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blk-throttle: check for overflow in calculate_bytes_allowed

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commit 2dd710d476f2f1f6eaca884f625f69ef4389ed40 upstream.

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: 8d6bbaada2 ("blk-throttle: prevent overflow while calculating wait time")
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20231020223617.2739774-1-khazhy@google.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Khazhismel Kumykov 2023-10-20 15:36:17 -07:00 committed by Greg Kroah-Hartman
parent bb20a245df
commit 6a5b845b57
1 changed files with 6 additions and 0 deletions
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6
block/blk-throttle.c
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@ -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);
}