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 6.9.0-0fbk700debugrc2kbuilder0gc85af715cac0 #1 Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F093A23 12/08/2020 Call Trace: <IRQ> dumpstacklvl+0x8f/0xe0 _ubsanhandleshiftoutofbounds+0x22c/0x280 iocgkickdelay+0x30b/0x310 ioctimerfn+0x2fb/0x1f80 _runtimerbase+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.