From 00561c65abf81bbebc66c767c1de0821b2bb51b0 Mon Sep 17 00:00:00 2001 From: Phillip Lougher Date: Tue, 25 May 2021 15:30:55 +0000 Subject: [PATCH] squashfs: fix divide error in calculate_skip() stable inclusion from stable-5.10.38 commit 2ed1d90162a0c0683ecbe0c4802187fa22d641c3 bugzilla: 51875 CVE: NA -------------------------------- commit d6e621de1fceb3b098ebf435ef7ea91ec4838a1a upstream. Sysbot has reported a "divide error" which has been identified as being caused by a corrupted file_size value within the file inode. This value has been corrupted to a much larger value than expected. Calculate_skip() is passed i_size_read(inode) >> msblk->block_log. Due to the file_size value corruption this overflows the int argument/variable in that function, leading to the divide error. This patch changes the function to use u64. This will accommodate any unexpectedly large values due to corruption. The value returned from calculate_skip() is clamped to be never more than SQUASHFS_CACHED_BLKS - 1, or 7. So file_size corruption does not lead to an unexpectedly large return result here. Link: https://lkml.kernel.org/r/20210507152618.9447-1-phillip@squashfs.org.uk Signed-off-by: Phillip Lougher Reported-by: Reported-by: Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman Signed-off-by: Chen Jun Acked-by: Weilong Chen Signed-off-by: Zheng Zengkai --- fs/squashfs/file.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c index 7b1128398976..89d492916dea 100644 --- a/fs/squashfs/file.c +++ b/fs/squashfs/file.c @@ -211,11 +211,11 @@ static long long read_indexes(struct super_block *sb, int n, * If the skip factor is limited in this way then the file will use multiple * slots. */ -static inline int calculate_skip(int blocks) +static inline int calculate_skip(u64 blocks) { - int skip = blocks / ((SQUASHFS_META_ENTRIES + 1) + u64 skip = blocks / ((SQUASHFS_META_ENTRIES + 1) * SQUASHFS_META_INDEXES); - return min(SQUASHFS_CACHED_BLKS - 1, skip + 1); + return min((u64) SQUASHFS_CACHED_BLKS - 1, skip + 1); } -- GitLab