[PATCH 6.12.y 2/2] Squashfs: reject negative file sizes in squashfs_read_inode()

[Sasha Levin <sashal@kernel.org>]

From: Phillip Lougher <phillip@squashfs.org.uk>

[ Upstream commit 9f1c14c1de1bdde395f6cc893efa4f80a2ae3b2b ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/squashfs/inode.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/squashfs/inode.c b/fs/squashfs/inode.c
index 77eec1772998b..de8657a77703a 100644
--- a/fs/squashfs/inode.c
+++ b/fs/squashfs/inode.c
@@ -192,6 +192,10 @@ 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) {
 			/*
-- 
2.51.0