From 0225e10972fa809728b8d4c1bd2772b3ec3fdb57 Mon Sep 17 00:00:00 2001 From: Alexei Filippov Date: Sat, 19 Aug 2023 20:32:16 +0300 Subject: [PATCH] jfs: validate max amount of blocks before allocation. The lack of checking bmp->db_max_freebud in extBalloc() can lead to shift out of bounds, so this patch prevents undefined behavior, because bmp->db_max_freebud == -1 only if there is no free space. Signed-off-by: Aleksei Filippov Signed-off-by: Dave Kleikamp Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-and-tested-by: syzbot+5f088f29593e6b4c8db8@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?id=01abadbd6ae6a08b1f1987aa61554c6b3ac19ff2 --- fs/jfs/jfs_extent.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/jfs/jfs_extent.c b/fs/jfs/jfs_extent.c index adaa9ad50d4c..63d21822d309 100644 --- a/fs/jfs/jfs_extent.c +++ b/fs/jfs/jfs_extent.c @@ -311,6 +311,11 @@ extBalloc(struct inode *ip, s64 hint, s64 * nblocks, s64 * blkno) * blocks in the map. in that case, we'll start off with the * maximum free. */ + + /* give up if no space left */ + if (bmp->db_maxfreebud == -1) + return -ENOSPC; + max = (s64) 1 << bmp->db_maxfreebud; if (*nblocks >= max && *nblocks > nbperpage) nb = nblks = (max > nbperpage) ? max : nbperpage;