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Date: Mon, 1 Oct 2018 22:49:17 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Thomas Graf <tgraf@...g.ch>,
Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH v2 net] inet: frags: rework rhashtable dismantle
syszbot found an interesting use-after-free [1] happening
while IPv4 fragment rhashtable was destroyed at netns dismantle.
While no insertions can possibly happen at the time a dismantling
netns is destroying this rhashtable, timers can still fire and
attempt to remove elements from this rhashtable.
This is forbidden, since rhashtable_free_and_destroy() has
no synchronization against concurrent inserts and deletes.
Add a new nf->dead flag so that timers do not attempt
a rhashtable_remove_fast() operation.
[1]
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:188 [inline]
BUG: KASAN: use-after-free in rhashtable_last_table+0x216/0x240 lib/rhashtable.c:217
Read of size 8 at addr ffff88019a4c8840 by task kworker/0:4/8279
CPU: 0 PID: 8279 Comm: kworker/0:4 Not tainted 4.19.0-rc5+ #61
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events rht_deferred_worker
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
__read_once_size include/linux/compiler.h:188 [inline]
rhashtable_last_table+0x216/0x240 lib/rhashtable.c:217
rht_deferred_worker+0x157/0x1de0 lib/rhashtable.c:410
process_one_work+0xc90/0x1b90 kernel/workqueue.c:2153
worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
Allocated by task 5:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
__do_kmalloc_node mm/slab.c:3682 [inline]
__kmalloc_node+0x47/0x70 mm/slab.c:3689
kmalloc_node include/linux/slab.h:555 [inline]
kvmalloc_node+0xb9/0xf0 mm/util.c:423
kvmalloc include/linux/mm.h:577 [inline]
kvzalloc include/linux/mm.h:585 [inline]
bucket_table_alloc+0x9a/0x4e0 lib/rhashtable.c:176
rhashtable_rehash_alloc+0x73/0x100 lib/rhashtable.c:353
rht_deferred_worker+0x278/0x1de0 lib/rhashtable.c:413
process_one_work+0xc90/0x1b90 kernel/workqueue.c:2153
worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
Freed by task 8283:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3813
kvfree+0x61/0x70 mm/util.c:452
bucket_table_free+0xda/0x250 lib/rhashtable.c:108
rhashtable_free_and_destroy+0x152/0x900 lib/rhashtable.c:1163
inet_frags_exit_net+0x3d/0x50 net/ipv4/inet_fragment.c:96
ipv4_frags_exit_net+0x73/0x90 net/ipv4/ip_fragment.c:914
ops_exit_list.isra.7+0xb0/0x160 net/core/net_namespace.c:153
cleanup_net+0x555/0xb10 net/core/net_namespace.c:551
process_one_work+0xc90/0x1b90 kernel/workqueue.c:2153
worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
The buggy address belongs to the object at ffff88019a4c8800
which belongs to the cache kmalloc-16384 of size 16384
The buggy address is located 64 bytes inside of
16384-byte region [ffff88019a4c8800, ffff88019a4cc800)
The buggy address belongs to the page:
page:ffffea0006693200 count:1 mapcount:0 mapping:ffff8801da802200 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffffea0006685608 ffffea0006617c08 ffff8801da802200
raw: 0000000000000000 ffff88019a4c8800 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88019a4c8700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88019a4c8780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88019a4c8800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88019a4c8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88019a4c8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
Fixes: 648700f76b03 ("inet: frags: use rhashtables for reassembly units")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
Cc: Thomas Graf <tgraf@...g.ch>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
---
include/net/inet_frag.h | 4 +++-
net/ipv4/inet_fragment.c | 31 +++++++++++++++++++++----------
2 files changed, 24 insertions(+), 11 deletions(-)
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index 1662cbc0b46b45296a367ecbdaf03c68854fdce7..ffe5e1be40212fa63e360f3e29a56c1b2ce897ee 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -11,7 +11,7 @@ struct netns_frags {
int timeout;
int max_dist;
struct inet_frags *f;
-
+ bool dead;
struct rhashtable rhashtable ____cacheline_aligned_in_smp;
/* Keep atomic mem on separate cachelines in structs that include it */
@@ -24,11 +24,13 @@ struct netns_frags {
* @INET_FRAG_FIRST_IN: first fragment has arrived
* @INET_FRAG_LAST_IN: final fragment has arrived
* @INET_FRAG_COMPLETE: frag queue has been processed and is due for destruction
+ * @INET_FRAG_HASH_DEAD: inet_frag_kill() has not removed fq from rhashtable
*/
enum {
INET_FRAG_FIRST_IN = BIT(0),
INET_FRAG_LAST_IN = BIT(1),
INET_FRAG_COMPLETE = BIT(2),
+ INET_FRAG_HASH_DEAD = BIT(3),
};
struct frag_v4_compare_key {
diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c
index bcb11f3a27c0c34115af05034a5a20f57842eb0a..887134425350cc7c8ee081d8c83a037074d96d93 100644
--- a/net/ipv4/inet_fragment.c
+++ b/net/ipv4/inet_fragment.c
@@ -71,28 +71,31 @@ EXPORT_SYMBOL(inet_frags_fini);
static void inet_frags_free_cb(void *ptr, void *arg)
{
struct inet_frag_queue *fq = ptr;
+ int count = 0;
- /* If we can not cancel the timer, it means this frag_queue
- * is already disappearing, we have nothing to do.
- * Otherwise, we own a refcount until the end of this function.
- */
- if (!del_timer(&fq->timer))
- return;
+ if (del_timer_sync(&fq->timer))
+ count++;
spin_lock_bh(&fq->lock);
if (!(fq->flags & INET_FRAG_COMPLETE)) {
fq->flags |= INET_FRAG_COMPLETE;
- refcount_dec(&fq->refcnt);
+ count++;
+ } else if (fq->flags & INET_FRAG_HASH_DEAD) {
+ count++;
}
spin_unlock_bh(&fq->lock);
- inet_frag_put(fq);
+ if (refcount_sub_and_test(count, &fq->refcnt))
+ inet_frag_destroy(fq);
}
void inet_frags_exit_net(struct netns_frags *nf)
{
nf->high_thresh = 0; /* prevent creation of new frags */
+ /* paired with READ_ONCE() in inet_frag_kill() */
+ smp_store_release(&nf->dead, true);
+
rhashtable_free_and_destroy(&nf->rhashtable, inet_frags_free_cb, NULL);
}
EXPORT_SYMBOL(inet_frags_exit_net);
@@ -106,8 +109,16 @@ void inet_frag_kill(struct inet_frag_queue *fq)
struct netns_frags *nf = fq->net;
fq->flags |= INET_FRAG_COMPLETE;
- rhashtable_remove_fast(&nf->rhashtable, &fq->node, nf->f->rhash_params);
- refcount_dec(&fq->refcnt);
+ /* This READ_ONCE() is paired with smp_store_release()
+ * in inet_frags_exit_net().
+ */
+ if (!READ_ONCE(nf->dead)) {
+ rhashtable_remove_fast(&nf->rhashtable, &fq->node,
+ nf->f->rhash_params);
+ refcount_dec(&fq->refcnt);
+ } else {
+ fq->flags |= INET_FRAG_HASH_DEAD;
+ }
}
}
EXPORT_SYMBOL(inet_frag_kill);
--
2.19.0.605.g01d371f741-goog
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