6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Khazhismel Kumykov <khazhy@xxxxxxxxxxxx>
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: 8d6bbaada2e0 ("blk-throttle: prevent overflow while calculating wait time")
Signed-off-by: Khazhismel Kumykov <khazhy@xxxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231020223617.2739774-1-khazhy@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
block/blk-throttle.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -723,6 +723,12 @@ static unsigned int calculate_io_allowed
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);
}
