Squashfs: add additional inode sanity checking

Patch series "Squashfs: performance improvement and a sanity check".

This patchset adds an additional sanity check when reading regular file
inodes, and adds support for SEEK_DATA/SEEK_HOLE lseek() whence values.


This patch (of 2):

Add an additional sanity check when reading regular file inodes.

A regular file if the file size is an exact multiple of the filesystem
block size cannot have a fragment.  This is because by definition a
fragment block stores tailends which are not a whole block in size.

Link: https://lkml.kernel.org/r/20250923220652.568416-1-phillip@squashfs.org.uk
Link: https://lkml.kernel.org/r/20250923220652.568416-2-phillip@squashfs.org.uk
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: plougher

fs/squashfs/inode.c

@@ -144,8 +144,17 @@ int squashfs_read_inode(struct inode *inode, long long ino)
 		if (err < 0)
 			goto failed_read;
 
+		inode->i_size = le32_to_cpu(sqsh_ino->file_size);
 		frag = le32_to_cpu(sqsh_ino->fragment);
 		if (frag != SQUASHFS_INVALID_FRAG) {
+			/*
+			 * the file cannot have a fragment (tailend) and have a
+			 * file size a multiple of the block size
+			 */
+			if ((inode->i_size & (msblk->block_size - 1)) == 0) {
+				err = -EINVAL;
+				goto failed_read;
+			}
 			frag_offset = le32_to_cpu(sqsh_ino->offset);
 			frag_size = squashfs_frag_lookup(sb, frag, &frag_blk);
 			if (frag_size < 0) {
@@ -159,7 +168,6 @@ int squashfs_read_inode(struct inode *inode, long long ino)
 		}
 
 		set_nlink(inode, 1);
-		inode->i_size = le32_to_cpu(sqsh_ino->file_size);
 		inode->i_fop = &generic_ro_fops;
 		inode->i_mode |= S_IFREG;
 		inode->i_blocks = ((inode->i_size - 1) >> 9) + 1;
@@ -188,8 +196,17 @@ int squashfs_read_inode(struct inode *inode, long long ino)
 		if (err < 0)
 			goto failed_read;
 
+		inode->i_size = le64_to_cpu(sqsh_ino->file_size);
 		frag = le32_to_cpu(sqsh_ino->fragment);
 		if (frag != SQUASHFS_INVALID_FRAG) {
+			/*
+			 * the file cannot have a fragment (tailend) and have a
+			 * file size a multiple of the block size
+			 */
+			if ((inode->i_size & (msblk->block_size - 1)) == 0) {
+				err = -EINVAL;
+				goto failed_read;
+			}
 			frag_offset = le32_to_cpu(sqsh_ino->offset);
 			frag_size = squashfs_frag_lookup(sb, frag, &frag_blk);
 			if (frag_size < 0) {
@@ -204,7 +221,6 @@ int squashfs_read_inode(struct inode *inode, long long ino)
 
 		xattr_id = le32_to_cpu(sqsh_ino->xattr);
 		set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
-		inode->i_size = le64_to_cpu(sqsh_ino->file_size);
 		inode->i_op = &squashfs_inode_ops;
 		inode->i_fop = &generic_ro_fops;
 		inode->i_mode |= S_IFREG;