Commit bac8dca9 authored Nov 28, 2008 by Christoph Hellwig Committed by Niv Sardi Dec 01, 2008

[XFS] fix NULL pointer dereference in xfs_log_force_umount



xfs_log_force_umount may be called very early during log recovery where

If we fail a buffer read in xlog_recover_do_inode_trans we abort the mount.
But at that point log recovery has started delayed writeback of inode
buffers.   As part of the aborted mount we try to flush out all delwri
buffers, but at that point we have already freed the superblock, and set
mp->m_sb_bp to NULL, and xfs_log_force_umount which gets called after
the inode buffer writeback trips over it.

Make xfs_log_force_umount a little more careful when accessing mp->m_sb_bp
to avoid this.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Niv Sardi <xaiki@sgi.com>

parent b5a20aa2

fs/xfs/xfs_log.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -3569,6 +3569,7 @@ xfs_log_force_umount(
		if (!log \|\|
		log->l_flags & XLOG_ACTIVE_RECOVERY) {
		mp->m_flags \|= XFS_MOUNT_FS_SHUTDOWN;
		if (mp->m_sb_bp)
		XFS_BUF_DONE(mp->m_sb_bp);
		return 0;
		}
		@@ -3590,7 +3591,9 @@ xfs_log_force_umount(
		spin_lock(&log->l_icloglock);
		spin_lock(&log->l_grant_lock);
		mp->m_flags \|= XFS_MOUNT_FS_SHUTDOWN;
		if (mp->m_sb_bp)
		XFS_BUF_DONE(mp->m_sb_bp);

		/*
		* This flag is sort of redundant because of the mount flag, but
		* it's good to maintain the separation between the log and the rest

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