Description

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

blk_iocost: fix more out of bound shifts

Recently running UBSAN caught few out of bound shifts in the
ioc_forgive_debts() function:

UBSAN: shift-out-of-bounds in block/blk-iocost.c:2142:38
shift exponent 80 is too large for 64-bit type 'u64' (aka 'unsigned long
long')
...
UBSAN: shift-out-of-bounds in block/blk-iocost.c:2144:30
shift exponent 80 is too large for 64-bit type 'u64' (aka 'unsigned long
long')
...
Call Trace:

dump_stack_lvl+0xca/0x130
__ubsan_handle_shift_out_of_bounds+0x22c/0x280
? __lock_acquire+0x6441/0x7c10
ioc_timer_fn+0x6cec/0x7750
? blk_iocost_init+0x720/0x720
? call_timer_fn+0x5d/0x470
call_timer_fn+0xfa/0x470
? blk_iocost_init+0x720/0x720
__run_timer_base+0x519/0x700
...

Actual impact of this issue was not identified but I propose to fix the
undefined behaviour.
The proposed fix to prevent those out of bound shifts consist of
precalculating exponent before using it the shift operations by taking
min value from the actual exponent and maximum possible number of bits.

Classification

CVE ID: CVE-2024-49933

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 5.08% (scored less or equal to compared to others)

EPSS Date: 2025-02-04 (when was this score calculated)

References

https://git.kernel.org/stable/c/1f61d509257d6a05763d05bf37943b35306522b1
https://git.kernel.org/stable/c/f4ef9bef023d5c543cb0f3194ecacfd47ef590ec
https://git.kernel.org/stable/c/59121bb38fdc01434ea3fe361ee02b59f036227f
https://git.kernel.org/stable/c/1ab2cfe19700fb3dde4c7dfec392acff34db3120
https://git.kernel.org/stable/c/1b120f151871eb47ce9f283c007af3f8ae1d990e
https://git.kernel.org/stable/c/364022095bdd4108efdaaa68576afa4712a5d085
https://git.kernel.org/stable/c/9bce8005ec0dcb23a58300e8522fe4a31da606fa

Timeline