This patch addresses CVE-2024-49935 [1], a vulnerability in ACPI subsystem caused by calling cpumask_clear_cpu() with bit to clear set to 0xffffffff, thus leading to erroneous memory access. The issue is still present in 5.10.y kernel.
The original commit [2] has been backported to several stable branches (5.15.y and fresher) and now has been cherry-picked for 5.10.y.
[1] https://nvd.nist.gov/vuln/detail/CVE-2024-49935 [2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
Seiji Nishikawa (1): ACPI: PAD: fix crash in exit_round_robin()
drivers/acpi/acpi_pad.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
From: Seiji Nishikawa snishika@redhat.com
[ Upstream commit 0a2ed70a549e61c5181bad5db418d223b68ae932 ]
The kernel occasionally crashes in cpumask_clear_cpu(), which is called within exit_round_robin(), because when executing clear_bit(nr, addr) with nr set to 0xffffffff, the address calculation may cause misalignment within the memory, leading to access to an invalid memory address.
---------- BUG: unable to handle kernel paging request at ffffffffe0740618 ... CPU: 3 PID: 2919323 Comm: acpi_pad/14 Kdump: loaded Tainted: G OE X --------- - - 4.18.0-425.19.2.el8_7.x86_64 #1 ... RIP: 0010:power_saving_thread+0x313/0x411 [acpi_pad] Code: 89 cd 48 89 d3 eb d1 48 c7 c7 55 70 72 c0 e8 64 86 b0 e4 c6 05 0d a1 02 00 01 e9 bc fd ff ff 45 89 e4 42 8b 04 a5 20 82 72 c0 <f0> 48 0f b3 05 f4 9c 01 00 42 c7 04 a5 20 82 72 c0 ff ff ff ff 31 RSP: 0018:ff72a5d51fa77ec8 EFLAGS: 00010202 RAX: 00000000ffffffff RBX: ff462981e5d8cb80 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000246 RDI: 0000000000000246 RBP: ff46297556959d80 R08: 0000000000000382 R09: ff46297c8d0f38d8 R10: 0000000000000000 R11: 0000000000000001 R12: 000000000000000e R13: 0000000000000000 R14: ffffffffffffffff R15: 000000000000000e FS: 0000000000000000(0000) GS:ff46297a800c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffe0740618 CR3: 0000007e20410004 CR4: 0000000000771ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: ? acpi_pad_add+0x120/0x120 [acpi_pad] kthread+0x10b/0x130 ? set_kthread_struct+0x50/0x50 ret_from_fork+0x1f/0x40 ... CR2: ffffffffe0740618
crash> dis -lr ffffffffc0726923 ... /usr/src/debug/kernel-4.18.0-425.19.2.el8_7/linux-4.18.0-425.19.2.el8_7.x86_64/./include/linux/cpumask.h: 114 0xffffffffc0726918 <power_saving_thread+776>: mov %r12d,%r12d /usr/src/debug/kernel-4.18.0-425.19.2.el8_7/linux-4.18.0-425.19.2.el8_7.x86_64/./include/linux/cpumask.h: 325 0xffffffffc072691b <power_saving_thread+779>: mov -0x3f8d7de0(,%r12,4),%eax /usr/src/debug/kernel-4.18.0-425.19.2.el8_7/linux-4.18.0-425.19.2.el8_7.x86_64/./arch/x86/include/asm/bitops.h: 80 0xffffffffc0726923 <power_saving_thread+787>: lock btr %rax,0x19cf4(%rip) # 0xffffffffc0740620 <pad_busy_cpus_bits>
crash> px tsk_in_cpu[14] $66 = 0xffffffff
crash> px 0xffffffffc072692c+0x19cf4 $99 = 0xffffffffc0740620
crash> sym 0xffffffffc0740620 ffffffffc0740620 (b) pad_busy_cpus_bits [acpi_pad]
crash> px pad_busy_cpus_bits[0] $42 = 0xfffc0 ----------
To fix this, ensure that tsk_in_cpu[tsk_index] != -1 before calling cpumask_clear_cpu() in exit_round_robin(), just as it is done in round_robin_cpu().
Signed-off-by: Seiji Nishikawa snishika@redhat.com Link: https://patch.msgid.link/20240825141352.25280-1-snishika@redhat.com [ rjw: Subject edit, avoid updates to the same value ] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com [ Nikita: fix conflict due to missing blank line from commit c8eb628cbdd9 ("ACPI: acpi_pad: add a missed blank line after declarations"). ] Signed-off-by: Nikita Zhandarovich n.zhandarovich@fintech.ru --- drivers/acpi/acpi_pad.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c index b84ab722feb4..6d592d8655cd 100644 --- a/drivers/acpi/acpi_pad.c +++ b/drivers/acpi/acpi_pad.c @@ -128,8 +128,11 @@ static void round_robin_cpu(unsigned int tsk_index) static void exit_round_robin(unsigned int tsk_index) { struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); - cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); - tsk_in_cpu[tsk_index] = -1; + + if (tsk_in_cpu[tsk_index] != -1) { + cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); + tsk_in_cpu[tsk_index] = -1; + } }
static unsigned int idle_pct = 5; /* percentage */
[ Sasha's backport helper bot ]
Hi,
The upstream commit SHA1 provided is correct: 0a2ed70a549e61c5181bad5db418d223b68ae932
WARNING: Author mismatch between patch and upstream commit: Backport author: Nikita Zhandarovich n.zhandarovich@fintech.ru Commit author: Seiji Nishikawa snishika@redhat.com
Status in newer kernel trees: 6.12.y | Present (exact SHA1) 6.11.y | Present (different SHA1: 27c045f868f0) 6.6.y | Present (different SHA1: 68a8e45743d6) 6.1.y | Present (different SHA1: 68a599da16eb) 5.15.y | Present (different SHA1: 92e5661b7d07) 5.10.y | Not found
Note: The patch differs from the upstream commit: --- 1: 0a2ed70a549e6 ! 1: fa503f92cd35f ACPI: PAD: fix crash in exit_round_robin() @@ Metadata ## Commit message ## ACPI: PAD: fix crash in exit_round_robin()
+ [ Upstream commit 0a2ed70a549e61c5181bad5db418d223b68ae932 ] + The kernel occasionally crashes in cpumask_clear_cpu(), which is called within exit_round_robin(), because when executing clear_bit(nr, addr) with nr set to 0xffffffff, the address calculation may cause misalignment within @@ Commit message Link: https://patch.msgid.link/20240825141352.25280-1-snishika@redhat.com [ rjw: Subject edit, avoid updates to the same value ] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com + [ Nikita: fix conflict due to missing blank line from commit + c8eb628cbdd9 ("ACPI: acpi_pad: add a missed blank line after + declarations"). ] + Signed-off-by: Nikita Zhandarovich n.zhandarovich@fintech.ru
## drivers/acpi/acpi_pad.c ## -@@ drivers/acpi/acpi_pad.c: static void exit_round_robin(unsigned int tsk_index) +@@ drivers/acpi/acpi_pad.c: static void round_robin_cpu(unsigned int tsk_index) + static void exit_round_robin(unsigned int tsk_index) { struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); - - cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); - tsk_in_cpu[tsk_index] = -1; ++ + if (tsk_in_cpu[tsk_index] != -1) { + cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); + tsk_in_cpu[tsk_index] = -1; ---
Results of testing on various branches:
| Branch | Patch Apply | Build Test | |---------------------------|-------------|------------| | stable/linux-5.10.y | Success | Success |
linux-stable-mirror@lists.linaro.org
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Nikita Zhandarovich -
Sasha Levin