Vulnerability CVE-2024-36916
Published: 2024-05-30

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

blk-iocost: avoid out of bounds shift

UBSAN catches undefined behavior in blk-iocost, where sometimes
iocg->delay is shifted right by a number that is too large,
resulting in undefined behavior on some architectures.

[ 186.556576] ------------[ cut here ]------------
UBSAN: shift-out-of-bounds in block/blk-iocost.c:1366:23
shift exponent 64 is too large for 64-bit type 'u64' (aka 'unsigned long long')
CPU: 16 PID: 0 Comm: swapper/16 Tainted: G S E N 6.9.0-0_fbk700_debug_rc2_kbuilder_0_gc85af715cac0 #1
Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A23 12/08/2020
Call Trace:
<IRQ>
dump_stack_lvl+0x8f/0xe0
__ubsan_handle_shift_out_of_bounds+0x22c/0x280
iocg_kick_delay+0x30b/0x310
ioc_timer_fn+0x2fb/0x1f80
__run_timer_base+0x1b6/0x250
...

Avoid that undefined behavior by simply taking the
"delay = 0" branch if the shift is too large.

I am not sure what the symptoms of an undefined value
delay will be, but I suspect it could be more than a
little annoying to debug.

 References:
https://git.kernel.org/stable/c/62accf6c1d7b433752cb3591bba8967b7a801ad5
https://git.kernel.org/stable/c/844fc023e9f14a4fb1de5ae1eaefafd6d69c5fa1
https://git.kernel.org/stable/c/f6add0a6f78dc6360b822ca4b6f9f2f14174c8ca
https://git.kernel.org/stable/c/ce0e99cae00e3131872936713b7f55eefd53ab86
https://git.kernel.org/stable/c/488dc6808cb8369685f18cee81e88e7052ac153b
https://git.kernel.org/stable/c/beaa51b36012fad5a4d3c18b88a617aea7a9b96d
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