[PATCH V3] squashfs: Add i_size check in squash_read_inode

[Lizhi Xu]

syzbot report KMSAN: uninit-value in pick_link, the root cause is that
squashfs_symlink_read_folio did not check the length, resulting in folio
not being initialized and did not return the corresponding error code.

The length is calculated from i_size, so it is necessary to add a check
when i_size is initialized to confirm that its value is correct, otherwise
an error -EINVAL will be returned.

Reported-and-tested-by: syzbot+24ac24ff58dc5b0d26b9@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=24ac24ff58dc5b0d26b9
Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
---
 fs/squashfs/inode.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/squashfs/inode.c b/fs/squashfs/inode.c
index 16bd693d0b3a..3c667939f1d7 100644
--- a/fs/squashfs/inode.c
+++ b/fs/squashfs/inode.c
@@ -394,6 +394,11 @@ int squashfs_read_inode(struct inode *inode, long long ino)
 		return -EINVAL;
 	}
 
+	if ((int)inode->i_size < 0) {
+		ERROR("Wrong i_size %d!\n", inode->i_size);
+		return -EINVAL;
+	}
+
 	if (xattr_id != SQUASHFS_INVALID_XATTR && msblk->xattr_id_table) {
 		err = squashfs_xattr_lookup(sb, xattr_id,
 					&squashfs_i(inode)->xattr_count,
-- 
2.43.0