From: Namjae Jeon <linkinjeon@kernel.org>
To: sj1557.seo@samsung.com, yuezhang.mo@sony.com
Cc: linux-fsdevel@vger.kernel.org,
Namjae Jeon <linkinjeon@kernel.org>,
Jiaming Zhang <r772577952@gmail.com>
Subject: [PATCH] exfat: fix divide-by-zero in exfat_allocate_bitmap
Date: Tue, 18 Nov 2025 11:48:04 +0900 [thread overview]
Message-ID: <20251118024804.7143-1-linkinjeon@kernel.org> (raw)
The variable max_ra_count can be 0 in exfat_allocate_bitmap(),
which causes a divide-by-zero error in the subsequent modulo operation
(i % max_ra_count), leading to a system crash.
When max_ra_count is 0, it means that readahead is not used. This patch
load the bitmap without readahead.
Reported-by: Jiaming Zhang <r772577952@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
fs/exfat/balloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c
index b387bf7df65e..5429041c7eaf 100644
--- a/fs/exfat/balloc.c
+++ b/fs/exfat/balloc.c
@@ -106,7 +106,7 @@ static int exfat_allocate_bitmap(struct super_block *sb,
(PAGE_SHIFT - sb->s_blocksize_bits);
for (i = 0; i < sbi->map_sectors; i++) {
/* Trigger the next readahead in advance. */
- if (0 == (i % max_ra_count)) {
+ if (max_ra_count && 0 == (i % max_ra_count)) {
blk_start_plug(&plug);
for (j = i; j < min(max_ra_count, sbi->map_sectors - i) + i; j++)
sb_breadahead(sb, sector + j);
--
2.25.1
reply other threads:[~2025-11-18 2:48 UTC|newest]
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