[PATCH 13/18] libext2fs: Don't cache inodes that fail checksum verification

["Darrick J. Wong" <darrick.wong@oracle.com>]

If an inode fails checksum verification, don't stuff a copy of it in
the inode cache, because this can cause the library to fail to return
the "corrupt inode" error code.

In general, this happens if ext2fs_read_inode_full() is called twice
on an inode with an incorrect checksum.  If fs->flags has
EXT2_FLAG_IGNORE_CSUM_ERRORS set during the first call and *unset*
during the second call, the cache hit during the second call fails to
return EXT2_ET_INODE_CSUM_INVALID as you'd expect.  This happens
during fsck if strict_csums is not set, because the first read_inode
call happens as part of check_blocks and the second call happens
during inode checksum revalidation.  A file system with a slightly
corrupt non-extent inode will trigger this.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 lib/ext2fs/inode.c                      |   12 +++++++-----
 tests/f_no_cache_corrupt_inode/expect.1 |   12 ++++++++++++
 tests/f_no_cache_corrupt_inode/expect.2 |    7 +++++++
 tests/f_no_cache_corrupt_inode/image.gz |  Bin
 tests/f_no_cache_corrupt_inode/name     |    1 +
 5 files changed, 27 insertions(+), 5 deletions(-)
 create mode 100644 tests/f_no_cache_corrupt_inode/expect.1
 create mode 100644 tests/f_no_cache_corrupt_inode/expect.2
 create mode 100644 tests/f_no_cache_corrupt_inode/image.gz
 create mode 100644 tests/f_no_cache_corrupt_inode/name


diff --git a/lib/ext2fs/inode.c b/lib/ext2fs/inode.c
index ca97ab8..9cad5c1 100644
--- a/lib/ext2fs/inode.c
+++ b/lib/ext2fs/inode.c
@@ -580,7 +580,7 @@ errcode_t ext2fs_read_inode_full(ext2_filsys fs, ext2_ino_t ino,
 	io_channel	io;
 	int		length = EXT2_INODE_SIZE(fs->super);
 	struct ext2_inode_large	*iptr;
-	int		cache_slot;
+	int		cache_slot, fail_csum;
 
 	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 
@@ -658,8 +658,8 @@ errcode_t ext2fs_read_inode_full(ext2_filsys fs, ext2_ino_t ino,
 	length = EXT2_INODE_SIZE(fs->super);
 
 	/* Verify the inode checksum. */
-	if (!(fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
-	    !ext2fs_inode_csum_verify(fs, ino, iptr))
+	fail_csum = !ext2fs_inode_csum_verify(fs, ino, iptr);
+	if (!(fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) && fail_csum)
 		return EXT2_ET_INODE_CSUM_INVALID;
 
 #ifdef WORDS_BIGENDIAN
@@ -669,8 +669,10 @@ errcode_t ext2fs_read_inode_full(ext2_filsys fs, ext2_ino_t ino,
 #endif
 
 	/* Update the inode cache bookkeeping */
-	fs->icache->cache_last = cache_slot;
-	fs->icache->cache[cache_slot].ino = ino;
+	if (!fail_csum) {
+		fs->icache->cache_last = cache_slot;
+		fs->icache->cache[cache_slot].ino = ino;
+	}
 	memcpy(inode, iptr, (bufsize > length) ? length : bufsize);
 
 	return 0;
diff --git a/tests/f_no_cache_corrupt_inode/expect.1 b/tests/f_no_cache_corrupt_inode/expect.1
new file mode 100644
index 0000000..94b2cae
--- /dev/null
+++ b/tests/f_no_cache_corrupt_inode/expect.1
@@ -0,0 +1,12 @@
+Pass 1: Checking inodes, blocks, and sizes
+Inode 12 checksum does not match inode.  Running sanity checks.
+Inode 12 passes checks, but checksum does not match inode.  Fix? yes
+
+Pass 2: Checking directory structure
+Pass 3: Checking directory connectivity
+Pass 4: Checking reference counts
+Pass 5: Checking group summary information
+
+test_filesys: ***** FILE SYSTEM WAS MODIFIED *****
+test_filesys: 12/128 files (0.0% non-contiguous), 19/512 blocks
+Exit status is 1
diff --git a/tests/f_no_cache_corrupt_inode/expect.2 b/tests/f_no_cache_corrupt_inode/expect.2
new file mode 100644
index 0000000..1b43315
--- /dev/null
+++ b/tests/f_no_cache_corrupt_inode/expect.2
@@ -0,0 +1,7 @@
+Pass 1: Checking inodes, blocks, and sizes
+Pass 2: Checking directory structure
+Pass 3: Checking directory connectivity
+Pass 4: Checking reference counts
+Pass 5: Checking group summary information
+test_filesys: 12/128 files (0.0% non-contiguous), 19/512 blocks
+Exit status is 0
diff --git a/tests/f_no_cache_corrupt_inode/image.gz b/tests/f_no_cache_corrupt_inode/image.gz
new file mode 100644
index 0000000000000000000000000000000000000000..e17e9216deac289cf5c13a33be87b1810640a66d
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diff --git a/tests/f_no_cache_corrupt_inode/name b/tests/f_no_cache_corrupt_inode/name
new file mode 100644
index 0000000..fb213e2
--- /dev/null
+++ b/tests/f_no_cache_corrupt_inode/name
@@ -0,0 +1 @@
+don't cache inodes that fail checksum verification