+ squashfs-reject-negative-file-sizes-in-squashfs_read_inode.patch added to mm-nonmm-unstable branch

+ squashfs-reject-negative-file-sizes-in-squashfs_read_inode.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: Squashfs: reject negative file sizes in squashfs_read_inode()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     squashfs-reject-negative-file-sizes-in-squashfs_read_inode.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/squashfs-reject-negative-file-sizes-in-squashfs_read_inode.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Phillip Lougher <phillip@squashfs.org.uk>
Subject: Squashfs: reject negative file sizes in squashfs_read_inode()
Date: Fri, 26 Sep 2025 22:59:35 +0100

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.

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>
---

 fs/squashfs/inode.c |   22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

--- a/fs/squashfs/inode.c~squashfs-reject-negative-file-sizes-in-squashfs_read_inode
+++ a/fs/squashfs/inode.c
@@ -145,6 +145,10 @@ int squashfs_read_inode(struct inode *in
 			goto failed_read;
 
 		inode->i_size = le32_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) {
 			/*
@@ -197,6 +201,10 @@ int squashfs_read_inode(struct inode *in
 			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) {
 			/*
@@ -249,8 +257,12 @@ int squashfs_read_inode(struct inode *in
 		if (err < 0)
 			goto failed_read;
 
-		set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
 		inode->i_size = le16_to_cpu(sqsh_ino->file_size);
+		if (inode->i_size < 0) {
+			err = -EINVAL;
+			goto failed_read;
+		}
+		set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
 		inode->i_op = &squashfs_dir_inode_ops;
 		inode->i_fop = &squashfs_dir_ops;
 		inode->i_mode |= S_IFDIR;
@@ -273,9 +285,13 @@ int squashfs_read_inode(struct inode *in
 		if (err < 0)
 			goto failed_read;
 
+		inode->i_size = le32_to_cpu(sqsh_ino->file_size);
+		if (inode->i_size < 0) {
+			err = -EINVAL;
+			goto failed_read;
+		}
 		xattr_id = le32_to_cpu(sqsh_ino->xattr);
 		set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
-		inode->i_size = le32_to_cpu(sqsh_ino->file_size);
 		inode->i_op = &squashfs_dir_inode_ops;
 		inode->i_fop = &squashfs_dir_ops;
 		inode->i_mode |= S_IFDIR;
@@ -302,7 +318,7 @@ int squashfs_read_inode(struct inode *in
 			goto failed_read;
 
 		inode->i_size = le32_to_cpu(sqsh_ino->symlink_size);
-		if (inode->i_size > PAGE_SIZE) {
+		if (inode->i_size < 0 || inode->i_size > PAGE_SIZE) {
 			ERROR("Corrupted symlink\n");
 			return -EINVAL;
 		}
_

Patches currently in -mm which might be from phillip@squashfs.org.uk are

squashfs-fix-uninit-value-in-squashfs_get_parent.patch
squashfs-add-additional-inode-sanity-checking.patch
squashfs-add-seek_data-seek_hole-support.patch
squashfs-reject-negative-file-sizes-in-squashfs_read_inode.patch