squashfs: fix memory leak in squashfs_fill_super

jira VULN-79855
cve-bf CVE-2025-38415
commit-author Phillip Lougher <phillip@squashfs.org.uk>
commit b64700d
upstream-diff |
	Replaced errorf with ERROR due to missing 5a2be12
	("vfs: Convert squashfs to use the new mount API") and
	c6b8226 ("vfs: Introduce logging functions") its deps.

If sb_min_blocksize returns 0, squashfs_fill_super exits without freeing
allocated memory (sb->s_fs_info).

Fix this by moving the call to sb_min_blocksize to before memory is
allocated.

Link: https://lkml.kernel.org/r/20250811223740.110392-1-phillip@squashfs.org.uk
Fixes: 734aa85 ("Squashfs: check return result of sb_min_blocksize")
	Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
	Reported-by: Scott GUO <scottzhguo@tencent.com>
Closes: https://lore.kernel.org/all/20250811061921.3807353-1-scott_gzh@163.com
	Cc: <stable@vger.kernel.org>
	Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit b64700d)
	Signed-off-by: Roxana Nicolescu <rnicolescu@ciq.com>

Author: roxanan1996

fs/squashfs/super.c

@@ -84,23 +84,23 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	unsigned short flags;
 	unsigned int fragments;
 	u64 lookup_table_start, xattr_id_table_start, next_table;
-	int err;
+	int err, devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
 
 	TRACE("Entered squashfs_fill_superblock\n");
 
+	if (!devblksize) {
+		ERROR("squashfs: unable to set blocksize\n");
+		return -EINVAL;
+	}
+
 	sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
 	if (sb->s_fs_info == NULL) {
 		ERROR("Failed to allocate squashfs_sb_info\n");
 		return -ENOMEM;
 	}
 	msblk = sb->s_fs_info;
 
-	msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
-	if (!msblk->devblksize) {
-		ERROR("squashfs: unable to set blocksize\n");
-		return -EINVAL;
-	}
-
+	msblk->devblksize = devblksize;
 	msblk->devblksize_log2 = ffz(~msblk->devblksize);
 
 	mutex_init(&msblk->read_data_mutex);