linux-stable.git/arch/um, branch v5.4.136

um: fix error return code in winch_tramp()

2021-07-20T14:10:49+00:00

[ Upstream commit ccf1236ecac476d9d2704866d9a476c86e387971 ]

Fix to return a negative error code from the error handling case instead
of 0, as done elsewhere in this function.

Fixes: 89df6bfc0405 ("uml: DEBUG_SHIRQ fixes")
Reported-by: Hulk Robot 
Signed-off-by: Zhen Lei 
Acked-By: anton.ivanov@cambridgegreys.com
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: fix error return code in slip_open()

2021-07-20T14:10:49+00:00

[ Upstream commit b77e81fbe5f5fb4ad9a61ec80f6d1e30b6da093a ]

Fix to return a negative error code from the error handling case instead
of 0, as done elsewhere in this function.

Fixes: a3c77c67a443 ("[PATCH] uml: slirp and slip driver cleanups and fixes")
Reported-by: Hulk Robot 
Signed-off-by: Zhen Lei 
Acked-By: anton.ivanov@cambridgegreys.com
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: Disable CONFIG_GCOV with MODULES

2021-05-22T09:38:28+00:00

[ Upstream commit ad3d19911632debc886ef4a992d41d6de7927006 ]

CONFIG_GCOV doesn't work with modules, and for various reasons
it cannot work, see also
https://lore.kernel.org/r/d36ea54d8c0a8dd706826ba844a6f27691f45d55.camel@sipsolutions.net

Make CONFIG_GCOV depend on !MODULES to avoid anyone
running into issues there. This also means we need
not export the gcov symbols.

Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: Mark all kernel symbols as local

2021-05-22T09:38:28+00:00

[ Upstream commit d5027ca63e0e778b641cf23e3f5c6d6212cf412b ]

Ritesh reported a bug [1] against UML, noting that it crashed on
startup. The backtrace shows the following (heavily redacted):

(gdb) bt
...
 #26 0x0000000060015b5d in sem_init () at ipc/sem.c:268
 #27 0x00007f89906d92f7 in ?? () from /lib/x86_64-linux-gnu/libcom_err.so.2
 #28 0x00007f8990ab8fb2 in call_init (...) at dl-init.c:72
...
 #40 0x00007f89909bf3a6 in nss_load_library (...) at nsswitch.c:359
...
 #44 0x00007f8990895e35 in _nss_compat_getgrnam_r (...) at nss_compat/compat-grp.c:486
 #45 0x00007f8990968b85 in __getgrnam_r [...]
 #46 0x00007f89909d6b77 in grantpt [...]
 #47 0x00007f8990a9394e in __GI_openpty [...]
 #48 0x00000000604a1f65 in openpty_cb (...) at arch/um/os-Linux/sigio.c:407
 #49 0x00000000604a58d0 in start_idle_thread (...) at arch/um/os-Linux/skas/process.c:598
 #50 0x0000000060004a3d in start_uml () at arch/um/kernel/skas/process.c:45
 #51 0x00000000600047b2 in linux_main (...) at arch/um/kernel/um_arch.c:334
 #52 0x000000006000574f in main (...) at arch/um/os-Linux/main.c:144

indicating that the UML function openpty_cb() calls openpty(),
which internally calls __getgrnam_r(), which causes the nsswitch
machinery to get started.

This loads, through lots of indirection that I snipped, the
libcom_err.so.2 library, which (in an unknown function, "??")
calls sem_init().

Now, of course it wants to get libpthread's sem_init(), since
it's linked against libpthread. However, the dynamic linker
looks up that symbol against the binary first, and gets the
kernel's sem_init().

Hajime Tazaki noted that "objcopy -L" can localize a symbol,
so the dynamic linker wouldn't do the lookup this way. I tried,
but for some reason that didn't seem to work.

Doing the same thing in the linker script instead does seem to
work, though I cannot entirely explain - it *also* works if I
just add "VERSION { { global: *; }; }" instead, indicating that
something else is happening that I don't really understand. It
may be that explicitly doing that marks them with some kind of
empty version, and that's different from the default.

Explicitly marking them with a version breaks kallsyms, so that
doesn't seem to be possible.

Marking all the symbols as local seems correct, and does seem
to address the issue, so do that. Also do it for static link,
nsswitch libraries could still be loaded there.

[1] https://bugs.debian.org/983379

Reported-by: Ritesh Raj Sarraf 
Signed-off-by: Johannes Berg 
Acked-By: Anton Ivanov 
Tested-By: Ritesh Raj Sarraf 
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: mm: check more comprehensively for stub changes

2021-03-04T09:26:50+00:00

commit 47da29763ec9a153b9b685bff9db659e4e09e494 upstream.

If userspace tries to change the stub, we need to kill it,
because otherwise it can escape the virtual machine. In a
few cases the stub checks weren't good, e.g. if userspace
just tries to

	mmap(0x100000 - 0x1000, 0x3000, ...)

it could succeed to get a new private/anonymous mapping
replacing the stubs. Fix this by checking everywhere, and
checking for _overlap_, not just direct changes.

Cc: stable@vger.kernel.org
Fixes: 3963333fe676 ("uml: cover stubs with a VMA")
Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger 
Signed-off-by: Greg Kroah-Hartman

um: virtio: free vu_dev only with the contained struct device

2021-02-10T08:25:27+00:00

[ Upstream commit f4172b084342fd3f9e38c10650ffe19eac30d8ce ]

Since struct device is refcounted, we shouldn't free the vu_dev
immediately when it's removed from the platform device, but only
when the references actually all go away. Move the freeing to
the release to accomplish that.

Fixes: 5d38f324993f ("um: drivers: Add virtio vhost-user driver")
Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: ubd: Submit all data segments atomically

2021-01-06T13:48:40+00:00

[ Upstream commit fc6b6a872dcd48c6f39c7975836d75113db67d37 ]

Internally, UBD treats each physical IO segment as a separate command to
be submitted in the execution pipe.  If the pipe returns a transient
error after a few segments have already been written, UBD will tell the
block layer to requeue the request, but there is no way to reclaim the
segments already submitted.  When a new attempt to dispatch the request
is done, those segments already submitted will get duplicated, causing
the WARN_ON below in the best case, and potentially data corruption.

In my system, running a UML instance with 2GB of RAM and a 50M UBD disk,
I can reproduce the WARN_ON by simply running mkfs.fvat against the
disk on a freshly booted system.

There are a few ways to around this, like reducing the pressure on
the pipe by reducing the queue depth, which almost eliminates the
occurrence of the problem, increasing the pipe buffer size on the host
system, or by limiting the request to one physical segment, which causes
the block layer to submit way more requests to resolve a single
operation.

Instead, this patch modifies the format of a UBD command, such that all
segments are sent through a single element in the communication pipe,
turning the command submission atomic from the point of view of the
block layer.  The new format has a variable size, depending on the
number of elements, and looks like this:

+------------+-----------+-----------+------------
| cmd_header | segment 0 | segment 1 | segment ...
+------------+-----------+-----------+------------

With this format, we push a pointer to cmd_header in the submission
pipe.

This has the advantage of reducing the memory footprint of executing a
single request, since it allow us to merge some fields in the header.
It is possible to reduce even further each segment memory footprint, by
merging bitmap_words and cow_offset, for instance, but this is not the
focus of this patch and is left as future work.  One issue with the
patch is that for a big number of segments, we now perform one big
memory allocation instead of multiple small ones, but I wasn't able to
trigger any real issues or -ENOMEM because of this change, that wouldn't
be reproduced otherwise.

This was tested using fio with the verify-crc32 option, and by running
an ext4 filesystem over this UBD device.

The original WARN_ON was:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at lib/refcount.c:28 refcount_warn_saturate+0x13f/0x141
refcount_t: underflow; use-after-free.
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.5.0-rc6-00002-g2a5bb2cf75c8 #346
Stack:
 6084eed0 6063dc77 00000009 6084ef60
 00000000 604b8d9f 6084eee0 6063dcbc
 6084ef40 6006ab8d e013d780 1c00000000
Call Trace:
 [<600a0c1c>] ? printk+0x0/0x94
 [<6004a888>] show_stack+0x13b/0x155
 [<6063dc77>] ? dump_stack_print_info+0xdf/0xe8
 [<604b8d9f>] ? refcount_warn_saturate+0x13f/0x141
 [<6063dcbc>] dump_stack+0x2a/0x2c
 [<6006ab8d>] __warn+0x107/0x134
 [<6008da6c>] ? wake_up_process+0x17/0x19
 [<60487628>] ? blk_queue_max_discard_sectors+0x0/0xd
 [<6006b05f>] warn_slowpath_fmt+0xd1/0xdf
 [<6006af8e>] ? warn_slowpath_fmt+0x0/0xdf
 [<600acc14>] ? raw_read_seqcount_begin.constprop.0+0x0/0x15
 [<600619ae>] ? os_nsecs+0x1d/0x2b
 [<604b8d9f>] refcount_warn_saturate+0x13f/0x141
 [<6048bc8f>] refcount_sub_and_test.constprop.0+0x2f/0x37
 [<6048c8de>] blk_mq_free_request+0xf1/0x10d
 [<6048ca06>] __blk_mq_end_request+0x10c/0x114
 [<6005ac0f>] ubd_intr+0xb5/0x169
 [<600a1a37>] __handle_irq_event_percpu+0x6b/0x17e
 [<600a1b70>] handle_irq_event_percpu+0x26/0x69
 [<600a1bd9>] handle_irq_event+0x26/0x34
 [<600a1bb3>] ? handle_irq_event+0x0/0x34
 [<600a5186>] ? unmask_irq+0x0/0x37
 [<600a57e6>] handle_edge_irq+0xbc/0xd6
 [<600a131a>] generic_handle_irq+0x21/0x29
 [<60048f6e>] do_IRQ+0x39/0x54
 [...]
---[ end trace c6e7444e55386c0f ]---

Cc: Christopher Obbard 
Reported-by: Martyn Welch 
Signed-off-by: Gabriel Krisman Bertazi 
Tested-by: Christopher Obbard 
Acked-by: Anton Ivanov 
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: Remove use of asprinf in umid.c

2020-12-30T10:51:39+00:00

commit 97be7ceaf7fea68104824b6aa874cff235333ac1 upstream.

asprintf is not compatible with the existing uml memory allocation
mechanism. Its use on the "user" side of UML results in a corrupt slab
state.

Fixes: 0d4e5ac7e780 ("um: remove uses of variable length arrays")
Cc: stable@vger.kernel.org
Signed-off-by: Anton Ivanov 
Signed-off-by: Richard Weinberger 
Signed-off-by: Greg Kroah-Hartman

um: chan_xterm: Fix fd leak

2020-12-30T10:51:26+00:00

[ Upstream commit 9431f7c199ab0d02da1482d62255e0b4621cb1b5 ]

xterm serial channel was leaking a fd used in setting up the
port helper

This bug is prehistoric - it predates switching to git. The "fixes"
header here is really just to mark all the versions we would like this to
apply to which is "Anything from the Cretaceous period onwards".

No dinosaurs were harmed in fixing this bug.

Fixes: b40997b872cd ("um: drivers/xterm.c: fix a file descriptor leak")
Signed-off-by: Anton Ivanov 
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: tty: Fix handling of close in tty lines

2020-12-30T10:51:26+00:00

[ Upstream commit 9b1c0c0e25dcccafd30e7d4c150c249cc65550eb ]

Fix a logical error in tty reading. We get 0 and errno == EAGAIN
on the first attempt to read from a closed file descriptor.

Compared to that a true EAGAIN is EAGAIN and -1.

If we check errno for EAGAIN first, before checking the return
value we miss the fact that the descriptor is closed.

This bug is as old as the driver. It was not showing up with
the original POLL based IRQ controller, because it was
producing multiple events. Switching to EPOLL unmasked it.

Fixes: ff6a17989c08 ("Epoll based IRQ controller")
Signed-off-by: Anton Ivanov 
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin