6.1-stable review patch. If anyone has any objections, please let me know.
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From: Khazhismel Kumykov khazhy@chromium.org
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@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 --- 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); }