On Thu, Apr 04, 2024 at 12:32:53PM -0400, Rik van Riel wrote: > 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. > > Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx> > Cc: Tejun Heo <tj@xxxxxxxxxx> > Cc: Josef Bacik <josef@xxxxxxxxxxxxxx> > Cc: Jens Axboe <axboe@xxxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun
