xfs: fix buffer use after free on IO error

[cascardo/linux.git] / fs / xfs / xfs_buf.c

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 107f2fd..cb10a0a 100644 (file)
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1372,21 +1372,29 @@ xfs_buf_iorequest(
                xfs_buf_wait_unpin(bp);
        xfs_buf_hold(bp);
 
-       /* Set the count to 1 initially, this will stop an I/O
+       /*
+        * Set the count to 1 initially, this will stop an I/O
         * completion callout which happens before we have started
         * all the I/O from calling xfs_buf_ioend too early.
         */
        atomic_set(&bp->b_io_remaining, 1);
        _xfs_buf_ioapply(bp);
-       _xfs_buf_ioend(bp, 1);
+       /*
+        * If _xfs_buf_ioapply failed, we'll get back here with
+        * only the reference we took above.  _xfs_buf_ioend will
+        * drop it to zero, so we'd better not queue it for later,
+        * or we'll free it before it's done.
+        */
+       _xfs_buf_ioend(bp, bp->b_error ? 0 : 1);
 
        xfs_buf_rele(bp);
 }
 
 /*
  * Waits for I/O to complete on the buffer supplied.  It returns immediately if
- * no I/O is pending or there is already a pending error on the buffer.  It
- * returns the I/O error code, if any, or 0 if there was no error.
+ * no I/O is pending or there is already a pending error on the buffer, in which
+ * case nothing will ever complete.  It returns the I/O error code, if any, or
+ * 0 if there was no error.
  */
 int
 xfs_buf_iowait(