CVE-2024-26746

In the Linux kernel, the following vulnerability has been resolved:
dmaengine: idxd: Ensure safe user copy of completion record If
CONFIG_HARDENED_USERCOPY is enabled, copying completion record from event
log cache to user triggers a kernel bug. [ 1987.159822] usercopy: Kernel
memory exposure attempt detected from SLUB object ‘dsa0’ (offset 74, size
31)! [ 1987.170845] ------------[ cut here ]------------ [ 1987.176086]
kernel BUG at mm/usercopy.c:102! [ 1987.180946] invalid opcode: 0000 [#1]
PREEMPT SMP NOPTI [ 1987.186866] CPU: 17 PID: 528 Comm: kworker/17:1 Not
tainted 6.8.0-rc2+ #5 [ 1987.194537] Hardware name: Intel Corporation
AvenueCity/AvenueCity, BIOS BHSDCRB1.86B.2492.D03.2307181620 07/18/2023 [
1987.206405] Workqueue: wq0.0 idxd_evl_fault_work [idxd] [ 1987.212338]
RIP: 0010:usercopy_abort+0x72/0x90 [ 1987.217381] Code: 58 65 9c 50 48 c7
c2 17 85 61 9c 57 48 c7 c7 98 fd 6b 9c 48 0f 44 d6 48 c7 c6 b3 08 62 9c 4c
89 d1 49 0f 44 f3 e8 1e 2e d5 ff <0f> 0b 49 c7 c1 9e 42 61 9c 4c 89 cf 4d
89 c8 eb a9 66 66 2e 0f 1f [ 1987.238505] RSP: 0018:ff62f5cf20607d60
EFLAGS: 00010246 [ 1987.244423] RAX: 000000000000005f RBX: 000000000000001f
RCX: 0000000000000000 [ 1987.252480] RDX: 0000000000000000 RSI:
ffffffff9c61429e RDI: 00000000ffffffff [ 1987.260538] RBP: ff62f5cf20607d78
R08: ff2a6a89ef3fffe8 R09: 00000000fffeffff [ 1987.268595] R10:
ff2a6a89eed00000 R11: 0000000000000003 R12: ff2a66934849c89a [ 1987.276652]
R13: 0000000000000001 R14: ff2a66934849c8b9 R15: ff2a66934849c899 [
1987.284710] FS: 0000000000000000(0000) GS:ff2a66b22fe40000(0000)
knlGS:0000000000000000 [ 1987.293850] CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033 [ 1987.300355] CR2: 00007fe291a37000 CR3: 000000010fbd4005
CR4: 0000000000f71ef0 [ 1987.308413] DR0: 0000000000000000 DR1:
0000000000000000 DR2: 0000000000000000 [ 1987.316470] DR3: 0000000000000000
DR6: 00000000fffe07f0 DR7: 0000000000000400 [ 1987.324527] PKRU: 55555554 [
1987.327622] Call Trace: [ 1987.330424] <TASK> [ 1987.332826] ?
show_regs+0x6e/0x80 [ 1987.336703] ? die+0x3c/0xa0 [ 1987.339988] ?
do_trap+0xd4/0xf0 [ 1987.343662] ? do_error_trap+0x75/0xa0 [ 1987.347922] ?
usercopy_abort+0x72/0x90 [ 1987.352277] ? exc_invalid_op+0x57/0x80 [
1987.356634] ? usercopy_abort+0x72/0x90 [ 1987.360988] ?
asm_exc_invalid_op+0x1f/0x30 [ 1987.365734] ? usercopy_abort+0x72/0x90 [
1987.370088] __check_heap_object+0xb7/0xd0 [ 1987.374739]
__check_object_size+0x175/0x2d0 [ 1987.379588] idxd_copy_cr+0xa9/0x130
[idxd] [ 1987.384341] idxd_evl_fault_work+0x127/0x390 [idxd] [ 1987.389878]
process_one_work+0x13e/0x300 [ 1987.394435] ? __pfx_worker_thread+0x10/0x10
[ 1987.399284] worker_thread+0x2f7/0x420 [ 1987.403544] ?
_raw_spin_unlock_irqrestore+0x2b/0x50 [ 1987.409171] ?
__pfx_worker_thread+0x10/0x10 [ 1987.414019] kthread+0x107/0x140 [
1987.417693] ? __pfx_kthread+0x10/0x10 [ 1987.421954]
ret_from_fork+0x3d/0x60 [ 1987.426019] ? __pfx_kthread+0x10/0x10 [
1987.430281] ret_from_fork_asm+0x1b/0x30 [ 1987.434744] </TASK> The issue
arises because event log cache is created using kmem_cache_create() which
is not suitable for user copy. Fix the issue by creating event log cache
with kmem_cache_create_usercopy(), ensuring safe user copy.