Patch "block: prevent division by zero in blk_rq_stat_sum()" has been added to the 6.8-stable tree

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This is a note to let you know that I've just added the patch titled

    block: prevent division by zero in blk_rq_stat_sum()

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     block-prevent-division-by-zero-in-blk_rq_stat_sum.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 06c0345a5dbdc0181c0c00c008c983f4d3173be4
Author: Roman Smirnov <r.smirnov@xxxxxx>
Date:   Tue Mar 5 16:45:09 2024 +0300

    block: prevent division by zero in blk_rq_stat_sum()
    
    [ Upstream commit 93f52fbeaf4b676b21acfe42a5152620e6770d02 ]
    
    The expression dst->nr_samples + src->nr_samples may
    have zero value on overflow. It is necessary to add
    a check to avoid division by zero.
    
    Found by Linux Verification Center (linuxtesting.org) with Svace.
    
    Signed-off-by: Roman Smirnov <r.smirnov@xxxxxx>
    Reviewed-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
    Link: https://lore.kernel.org/r/20240305134509.23108-1-r.smirnov@xxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/block/blk-stat.c b/block/blk-stat.c
index 7ff76ae6c76a9..e42c263e53fb9 100644
--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -27,7 +27,7 @@ void blk_rq_stat_init(struct blk_rq_stat *stat)
 /* src is a per-cpu stat, mean isn't initialized */
 void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
 {
-	if (!src->nr_samples)
+	if (dst->nr_samples + src->nr_samples <= dst->nr_samples)
 		return;
 
 	dst->min = min(dst->min, src->min);




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