From 164b2c01e30a6e3e64520135e89679c6ec1eaadb Mon Sep 17 00:00:00 2001 From: Alexander Motin Date: Thu, 28 Nov 2019 13:29:00 -0500 Subject: [PATCH] Fix use-after-free in case of L2ARC prefetch failure. In case L2ARC read failed, l2arc_read_done() creates _different_ ZIO to read data from the original storage device. Unfortunately pointer to the failed ZIO remains in hdr->b_l1hdr.b_acb->acb_zio_head, and if some other read try to bump the ZIO priority, it will crash. The problem is reproducible by corrupting L2ARC content and reading some data with prefetch if l2arc_noprefetch tunable is changed to 0. With the default setting the issue is probably not reproducible now. Sponsored-By: iXsystems, Inc. Signed-off-by: Alexander Motin --- module/zfs/arc.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/module/zfs/arc.c b/module/zfs/arc.c index 87df07cc065e..2ca4b6bef5a4 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -7873,7 +7873,6 @@ l2arc_read_done(zio_t *zio) zio->io_private = hdr; arc_read_done(zio); } else { - mutex_exit(hash_lock); /* * Buffer didn't survive caching. Increment stats and * reissue to the original storage device. @@ -7898,10 +7897,24 @@ l2arc_read_done(zio_t *zio) ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); - zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp, + zio = zio_read(pio, zio->io_spa, zio->io_bp, abd, zio->io_size, arc_read_done, hdr, zio->io_priority, cb->l2rcb_flags, - &cb->l2rcb_zb)); + &cb->l2rcb_zb); + + /* + * Original ZIO will be freed, so we need to update + * ARC header with the new ZIO pointer to be used + * by zio_change_priority() in arc_read(). + */ + for (struct arc_callback *acb = hdr->b_l1hdr.b_acb; + acb != NULL; acb = acb->acb_next) + acb->acb_zio_head = zio; + + mutex_exit(hash_lock); + zio_nowait(zio); + } else { + mutex_exit(hash_lock); } }