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panic in bpobj_space(): null pointer dereference

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This is a race condition in the deadlist code.

A thread executing an administrative command that uses
dsl_deadlist_space_range() holds the lock of the whole deadlist_t to
protect the access of all its entries that the deadlist contains in an
avl tree.

Sync threads trying to insert a new entry in the deadlist (through
dsl_deadlist_insert() -> dle_enqueue()) do not hold the deadlist lock at
that moment.  If the dle_bpobj is the empty bpobj (our sentinel value),
we close and reopen it.  Between these two operations, it is possible
for the dsl_deadlist_space_range() thread to dereference that bpobj
which is NULL during that window.

Threads should hold the a deadlist's dl_lock when they manipulate its
internal data so scenarios like the one above are avoided.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #5762
This commit is contained in:
Matthew Ahrens
2017-02-09 10:19:12 -08:00
committed by Brian Behlendorf
parent b0eac56a4d
commit df7eeccc75
2 changed files with 25 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files
module/zfs/bpobj.c
+2 -2
View File
@@ -20,7 +20,7 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2011, 2014 by Delphix. All rights reserved.
* Copyright (c) 2011, 2016 by Delphix. All rights reserved.
*/
#include <sys/bpobj.h>
@@ -395,6 +395,7 @@ bpobj_enqueue_subobj(bpobj_t *bpo, uint64_t subobj, dmu_tx_t *tx)
return;
}
mutex_enter(&bpo->bpo_lock);
dmu_buf_will_dirty(bpo->bpo_dbuf, tx);
if (bpo->bpo_phys->bpo_subobjs == 0) {
bpo->bpo_phys->bpo_subobjs = dmu_object_alloc(bpo->bpo_os,
@@ -405,7 +406,6 @@ bpobj_enqueue_subobj(bpobj_t *bpo, uint64_t subobj, dmu_tx_t *tx)
ASSERT0(dmu_object_info(bpo->bpo_os, bpo->bpo_phys->bpo_subobjs, &doi));
ASSERT3U(doi.doi_type, ==, DMU_OT_BPOBJ_SUBOBJ);
mutex_enter(&bpo->bpo_lock);
dmu_write(bpo->bpo_os, bpo->bpo_phys->bpo_subobjs,
bpo->bpo_phys->bpo_num_subobjs * sizeof (subobj),
sizeof (subobj), &subobj, tx);