6.17-stable review patch. If anyone has any objections, please let me know.
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From: Kuan-Wei Chiu visitorckw@gmail.com
[ Upstream commit e1c4350327b39c9cad27b6c5779b3754384f26c8 ]
The comparison function cmp_loc_by_count() used for sorting stack trace locations in debugfs currently returns -1 if a->count > b->count and 1 otherwise. This breaks the antisymmetry property required by sort(), because when two counts are equal, both cmp(a, b) and cmp(b, a) return 1.
This can lead to undefined or incorrect ordering results. Fix it by updating the comparison logic to explicitly handle the case when counts are equal, and use cmp_int() to ensure the comparison function adheres to the required mathematical properties of antisymmetry.
Fixes: 553c0369b3e1 ("mm/slub: sort debugfs output by frequency of stack traces") Reviewed-by: Joshua Hahn joshua.hahnjy@gmail.com Signed-off-by: Kuan-Wei Chiu visitorckw@gmail.com Reviewed-by: Harry Yoo harry.yoo@oracle.com Signed-off-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: Sasha Levin sashal@kernel.org --- mm/slub.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c index d257141896c95..264fc76455d73 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -7731,10 +7731,7 @@ static int cmp_loc_by_count(const void *a, const void *b, const void *data) struct location *loc1 = (struct location *)a; struct location *loc2 = (struct location *)b;
- if (loc1->count > loc2->count) - return -1; - else - return 1; + return cmp_int(loc2->count, loc1->count); }
static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)