CVE-2024-49935: ACPI: PAD: fix crash in exit_round_robin()

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

ACPI: PAD: fix crash in exitroundrobin()

The kernel occasionally crashes in cpumaskclearcpu(), which is called within exitroundrobin(), because when executing clearbit(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: acpipad/14 Kdump: loaded Tainted: G OE X --------- - - 4.18.0-425.19.2.el87.x8664 #1 ... RIP: 0010:powersavingthread+0x313/0x411 [acpipad] 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: ? acpipadadd+0x120/0x120 [acpipad] kthread+0x10b/0x130 ? setkthreadstruct+0x50/0x50 retfromfork+0x1f/0x40 ... CR2: ffffffffe0740618

crash> dis -lr ffffffffc0726923 ... /usr/src/debug/kernel-4.18.0-425.19.2.el87/linux-4.18.0-425.19.2.el87.x8664/./include/linux/cpumask.h: 114 0xffffffffc0726918 <powersavingthread+776>: mov %r12d,%r12d /usr/src/debug/kernel-4.18.0-425.19.2.el87/linux-4.18.0-425.19.2.el87.x8664/./include/linux/cpumask.h: 325 0xffffffffc072691b <powersavingthread+779>: mov -0x3f8d7de0(,%r12,4),%eax /usr/src/debug/kernel-4.18.0-425.19.2.el87/linux-4.18.0-425.19.2.el87.x8664/./arch/x86/include/asm/bitops.h: 80 0xffffffffc0726923 <powersavingthread+787>: lock btr %rax,0x19cf4(%rip) # 0xffffffffc0740620 <padbusycpusbits>

crash> px tskincpu[14] $66 = 0xffffffff

crash> px 0xffffffffc072692c+0x19cf4 $99 = 0xffffffffc0740620

crash> sym 0xffffffffc0740620 ffffffffc0740620 (b) padbusycpusbits [acpipad]

crash> px padbusycpusbits[0] $42 = 0xfffc0 ----------

To fix this, ensure that tskincpu[tskindex] != -1 before calling cpumaskclearcpu() in exitroundrobin(), just as it is done in roundrobincpu().

[ rjw: Subject edit, avoid updates to the same value ]

— NVD

This CVE was automatically created from a reference found in an email or other text. If you are reading this, then this CVE entry is probably erroneous, since this text should be replaced by the official CVE description automatically.

— Launchpad