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.

[phillip@squashfs.org.uk: only need to check 64 bit quantity]
Link: https://lkml.kernel.org/r/20250926222305.110103-1-phillip@squashfs.org.uk
Link: https://lkml.kernel.org/r/20250926215935.107233-1-phillip@squashfs.org.uk
Fixes: 6545b246a2c8 ("Squashfs: inode operations")
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reported-by: syzbot+f754e01116421e9754b9@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68d580e5.a00a0220.303701.0019.GAE@google.com/
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/squashfs/inode.c b/fs/squashfs/inode.c
index ddc65d0060633cec7290b24dafd9c80295d7219d..cceae3b78698c3cd1d412ceff6d48aa7e0059b83 100644 (file)
--- a/fs/squashfs/inode.c
+++ b/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) {
                        /*