linux-kernel - [PATCH 2/2] ext4: fix a bug accessing freed memory in ext4

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Message-ID: <49056FA5.7070202@hitachi.com>
Date:	Mon, 27 Oct 2008 16:37:09 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	Theodore Tso <tytso@....edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Vegard Nossum <vegard.nossum@...il.com>, Jan Kara <jack@....cz>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Al Viro <viro@...iv.linux.org.uk>, linux-ext4@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Ingo Molnar <mingo@...e.hu>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	sugita <yumiko.sugita.yf@...achi.com>,
	Satoshi OSHIMA <satoshi.oshima.fk@...achi.com>
Subject: [PATCH 2/2] ext4: fix a bug accessing freed memory in ext4_abort

Vegard Nossum reported a bug which accesses freed memory.  When
journal has been aborted, ext4_put_super() calls ext4_abort() after
freeing the journal_t object, and then ext4_abort() accesses it.
This patch fix it.

Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
---
 fs/ext4/super.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

Index: linux-2.6.28-rc2/fs/ext4/super.c
===================================================================
--- linux-2.6.28-rc2.orig/fs/ext4/super.c
+++ linux-2.6.28-rc2/fs/ext4/super.c
@@ -333,7 +333,8 @@ void ext4_abort(struct super_block *sb, 
 	EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
 	sb->s_flags |= MS_RDONLY;
 	EXT4_SB(sb)->s_mount_opt |= EXT4_MOUNT_ABORT;
-	jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);
+	if (EXT4_SB(sb)->s_journal)
+		jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);
 }
 
 void ext4_warning(struct super_block *sb, const char *function,
@@ -442,14 +443,16 @@ static void ext4_put_super(struct super_
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct ext4_super_block *es = sbi->s_es;
-	int i;
+	int i, err;
 
 	ext4_mb_release(sb);
 	ext4_ext_release(sb);
 	ext4_xattr_put_super(sb);
-	if (jbd2_journal_destroy(sbi->s_journal) < 0)
-		ext4_abort(sb, __func__, "Couldn't clean up the journal");
+	err = jbd2_journal_destroy(sbi->s_journal);
 	sbi->s_journal = NULL;
+	if (err < 0)
+		ext4_abort(sb, __func__, "Couldn't clean up the journal");
+
 	if (!(sb->s_flags & MS_RDONLY)) {
 		EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
 		es->s_state = cpu_to_le16(sbi->s_mount_state);


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