at: pciehp_ist+0xf3/0x180

   other info that might help us debug this:
   Possible unsafe locking scenario:

	 CPU0
	 ----
    lock(&amp;ctrl-&gt;reset_lock);
    lock(&amp;ctrl-&gt;reset_lock);

   *** DEADLOCK ***

   May be due to missing lock nesting notation

  3 locks held by irq/124-pciehp/86:
   #0: ffff8e5ac4298af8 (&amp;ctrl-&gt;reset_lock){.+.+}-{3:3}, at: pciehp_ist+0xf3/0x180
   #1: ffffffffa3b024e8 (pci_rescan_remove_lock){+.+.}-{3:3}, at: pciehp_unconfigure_device+0x31/0x110
   #2: ffff8e5ac1ee2248 (&amp;dev-&gt;mutex){....}-{3:3}, at: device_release_driver+0x1c/0x40

  stack backtrace:
  CPU: 4 PID: 86 Comm: irq/124-pciehp Not tainted 5.16.0-rc2+ #621
  Hardware name: LENOVO 20U90SIT19/20U90SIT19, BIOS N2WET30W (1.20 ) 08/26/2021
  Call Trace:
   &lt;TASK&gt;
   dump_stack_lvl+0x59/0x73
   __lock_acquire.cold+0xc5/0x2c6
   lock_acquire+0xb5/0x2b0
   down_read+0x3e/0x50
   pciehp_check_presence+0x23/0x80
   pciehp_runtime_resume+0x5c/0xa0
   device_for_each_child+0x45/0x70
   pcie_port_device_runtime_resume+0x20/0x30
   pci_pm_runtime_resume+0xa7/0xc0
   __rpm_callback+0x41/0x110
   rpm_callback+0x59/0x70
   rpm_resume+0x512/0x7b0
   __pm_runtime_resume+0x4a/0x90
   __device_release_driver+0x28/0x240
   device_release_driver+0x26/0x40
   pci_stop_bus_device+0x68/0x90
   pci_stop_bus_device+0x2c/0x90
   pci_stop_and_remove_bus_device+0xe/0x20
   pciehp_unconfigure_device+0x6c/0x110
   pciehp_disable_slot+0x5b/0xe0
   pciehp_handle_presence_or_link_change+0xc3/0x2f0
   pciehp_ist+0x179/0x180

This lockdep warning is triggered because with Thunderbolt, hotplug ports
are nested. When removing multiple devices in a daisy-chain, each hotplug
port's reset_lock may be acquired recursively. It's never the same lock, so
the lockdep splat is a false positive.

Because locks at the same hierarchy level are never acquired recursively, a
per-level lockdep class is sufficient to fix the lockdep warning.

The choice to use one lockdep subclass per pcie-hotplug controller in the
path to the root-bus was made to conserve class keys because their number
is limited and the complexity grows quadratically with number of keys
according to Documentation/locking/lockdep-design.rst.

Link: https://lore.kernel.org/linux-pci/20190402021933.GA2966@mit.edu/
Link: https://lore.kernel.org/linux-pci/de684a28-9038-8fc6-27ca-3f6f2f6400d7@redhat.com/
Link: https://lore.kernel.org/r/20211217141709.379663-1-hdegoede@redhat.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=208855
Reported-by: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Signed-off-by: Hans de Goede &lt;hdegoede@redhat.com&gt;
Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Reviewed-by: Lukas Wunner &lt;lukas@wunner.de&gt;
Cc: stable@vger.kernel.org
[lukas: backport to v5.4-stable]
Signed-off-by: Lukas Wunner &lt;lukas@wunner.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>drbd: correctly submit flush bio on barrier</title>
<updated>2023-05-17T09:36:04+00:00</updated>
<author>
<name>Christoph Böhmwalder</name>
<email>christoph.boehmwalder@linbit.com</email>
</author>
<published>2023-05-03T12:19:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=dde34ef0bc7378ba58fb9e135d2583d2b280dc06'/>
<id>dde34ef0bc7378ba58fb9e135d2583d2b280dc06</id>
<content type='text'>
commit 3899d94e3831ee07ea6821c032dc297aec80586a upstream.

When we receive a flush command (or "barrier" in DRBD), we currently use
a REQ_OP_FLUSH with the REQ_PREFLUSH flag set.

The correct way to submit a flush bio is by using a REQ_OP_WRITE without
any data, and set the REQ_PREFLUSH flag.

Since commit b4a6bb3a67aa ("block: add a sanity check for non-write
flush/fua bios"), this triggers a warning in the block layer, but this
has been broken for quite some time before that.

So use the correct set of flags to actually make the flush happen.

Cc: Christoph Hellwig &lt;hch@infradead.org&gt;
Cc: stable@vger.kernel.org
Fixes: f9ff0da56437 ("drbd: allow parallel flushes for multi-volume resources")
Reported-by: Thomas Voegtle &lt;tv@lio96.de&gt;
Signed-off-by: Christoph Böhmwalder &lt;christoph.boehmwalder@linbit.com&gt;
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Link: https://lore.kernel.org/r/20230503121937.17232-1-christoph.boehmwalder@linbit.com
Signed-off-by: Jens Axboe &lt;axboe@kernel.dk&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 3899d94e3831ee07ea6821c032dc297aec80586a upstream.

When we receive a flush command (or "barrier" in DRBD), we currently use
a REQ_OP_FLUSH with the REQ_PREFLUSH flag set.

The correct way to submit a flush bio is by using a REQ_OP_WRITE without
any data, and set the REQ_PREFLUSH flag.

Since commit b4a6bb3a67aa ("block: add a sanity check for non-write
flush/fua bios"), this triggers a warning in the block layer, but this
has been broken for quite some time before that.

So use the correct set of flags to actually make the flush happen.

Cc: Christoph Hellwig &lt;hch@infradead.org&gt;
Cc: stable@vger.kernel.org
Fixes: f9ff0da56437 ("drbd: allow parallel flushes for multi-volume resources")
Reported-by: Thomas Voegtle &lt;tv@lio96.de&gt;
Signed-off-by: Christoph Böhmwalder &lt;christoph.boehmwalder@linbit.com&gt;
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Link: https://lore.kernel.org/r/20230503121937.17232-1-christoph.boehmwalder@linbit.com
Signed-off-by: Jens Axboe &lt;axboe@kernel.dk&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>serial: 8250: Fix serial8250_tx_empty() race with DMA Tx</title>
<updated>2023-05-17T09:36:04+00:00</updated>
<author>
<name>Ilpo Järvinen</name>
<email>ilpo.jarvinen@linux.intel.com</email>
</author>
<published>2023-05-11T12:32:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=373720b9289cffd62acd1247a54709c97073a0e3'/>
<id>373720b9289cffd62acd1247a54709c97073a0e3</id>
<content type='text'>
There's a potential race before THRE/TEMT deasserts when DMA Tx is
starting up (or the next batch of continuous Tx is being submitted).
This can lead to misdetecting Tx empty condition.

It is entirely normal for THRE/TEMT to be set for some time after the
DMA Tx had been setup in serial8250_tx_dma(). As Tx side is definitely
not empty at that point, it seems incorrect for serial8250_tx_empty()
claim Tx is empty.

Fix the race by also checking in serial8250_tx_empty() whether there's
DMA Tx active.

Note: This fix only addresses in-kernel race mainly to make using
TCSADRAIN/FLUSH robust. Userspace can still cause other races but they
seem userspace concurrency control problems.

Fixes: 9ee4b83e51f74 ("serial: 8250: Add support for dmaengine")
Cc: stable@vger.kernel.org
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Link: https://lore.kernel.org/r/20230317113318.31327-3-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
(cherry picked from commit 146a37e05d620cef4ad430e5d1c9c077fe6fa76f)
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
There's a potential race before THRE/TEMT deasserts when DMA Tx is
starting up (or the next batch of continuous Tx is being submitted).
This can lead to misdetecting Tx empty condition.

It is entirely normal for THRE/TEMT to be set for some time after the
DMA Tx had been setup in serial8250_tx_dma(). As Tx side is definitely
not empty at that point, it seems incorrect for serial8250_tx_empty()
claim Tx is empty.

Fix the race by also checking in serial8250_tx_empty() whether there's
DMA Tx active.

Note: This fix only addresses in-kernel race mainly to make using
TCSADRAIN/FLUSH robust. Userspace can still cause other races but they
seem userspace concurrency control problems.

Fixes: 9ee4b83e51f74 ("serial: 8250: Add support for dmaengine")
Cc: stable@vger.kernel.org
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Link: https://lore.kernel.org/r/20230317113318.31327-3-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
(cherry picked from commit 146a37e05d620cef4ad430e5d1c9c077fe6fa76f)
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>tty: Prevent writing chars during tcsetattr TCSADRAIN/FLUSH</title>
<updated>2023-05-17T09:36:04+00:00</updated>
<author>
<name>Ilpo Järvinen</name>
<email>ilpo.jarvinen@linux.intel.com</email>
</author>
<published>2023-05-11T12:32:43+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=f2a1071100feed7c20a6ae78269b536eb2a3867a'/>
<id>f2a1071100feed7c20a6ae78269b536eb2a3867a</id>
<content type='text'>
If userspace races tcsetattr() with a write, the drained condition
might not be guaranteed by the kernel. There is a race window after
checking Tx is empty before tty_set_termios() takes termios_rwsem for
write. During that race window, more characters can be queued by a
racing writer.

Any ongoing transmission might produce garbage during HW's
-&gt;set_termios() call. The intent of TCSADRAIN/FLUSH seems to be
preventing such a character corruption. If those flags are set, take
tty's write lock to stop any writer before performing the lower layer
Tx empty check and wait for the pending characters to be sent (if any).

The initial wait for all-writers-done must be placed outside of tty's
write lock to avoid deadlock which makes it impossible to use
tty_wait_until_sent(). The write lock is retried if a racing write is
detected.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Link: https://lore.kernel.org/r/20230317113318.31327-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
(cherry picked from commit 094fb49a2d0d6827c86d2e0840873e6db0c491d2)
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
If userspace races tcsetattr() with a write, the drained condition
might not be guaranteed by the kernel. There is a race window after
checking Tx is empty before tty_set_termios() takes termios_rwsem for
write. During that race window, more characters can be queued by a
racing writer.

Any ongoing transmission might produce garbage during HW's
-&gt;set_termios() call. The intent of TCSADRAIN/FLUSH seems to be
preventing such a character corruption. If those flags are set, take
tty's write lock to stop any writer before performing the lower layer
Tx empty check and wait for the pending characters to be sent (if any).

The initial wait for all-writers-done must be placed outside of tty's
write lock to avoid deadlock which makes it impossible to use
tty_wait_until_sent(). The write lock is retried if a racing write is
detected.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Link: https://lore.kernel.org/r/20230317113318.31327-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
(cherry picked from commit 094fb49a2d0d6827c86d2e0840873e6db0c491d2)
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
</feed>
