From: Rik van Riel riel@surriel.com
[ Upstream commit beaa51b36012fad5a4d3c18b88a617aea7a9b96d ]
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@surriel.com Cc: Tejun Heo tj@kernel.org Cc: Josef Bacik josef@toxicpanda.com Cc: Jens Axboe axboe@kernel.dk Acked-by: Tejun Heo tj@kernel.org Link: https://lore.kernel.org/r/20240404123253.0f58010f@imladris.surriel.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-iocost.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 645a589edda82..bfdb7b0cf49de 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -1336,7 +1336,7 @@ static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now) { struct ioc *ioc = iocg->ioc; struct blkcg_gq *blkg = iocg_to_blkg(iocg); - u64 tdelta, delay, new_delay; + u64 tdelta, delay, new_delay, shift; s64 vover, vover_pct; u32 hwa;
@@ -1351,8 +1351,9 @@ static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now)
/* calculate the current delay in effect - 1/2 every second */ tdelta = now->now - iocg->delay_at; - if (iocg->delay) - delay = iocg->delay >> div64_u64(tdelta, USEC_PER_SEC); + shift = div64_u64(tdelta, USEC_PER_SEC); + if (iocg->delay && shift < BITS_PER_LONG) + delay = iocg->delay >> shift; else delay = 0;