Squashfs: reject negative file sizes in squashfs_read_inode()

Syskaller reports a "WARNING in ovl_copy_up_file" in overlayfs.

This warning is ultimately caused because the underlying Squashfs file
system returns a file with a negative file size.

This commit checks for a negative file size and returns EINVAL.

[[email protected]: only need to check 64 bit quantity]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Fixes: 6545b24 ("Squashfs: inode operations")
Signed-off-by: Phillip Lougher <[email protected]>
Reported-by: [email protected]
Closes: https://lore.kernel.org/all/[email protected]/
Cc: Amir Goldstein <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: plougher

fs/squashfs/inode.c

@@ -197,6 +197,10 @@ int squashfs_read_inode(struct inode *inode, long long ino)
 			goto failed_read;
 
 		inode->i_size = le64_to_cpu(sqsh_ino->file_size);
+		if (inode->i_size < 0) {
+			err = -EINVAL;
+			goto failed_read;
+		}
 		frag = le32_to_cpu(sqsh_ino->fragment);
 		if (frag != SQUASHFS_INVALID_FRAG) {
 			/*