Vulnerability CVE-2023-52791
Published: 2024-05-21

Description:
In the Linux kernel, the following vulnerability has been resolved:

i2c: core: Run atomic i2c xfer when !preemptible

Since bae1d3a05a8b, i2c transfers are non-atomic if preemption is
disabled. However, non-atomic i2c transfers require preemption (e.g. in
wait_for_completion() while waiting for the DMA).

panic() calls preempt_disable_notrace() before calling
emergency_restart(). Therefore, if an i2c device is used for the
restart, the xfer should be atomic. This avoids warnings like:

[ 12.667612] WARNING: CPU: 1 PID: 1 at kernel/rcu/tree_plugin.h:318 rcu_note_context_switch+0x33c/0x6b0
[ 12.676926] Voluntary context switch within RCU read-side critical section!
...
[ 12.742376] schedule_timeout from wait_for_completion_timeout+0x90/0x114
[ 12.749179] wait_for_completion_timeout from tegra_i2c_wait_completion+0x40/0x70
...
[ 12.994527] atomic_notifier_call_chain from machine_restart+0x34/0x58
[ 13.001050] machine_restart from panic+0x2a8/0x32c

Use !preemptible() instead, which is basically the same check as
pre-v5.2.

 References:
https://git.kernel.org/stable/c/25eb381a736e7ae39a4245ef5c96484eb1073809
https://git.kernel.org/stable/c/25284c46b657f48c0f3880a2e0706c70d81182c0
https://git.kernel.org/stable/c/f6237afabc349c1c7909db00e15d2816519e0d2b
https://git.kernel.org/stable/c/185f3617adc8fe45e40489b458f03911f0dec46c
https://git.kernel.org/stable/c/8c3fa52a46ff4d208cefb1a462ec94e0043a91e1
https://git.kernel.org/stable/c/3473cf43b9068b9dfef2f545f833f33c6a544b91
https://git.kernel.org/stable/c/aa49c90894d06e18a1ee7c095edbd2f37c232d02
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