Commit 7b97d868 authored by zhangyi (F)'s avatar zhangyi (F) Committed by Theodore Ts'o
Browse files

ext4, jbd2: ensure panic by fix a race between jbd2 abort and ext4 error handlers 



In the ext4 filesystem with errors=panic, if one process is recording
errno in the superblock when invoking jbd2_journal_abort() due to some
error cases, it could be raced by another __ext4_abort() which is
setting the SB_RDONLY flag but missing panic because errno has not been
recorded.

jbd2_journal_commit_transaction()
 jbd2_journal_abort()
  journal->j_flags |= JBD2_ABORT;
  jbd2_journal_update_sb_errno()
                                    | ext4_journal_check_start()
                                    |  __ext4_abort()
                                    |   sb->s_flags |= SB_RDONLY;
                                    |   if (!JBD2_REC_ERR)
                                    |        return;
  journal->j_flags |= JBD2_REC_ERR;

Finally, it will no longer trigger panic because the filesystem has
already been set read-only. Fix this by introduce j_abort_mutex to make
sure journal abort is completed before panic, and remove JBD2_REC_ERR
flag.

Fixes: 4327ba52 ("ext4, jbd2: ensure entering into panic after recording an error in superblock")
Signed-off-by: default avatarzhangyi (F) <yi.zhang@huawei.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200609073540.3810702-1-yi.zhang@huawei.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 88ee9d57

fs/ext4/super.c

+5 −11
Original line number Diff line number Diff line
@@ -522,9 +522,6 @@ static void ext4_handle_error(struct super_block *sb) 
		smp_wmb();

		sb->s_flags |= SB_RDONLY;

	} else if (test_opt(sb, ERRORS_PANIC)) {

		if (EXT4_SB(sb)->s_journal &&

		  !(EXT4_SB(sb)->s_journal->j_flags & JBD2_REC_ERR))

			return;

		panic("EXT4-fs (device %s): panic forced after error\n",

			sb->s_id);

	}
@@ -725,24 +722,21 @@ void __ext4_abort(struct super_block *sb, const char *function, 
	va_end(args);



	if (sb_rdonly(sb) == 0) {

		ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");

		EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FS_ABORTED;

		if (EXT4_SB(sb)->s_journal)

			jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);



		ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");

		/*

		 * Make sure updated value of ->s_mount_flags will be visible

		 * before ->s_flags update

		 */

		smp_wmb();

		sb->s_flags |= SB_RDONLY;

		if (EXT4_SB(sb)->s_journal)

			jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);

	}

	if (test_opt(sb, ERRORS_PANIC) && !system_going_down()) {

		if (EXT4_SB(sb)->s_journal &&

		  !(EXT4_SB(sb)->s_journal->j_flags & JBD2_REC_ERR))

			return;

	if (test_opt(sb, ERRORS_PANIC) && !system_going_down())

		panic("EXT4-fs panic from previous error\n");

}

}



void __ext4_msg(struct super_block *sb,

		const char *prefix, const char *fmt, ...)

fs/jbd2/journal.c

+12 −5
Original line number Diff line number Diff line
@@ -1140,6 +1140,7 @@ static journal_t *journal_init_common(struct block_device *bdev, 
	init_waitqueue_head(&journal->j_wait_commit);

	init_waitqueue_head(&journal->j_wait_updates);

	init_waitqueue_head(&journal->j_wait_reserved);

	mutex_init(&journal->j_abort_mutex);

	mutex_init(&journal->j_barrier);

	mutex_init(&journal->j_checkpoint_mutex);

	spin_lock_init(&journal->j_revoke_lock);
@@ -1402,6 +1403,7 @@ static int jbd2_write_superblock(journal_t *journal, int write_flags) 
		printk(KERN_ERR "JBD2: Error %d detected when updating "

		       "journal superblock for %s.\n", ret,

		       journal->j_devname);

		if (!is_journal_aborted(journal))

			jbd2_journal_abort(journal, ret);

	}
@@ -2153,6 +2155,13 @@ void jbd2_journal_abort(journal_t *journal, int errno) 
{

	transaction_t *transaction;



	/*

	 * Lock the aborting procedure until everything is done, this avoid

	 * races between filesystem's error handling flow (e.g. ext4_abort()),

	 * ensure panic after the error info is written into journal's

	 * superblock.

	 */

	mutex_lock(&journal->j_abort_mutex);

	/*

	 * ESHUTDOWN always takes precedence because a file system check

	 * caused by any other journal abort error is not required after
@@ -2167,6 +2176,7 @@ void jbd2_journal_abort(journal_t *journal, int errno) 
			journal->j_errno = errno;

			jbd2_journal_update_sb_errno(journal);

		}

		mutex_unlock(&journal->j_abort_mutex);

		return;

	}
@@ -2188,10 +2198,7 @@ void jbd2_journal_abort(journal_t *journal, int errno) 
	 * layer could realise that a filesystem check is needed.

	 */

	jbd2_journal_update_sb_errno(journal);



	write_lock(&journal->j_state_lock);

	journal->j_flags |= JBD2_REC_ERR;

	write_unlock(&journal->j_state_lock);

	mutex_unlock(&journal->j_abort_mutex);

}



/**

include/linux/jbd2.h

+5 −1
Original line number Diff line number Diff line
@@ -765,6 +765,11 @@ struct journal_s 
	 */

	int			j_errno;



	/**

	 * @j_abort_mutex: Lock the whole aborting procedure.

	 */

	struct mutex		j_abort_mutex;



	/**

	 * @j_sb_buffer: The first part of the superblock buffer.

	 */
@@ -1247,7 +1252,6 @@ JBD2_FEATURE_INCOMPAT_FUNCS(csum3, CSUM_V3) 
#define JBD2_ABORT_ON_SYNCDATA_ERR	0x040	/* Abort the journal on file

						 * data write error in ordered

						 * mode */

#define JBD2_REC_ERR	0x080	/* The errno in the sb has been recorded */



/*

 * Function declarations for the journaling transaction and buffer

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