[PATCH V5] squashfs: Add i_size check in squash_read_inode

[Lizhi Xu <lizhi.xu@windriver.com>]

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. Strictly, the check only applies to the
symlink type. Add larger symlink check.

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

diff --git a/fs/squashfs/inode.c b/fs/squashfs/inode.c
index 16bd693d0b3a..6c5dd225482f 100644
--- a/fs/squashfs/inode.c
+++ b/fs/squashfs/inode.c
@@ -287,6 +287,11 @@ int squashfs_read_inode(struct inode *inode, long long ino)
 		inode->i_mode |= S_IFLNK;
 		squashfs_i(inode)->start = block;
 		squashfs_i(inode)->offset = offset;
+		if ((int)inode->i_size < 0 || inode->i_size > PAGE_SIZE) {
+			ERROR("Wrong i_size %d!\n", inode->i_size);
+			return -EINVAL;
+		}
+
 
 		if (type == SQUASHFS_LSYMLINK_TYPE) {
 			__le32 xattr;
-- 
2.43.0