From d70a5804c563b5e34825353ba9927509df709651 Mon Sep 17 00:00:00 2001 From: Namjae Jeon Date: Tue, 18 Nov 2025 11:10:26 +0900 Subject: [PATCH] exfat: fix divide-by-zero in exfat_allocate_bitmap 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. Fixes: 9fd688678dd8 ("exfat: optimize allocation bitmap loading time") Reported-by: Jiaming Zhang Signed-off-by: Namjae Jeon --- 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);