linux-stable.git/Documentation, branch v5.4.258

perf/smmuv3: Enable HiSilicon Erratum 162001900 quirk for HIP08/09

2023-09-23T09:00:03+00:00

[ Upstream commit 0242737dc4eb9f6e9a5ea594b3f93efa0b12f28d ]

Some HiSilicon SMMU PMCG suffers the erratum 162001900 that the PMU
disable control sometimes fail to disable the counters. This will lead
to error or inaccurate data since before we enable the counters the
counter's still counting for the event used in last perf session.

This patch tries to fix this by hardening the global disable process.
Before disable the PMU, writing an invalid event type (0xffff) to
focibly stop the counters. Correspondingly restore each events on
pmu::pmu_enable().

Signed-off-by: Yicong Yang 
Link: https://lore.kernel.org/r/20230814124012.58013-1-yangyicong@huawei.com
Signed-off-by: Will Deacon 
Signed-off-by: Sasha Levin

Documentation/sysctl: document page_lock_unfairness

2023-08-30T14:27:27+00:00

commit 8d98e42fb20c25e8efdab4cc1ac46d52ba964aca upstream.

commit 5ef64cc8987a ("mm: allow a controlled amount of unfairness in the
page lock") introduced a new systctl but no accompanying documentation.

Add a simple entry to the documentation.

Link: https://lkml.kernel.org/r/20220325164437.120246-1-jsavitz@redhat.com
Signed-off-by: Joel Savitz 
Cc: Jonathan Corbet 
Cc: Vlastimil Babka 
Cc: Mel Gorman 
Cc: Dave Hansen 
Cc: Suren Baghdasaryan 
Cc: Mike Rapoport 
Cc: "zhangyi (F)" 
Cc: Charan Teja Reddy 
Cc: Linus Torvalds 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

PM: runtime: Add pm_runtime_get_if_active()

2023-08-30T14:27:12+00:00

[ Upstream commit c111566bea7ccd8a05e2c56f1fb3cbb6f4b7b441 ]

pm_runtime_get_if_in_use() bumps up the PM-runtime usage count if it
is not equal to zero and the device's PM-runtime status is 'active'.
This works for drivers that do not use autoidle, but for those that
do, the function returns zero even when the device is active.

In order to maintain sane device state while the device is powered on
in the hope that it'll be needed, pm_runtime_get_if_active(dev, true)
returns a positive value if the device's PM-runtime status is 'active'
when it is called, in which case it also increments the device's usage
count.

If the second argument of pm_runtime_get_if_active() is 'false', the
function behaves just like pm_runtime_get_if_in_use(), so redefine
the latter as a wrapper around the former.

Signed-off-by: Sakari Ailus 
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki 
Stable-dep-of: 81302b1c7c99 ("ALSA: hda: Fix unhandled register update during auto-suspend period")
Signed-off-by: Sasha Levin

Documentation: security-bugs.rst: clarify CVE handling

2023-08-11T09:53:52+00:00

commit 3c1897ae4b6bc7cc586eda2feaa2cd68325ec29c upstream.

The kernel security team does NOT assign CVEs, so document that properly
and provide the "if you want one, ask MITRE for it" response that we
give on a weekly basis in the document, so we don't have to constantly
say it to everyone who asks.

Link: https://lore.kernel.org/r/2023063022-retouch-kerosene-7e4a@gregkh
Signed-off-by: Greg Kroah-Hartman

Documentation: security-bugs.rst: update preferences when dealing with the linux-distros group

2023-08-11T09:53:51+00:00

commit 4fee0915e649bd0cea56dece6d96f8f4643df33c upstream.

Because the linux-distros group forces reporters to release information
about reported bugs, and they impose arbitrary deadlines in having those
bugs fixed despite not actually being kernel developers, the kernel
security team recommends not interacting with them at all as this just
causes confusion and the early-release of reported security problems.

Reviewed-by: Kees Cook 
Link: https://lore.kernel.org/r/2023063020-throat-pantyhose-f110@gregkh
Signed-off-by: Greg Kroah-Hartman

Documentation/x86: Fix backwards on/off logic about YMM support

2023-08-08T17:56:36+00:00

commit 1b0fc0345f2852ffe54fb9ae0e12e2ee69ad6a20 upstream

These options clearly turn *off* XSAVE YMM support.  Correct the
typo.

Reported-by: Ben Hutchings 
Fixes: 553a5c03e90a ("x86/speculation: Add force option to GDS mitigation")
Signed-off-by: Dave Hansen 
Signed-off-by: Greg Kroah-Hartman

x86/speculation: Add force option to GDS mitigation

2023-08-08T17:56:35+00:00

commit 553a5c03e90a6087e88f8ff878335ef0621536fb upstream

The Gather Data Sampling (GDS) vulnerability allows malicious software
to infer stale data previously stored in vector registers. This may
include sensitive data such as cryptographic keys. GDS is mitigated in
microcode, and systems with up-to-date microcode are protected by
default. However, any affected system that is running with older
microcode will still be vulnerable to GDS attacks.

Since the gather instructions used by the attacker are part of the
AVX2 and AVX512 extensions, disabling these extensions prevents gather
instructions from being executed, thereby mitigating the system from
GDS. Disabling AVX2 is sufficient, but we don't have the granularity
to do this. The XCR0[2] disables AVX, with no option to just disable
AVX2.

Add a kernel parameter gather_data_sampling=force that will enable the
microcode mitigation if available, otherwise it will disable AVX on
affected systems.

This option will be ignored if cmdline mitigations=off.

This is a *big* hammer.  It is known to break buggy userspace that
uses incomplete, buggy AVX enumeration.  Unfortunately, such userspace
does exist in the wild:

	https://www.mail-archive.com/bug-coreutils@gnu.org/msg33046.html

[ dhansen: add some more ominous warnings about disabling AVX ]

Signed-off-by: Daniel Sneddon 
Signed-off-by: Dave Hansen 
Acked-by: Josh Poimboeuf 
Signed-off-by: Daniel Sneddon 
Signed-off-by: Greg Kroah-Hartman

x86/speculation: Add Gather Data Sampling mitigation

2023-08-08T17:56:35+00:00

commit 8974eb588283b7d44a7c91fa09fcbaf380339f3a upstream

Gather Data Sampling (GDS) is a hardware vulnerability which allows
unprivileged speculative access to data which was previously stored in
vector registers.

Intel processors that support AVX2 and AVX512 have gather instructions
that fetch non-contiguous data elements from memory. On vulnerable
hardware, when a gather instruction is transiently executed and
encounters a fault, stale data from architectural or internal vector
registers may get transiently stored to the destination vector
register allowing an attacker to infer the stale data using typical
side channel techniques like cache timing attacks.

This mitigation is different from many earlier ones for two reasons.
First, it is enabled by default and a bit must be set to *DISABLE* it.
This is the opposite of normal mitigation polarity. This means GDS can
be mitigated simply by updating microcode and leaving the new control
bit alone.

Second, GDS has a "lock" bit. This lock bit is there because the
mitigation affects the hardware security features KeyLocker and SGX.
It needs to be enabled and *STAY* enabled for these features to be
mitigated against GDS.

The mitigation is enabled in the microcode by default. Disable it by
setting gather_data_sampling=off or by disabling all mitigations with
mitigations=off. The mitigation status can be checked by reading:

    /sys/devices/system/cpu/vulnerabilities/gather_data_sampling

Signed-off-by: Daniel Sneddon 
Signed-off-by: Dave Hansen 
Acked-by: Josh Poimboeuf 
Signed-off-by: Daniel Sneddon 
Signed-off-by: Greg Kroah-Hartman

fs: Lock moved directories

2023-07-27T06:37:26+00:00

commit 28eceeda130f5058074dd007d9c59d2e8bc5af2e upstream.

When a directory is moved to a different directory, some filesystems
(udf, ext4, ocfs2, f2fs, and likely gfs2, reiserfs, and others) need to
update their pointer to the parent and this must not race with other
operations on the directory. Lock the directories when they are moved.
Although not all filesystems need this locking, we perform it in
vfs_rename() because getting the lock ordering right is really difficult
and we don't want to expose these locking details to filesystems.

CC: stable@vger.kernel.org
Signed-off-by: Jan Kara 
Message-Id: <20230601105830.13168-5-jack@suse.cz>
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

xsk: Honor SO_BINDTODEVICE on bind

2023-07-27T06:37:23+00:00

[ Upstream commit f7306acec9aae9893d15e745c8791124d42ab10a ]

Initial creation of an AF_XDP socket requires CAP_NET_RAW capability. A
privileged process might create the socket and pass it to a non-privileged
process for later use. However, that process will be able to bind the socket
to any network interface. Even though it will not be able to receive any
traffic without modification of the BPF map, the situation is not ideal.

Sockets already have a mechanism that can be used to restrict what interface
they can be attached to. That is SO_BINDTODEVICE.

To change the SO_BINDTODEVICE binding the process will need CAP_NET_RAW.

Make xsk_bind() honor the SO_BINDTODEVICE in order to allow safer workflow
when non-privileged process is using AF_XDP.

The intended workflow is following:

  1. First process creates a bare socket with socket(AF_XDP, ...).
  2. First process loads the XSK program to the interface.
  3. First process adds the socket fd to a BPF map.
  4. First process ties socket fd to a particular interface using
     SO_BINDTODEVICE.
  5. First process sends socket fd to a second process.
  6. Second process allocates UMEM.
  7. Second process binds socket to the interface with bind(...).
  8. Second process sends/receives the traffic.

All the steps above are possible today if the first process is privileged
and the second one has sufficient RLIMIT_MEMLOCK and no capabilities.
However, the second process will be able to bind the socket to any interface
it wants on step 7 and send traffic from it. With the proposed change, the
second process will be able to bind the socket only to a specific interface
chosen by the first process at step 4.

Fixes: 965a99098443 ("xsk: add support for bind for Rx")
Signed-off-by: Ilya Maximets 
Signed-off-by: Daniel Borkmann 
Acked-by: Magnus Karlsson 
Acked-by: John Fastabend 
Acked-by: Jason Wang 
Link: https://lore.kernel.org/bpf/20230703175329.3259672-1-i.maximets@ovn.org
Signed-off-by: Sasha Levin