| Message ID | 20240404123253.0f58010f@imladris.surriel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | blk-iocost: avoid out of bounds shift | expand |
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@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> Thanks.
On Thu, 04 Apr 2024 12:32:53 -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 > ... > > [...] Applied, thanks! [1/1] blk-iocost: avoid out of bounds shift commit: beaa51b36012fad5a4d3c18b88a617aea7a9b96d Best regards,
diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 9a85bfbbc45a..baa20c85799d 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -1347,7 +1347,7 @@ 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; @@ -1362,8 +1362,9 @@ 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;
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> --- block/blk-iocost.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)