Illumos #4089 NULL pointer dereference in arc_read()

4089 NULL pointer dereference in arc_read()

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Approved by: Dan McDonald <danmcd@nexenta.com>

References:
  https://www.illumos.org/issues/4089
  illumos/illumos-gate@57815f6b95a743697e148327725b7f568e75e6ea

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2171
Issue #2165
Closes #2198

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 59e6c5bc8b3720519d742994767481cc06d6ec61..00d26592d738a7f11f1b5be520700bbb8e125b11 100644 (file)
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -20,9 +20,9 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
  */
 
 /*
@@ -3268,6 +3268,8 @@ top:
                vdev_t *vd = NULL;
                uint64_t addr = 0;
                boolean_t devw = B_FALSE;
+               enum zio_compress b_compress = ZIO_COMPRESS_OFF;
+               uint64_t b_asize = 0;
 
                if (hdr == NULL) {
                        /* this block is not in the cache */
@@ -3337,10 +3339,12 @@ top:
                hdr->b_acb = acb;
                hdr->b_flags |= ARC_IO_IN_PROGRESS;
 
-               if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
+               if (hdr->b_l2hdr != NULL &&
                    (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
                        devw = hdr->b_l2hdr->b_dev->l2ad_writing;
                        addr = hdr->b_l2hdr->b_daddr;
+                       b_compress = hdr->b_l2hdr->b_compress;
+                       b_asize = hdr->b_l2hdr->b_asize;
                        /*
                         * Lock out device removal.
                         */
@@ -3389,7 +3393,7 @@ top:
                                cb->l2rcb_bp = *bp;
                                cb->l2rcb_zb = *zb;
                                cb->l2rcb_flags = zio_flags;
-                               cb->l2rcb_compress = hdr->b_l2hdr->b_compress;
+                               cb->l2rcb_compress = b_compress;
 
                                ASSERT(addr >= VDEV_LABEL_START_SIZE &&
                                    addr + size < vd->vdev_psize -
@@ -3401,8 +3405,7 @@ top:
                                 * Issue a null zio if the underlying buffer
                                 * was squashed to zero size by compression.
                                 */
-                               if (hdr->b_l2hdr->b_compress ==
-                                   ZIO_COMPRESS_EMPTY) {
+                               if (b_compress == ZIO_COMPRESS_EMPTY) {
                                        rzio = zio_null(pio, spa, vd,
                                            l2arc_read_done, cb,
                                            zio_flags | ZIO_FLAG_DONT_CACHE |
@@ -3411,8 +3414,8 @@ top:
                                            ZIO_FLAG_DONT_RETRY);
                                } else {
                                        rzio = zio_read_phys(pio, vd, addr,
-                                           hdr->b_l2hdr->b_asize,
-                                           buf->b_data, ZIO_CHECKSUM_OFF,
+                                           b_asize, buf->b_data,
+                                           ZIO_CHECKSUM_OFF,
                                            l2arc_read_done, cb, priority,
                                            zio_flags | ZIO_FLAG_DONT_CACHE |
                                            ZIO_FLAG_CANFAIL |
@@ -3421,8 +3424,7 @@ top:
                                }
                                DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
                                    zio_t *, rzio);
-                               ARCSTAT_INCR(arcstat_l2_read_bytes,
-                                   hdr->b_l2hdr->b_asize);
+                               ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize);
 
                                if (*arc_flags & ARC_NOWAIT) {
                                        zio_nowait(rzio);