linux-kernel - [ 83/83] ext4: fix metadata checksum calculation for the superblock

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Date:	Wed, 21 Nov 2012 16:42:45 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, George Spelvin <linux@...izon.com>,
	"Theodore Tso" <tytso@....edu>
Subject: [ 83/83] ext4: fix metadata checksum calculation for the superblock

3.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Theodore Ts'o <tytso@....edu>

commit 06db49e68ae70cf16819b85a14057acb2820776a upstream.

The function ext4_handle_dirty_super() was calculating the superblock
on the wrong block data.  As a result, when the superblock is modified
while it is mounted (most commonly, when inodes are added or removed
from the orphan list), the superblock checksum would be wrong.  We
didn't notice because the superblock *was* being correctly calculated
in ext4_commit_super(), and this would get called when the file system
was unmounted.  So the problem only became obvious if the system
crashed while the file system was mounted.

Fix this by removing the poorly designed function signature for
ext4_superblock_csum_set(); if it only took a single argument, the
pointer to a struct superblock, the ambiguity which caused this
mistake would have been impossible.

Reported-by: George Spelvin <linux@...izon.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Tested-by: George Spelvin <linux@...izon.com>

---
 fs/ext4/ext4.h      |    3 +--
 fs/ext4/ext4_jbd2.c |    8 ++------
 fs/ext4/resize.c    |    2 +-
 fs/ext4/super.c     |    7 ++++---
 4 files changed, 8 insertions(+), 12 deletions(-)

--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2046,8 +2046,7 @@ extern int ext4_resize_fs(struct super_b
 extern int ext4_calculate_overhead(struct super_block *sb);
 extern int ext4_superblock_csum_verify(struct super_block *sb,
 				       struct ext4_super_block *es);
-extern void ext4_superblock_csum_set(struct super_block *sb,
-				     struct ext4_super_block *es);
+extern void ext4_superblock_csum_set(struct super_block *sb);
 extern void *ext4_kvmalloc(size_t size, gfp_t flags);
 extern void *ext4_kvzalloc(size_t size, gfp_t flags);
 extern void ext4_kvfree(void *ptr);
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -143,17 +143,13 @@ int __ext4_handle_dirty_super(const char
 	struct buffer_head *bh = EXT4_SB(sb)->s_sbh;
 	int err = 0;
 
+	ext4_superblock_csum_set(sb);
 	if (ext4_handle_valid(handle)) {
-		ext4_superblock_csum_set(sb,
-				(struct ext4_super_block *)bh->b_data);
 		err = jbd2_journal_dirty_metadata(handle, bh);
 		if (err)
 			ext4_journal_abort_handle(where, line, __func__,
 						  bh, handle, err);
-	} else {
-		ext4_superblock_csum_set(sb,
-				(struct ext4_super_block *)bh->b_data);
+	} else
 		mark_buffer_dirty(bh);
-	}
 	return err;
 }
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -979,7 +979,7 @@ static void update_backups(struct super_
 		goto exit_err;
 	}
 
-	ext4_superblock_csum_set(sb, (struct ext4_super_block *)data);
+	ext4_superblock_csum_set(sb);
 
 	while ((group = ext4_list_backups(sb, &three, &five, &seven)) < last) {
 		struct buffer_head *bh;
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -143,9 +143,10 @@ int ext4_superblock_csum_verify(struct s
 	return es->s_checksum == ext4_superblock_csum(sb, es);
 }
 
-void ext4_superblock_csum_set(struct super_block *sb,
-			      struct ext4_super_block *es)
+void ext4_superblock_csum_set(struct super_block *sb)
 {
+	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
+
 	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
 		EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
 		return;
@@ -4343,7 +4344,7 @@ static int ext4_commit_super(struct supe
 		cpu_to_le32(percpu_counter_sum_positive(
 				&EXT4_SB(sb)->s_freeinodes_counter));
 	BUFFER_TRACE(sbh, "marking dirty");
-	ext4_superblock_csum_set(sb, es);
+	ext4_superblock_csum_set(sb);
 	mark_buffer_dirty(sbh);
 	if (sync) {
 		error = sync_dirty_buffer(sbh);


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