xfs: use null daddr for unset first bad log block

xlog_do_recovery_pass() may return before setting first_bad.  The caller
must distinguish that case from an error at a valid log block, including
block zero after the log wraps.

Initialize first_bad to XFS_BUF_DADDR_NULL and test it explicitly before
treating the error as a torn write.

Fixes: 7088c4136fa1 ("xfs: detect and trim torn writes during log recovery")
Suggested-by: Darrick J. Wong <djwong@kernel.org>
Reported-by: syzbot+b7dfbed0c6c2b5e9fd34@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b7dfbed0c6c2b5e9fd34
Cc: stable@vger.kernel.org # v4.5
Signed-off-by: Yousef Alhouseen <alhouseenyousef@gmail.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 09e6678ca4878e21b4e76c0d7ffb56c6e8122258..5f984bf5698a89ede88d62c0cd1a240c07572332 100644 (file)
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -1028,7 +1028,7 @@ xlog_verify_head(
 {
        struct xlog_rec_header  *tmp_rhead;
        char                    *tmp_buffer;
-       xfs_daddr_t             first_bad;
+       xfs_daddr_t             first_bad = XFS_BUF_DADDR_NULL;
        xfs_daddr_t             tmp_rhead_blk;
        int                     found;
        int                     error;
@@ -1057,7 +1057,8 @@ xlog_verify_head(
         */
        error = xlog_do_recovery_pass(log, *head_blk, tmp_rhead_blk,
                                      XLOG_RECOVER_CRCPASS, &first_bad);
-       if ((error == -EFSBADCRC || error == -EFSCORRUPTED) && first_bad) {
+       if ((error == -EFSBADCRC || error == -EFSCORRUPTED) &&
+           first_bad != XFS_BUF_DADDR_NULL) {
                /*
                 * We've hit a potential torn write. Reset the error and warn
                 * about it.
@@ -3575,4 +3576,3 @@ xlog_recover_cancel(
        if (xlog_recovery_needed(log))
                xlog_recover_cancel_intents(log);
 }
-