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mm: swap: fix potential buffer overflow in setup_clusters()

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In setup_swap_map(), we only ensure badpages are in range (0, last_page]. 
As maxpages might be < last_page, setup_clusters() will encounter a buffer
overflow when a badpage is >= maxpages.

Only call inc_cluster_info_page() for badpage which is < maxpages to fix
the issue.

Link: https://lkml.kernel.org/r/20250522122554.12209-4-shikemeng@huaweicloud.com
Fixes: b843786b0b ("mm: swapfile: fix SSD detection with swapfile on btrfs")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kemeng Shi
2025-07-24 19:12:34 -07:00
committed by Andrew Morton
parent 255116c5b0
commit 152c1339dc
1 changed files with 7 additions and 3 deletions
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mm/swapfile.c
+7 -3
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@@ -3208,9 +3208,13 @@ static struct swap_cluster_info *setup_clusters(struct swap_info_struct *si,
* and the EOF part of the last cluster.
*/
inc_cluster_info_page(si, cluster_info, 0);
for (i = 0; i < swap_header->info.nr_badpages; i++)
inc_cluster_info_page(si, cluster_info,
swap_header->info.badpages[i]);
for (i = 0; i < swap_header->info.nr_badpages; i++) {
unsigned int page_nr = swap_header->info.badpages[i];
if (page_nr >= maxpages)
continue;
inc_cluster_info_page(si, cluster_info, page_nr);
}
for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
inc_cluster_info_page(si, cluster_info, i);