CVE-2024-36916

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.