linux-ext4 - [PATCH 7/7] libext2fs: check for invalid blocks in ext2fs_punch

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Message-Id: <20220607042444.1798015-8-tytso@mit.edu>
Date:   Tue,  7 Jun 2022 00:24:44 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:     Nils Bars <nils.bars@....de>,
        Moritz Schlögel <moritz.schloegel@....de>,
        Nico Schiller <nico.schiller@....de>,
        "Theodore Ts'o" <tytso@....edu>
Subject: [PATCH 7/7] libext2fs: check for invalid blocks in ext2fs_punch_blocks()

If the extent tree has out-of-range physical block numbers, don't try
to release them.

Also add a similar check in ext2fs_block_alloc_stats2() to avoid a
NULL pointer dereference.

Reported-by: Nils Bars <nils.bars@....de>
Reported-by: Moritz Schlögel <moritz.schloegel@....de>
Reported-by: Nico Schiller <nico.schiller@....de>
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
 lib/ext2fs/alloc_stats.c | 3 ++-
 lib/ext2fs/punch.c       | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/ext2fs/alloc_stats.c b/lib/ext2fs/alloc_stats.c
index 3949f618..6f98bcc7 100644
--- a/lib/ext2fs/alloc_stats.c
+++ b/lib/ext2fs/alloc_stats.c
@@ -62,7 +62,8 @@ void ext2fs_block_alloc_stats2(ext2_filsys fs, blk64_t blk, int inuse)
 {
 	int	group = ext2fs_group_of_blk2(fs, blk);
 
-	if (blk >= ext2fs_blocks_count(fs->super)) {
+	if (blk < fs->super->s_first_data_block ||
+	    blk >= ext2fs_blocks_count(fs->super)) {
 #ifndef OMIT_COM_ERR
 		com_err("ext2fs_block_alloc_stats", 0,
 			"Illegal block number: %lu", (unsigned long) blk);
diff --git a/lib/ext2fs/punch.c b/lib/ext2fs/punch.c
index effa1e2d..e2543e1e 100644
--- a/lib/ext2fs/punch.c
+++ b/lib/ext2fs/punch.c
@@ -200,6 +200,10 @@ static errcode_t punch_extent_blocks(ext2_filsys fs, ext2_ino_t ino,
 	__u32		cluster_freed;
 	errcode_t	retval = 0;
 
+	if (free_start < fs->super->s_first_data_block ||
+	    (free_start + free_count) >= ext2fs_blocks_count(fs->super))
+		return EXT2_ET_BAD_BLOCK_NUM;
+
 	/* No bigalloc?  Just free each block. */
 	if (EXT2FS_CLUSTER_RATIO(fs) == 1) {
 		*freed += free_count;
-- 
2.31.0