xfs: fix _xfs_buf_find oops on blocks beyond the filesystem end
authorDave Chinner <dchinner@redhat.com>
Mon, 21 Jan 2013 12:53:52 +0000 (23:53 +1100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 4 Feb 2013 00:27:06 +0000 (18:27 -0600)
commita56040731e5b00081c6d6c26b99e6e257a5d63d7
tree16f56433da0dda11341c77984f85b7eae54a097a
parentd7603fd9328805a5e8ebe66d870e2a1210fde6f4
xfs: fix _xfs_buf_find oops on blocks beyond the filesystem end

commit eb178619f930fa2ba2348de332a1ff1c66a31424 upstream.

When _xfs_buf_find is passed an out of range address, it will fail
to find a relevant struct xfs_perag and oops with a null
dereference. This can happen when trying to walk a filesystem with a
metadata inode that has a partially corrupted extent map (i.e. the
block number returned is corrupt, but is otherwise intact) and we
try to read from the corrupted block address.

In this case, just fail the lookup. If it is readahead being issued,
it will simply not be done, but if it is real read that fails we
will get an error being reported.  Ideally this case should result
in an EFSCORRUPTED error being reported, but we cannot return an
error through xfs_buf_read() or xfs_buf_get() so this lookup failure
may result in ENOMEM or EIO errors being reported instead.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
Cc: CAI Qian <caiqian@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/xfs/xfs_buf.c