| Message ID | 20231020223617.2739774-1-khazhy@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | blk-throttle: check for overflow in calculate_bytes_allowed | expand |
On Fri, Oct 20, 2023 at 03:36:17PM -0700, Khazhismel Kumykov wrote: > Inexact, we may reject some not-overflowing values incorrectly, but > they'll be on the order of exabytes allowed anyways. > > This fixes divide error crash on x86 if bps_limit is not configured or > is set too high in the rare case that jiffy_elapsed is greater than HZ. > > Fixes: e8368b57c006 ("blk-throttle: use calculate_io/bytes_allowed() for throtl_trim_slice()") > Fixes: 8d6bbaada2e0 ("blk-throttle: prevent overflow while calculating wait time") > Signed-off-by: Khazhismel Kumykov <khazhy@google.com> Acked-by: Tejun Heo <tj@kernel.org> Thanks.
On Fri, 20 Oct 2023 15:36:17 -0700, Khazhismel Kumykov wrote: > Inexact, we may reject some not-overflowing values incorrectly, but > they'll be on the order of exabytes allowed anyways. > > This fixes divide error crash on x86 if bps_limit is not configured or > is set too high in the rare case that jiffy_elapsed is greater than HZ. > > > [...] Applied, thanks! [1/1] blk-throttle: check for overflow in calculate_bytes_allowed commit: 2dd710d476f2f1f6eaca884f625f69ef4389ed40 Best regards,
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 38a881cf97d0..13e4377a8b28 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -723,6 +723,12 @@ static unsigned int calculate_io_allowed(u32 iops_limit, static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed) { + /* + * Can result be wider than 64 bits? + * We check against 62, not 64, due to ilog2 truncation. + */ + if (ilog2(bps_limit) + ilog2(jiffy_elapsed) - ilog2(HZ) > 62) + return U64_MAX; return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ); }
Inexact, we may reject some not-overflowing values incorrectly, but they'll be on the order of exabytes allowed anyways. This fixes divide error crash on x86 if bps_limit is not configured or is set too high in the rare case that jiffy_elapsed is greater than HZ. Fixes: e8368b57c006 ("blk-throttle: use calculate_io/bytes_allowed() for throtl_trim_slice()") Fixes: 8d6bbaada2e0 ("blk-throttle: prevent overflow while calculating wait time") Signed-off-by: Khazhismel Kumykov <khazhy@google.com> --- block/blk-throttle.c | 6 ++++++ 1 file changed, 6 insertions(+)