From: Lihong Kou koulihong@huawei.com
[ Upstream commit f9c70bdc279b191da8d60777c627702c06e4a37d ]
In the case we set or free the global value listen_chan in different threads, we can encounter the UAF problems because the method is not protected by any lock, add one to avoid this bug.
BUG: KASAN: use-after-free in l2cap_chan_close+0x48/0x990 net/bluetooth/l2cap_core.c:730 Read of size 8 at addr ffff888096950000 by task kworker/1:102/2868
CPU: 1 PID: 2868 Comm: kworker/1:102 Not tainted 5.5.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events do_enable_set Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1fb/0x318 lib/dump_stack.c:118 print_address_description+0x74/0x5c0 mm/kasan/report.c:374 __kasan_report+0x149/0x1c0 mm/kasan/report.c:506 kasan_report+0x26/0x50 mm/kasan/common.c:641 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135 l2cap_chan_close+0x48/0x990 net/bluetooth/l2cap_core.c:730 do_enable_set+0x660/0x900 net/bluetooth/6lowpan.c:1074 process_one_work+0x7f5/0x10f0 kernel/workqueue.c:2264 worker_thread+0xbbc/0x1630 kernel/workqueue.c:2410 kthread+0x332/0x350 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Allocated by task 2870: save_stack mm/kasan/common.c:72 [inline] set_track mm/kasan/common.c:80 [inline] __kasan_kmalloc+0x118/0x1c0 mm/kasan/common.c:515 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529 kmem_cache_alloc_trace+0x221/0x2f0 mm/slab.c:3551 kmalloc include/linux/slab.h:555 [inline] kzalloc include/linux/slab.h:669 [inline] l2cap_chan_create+0x50/0x320 net/bluetooth/l2cap_core.c:446 chan_create net/bluetooth/6lowpan.c:640 [inline] bt_6lowpan_listen net/bluetooth/6lowpan.c:959 [inline] do_enable_set+0x6a4/0x900 net/bluetooth/6lowpan.c:1078 process_one_work+0x7f5/0x10f0 kernel/workqueue.c:2264 worker_thread+0xbbc/0x1630 kernel/workqueue.c:2410 kthread+0x332/0x350 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Freed by task 2870: save_stack mm/kasan/common.c:72 [inline] set_track mm/kasan/common.c:80 [inline] kasan_set_free_info mm/kasan/common.c:337 [inline] __kasan_slab_free+0x12e/0x1e0 mm/kasan/common.c:476 kasan_slab_free+0xe/0x10 mm/kasan/common.c:485 __cache_free mm/slab.c:3426 [inline] kfree+0x10d/0x220 mm/slab.c:3757 l2cap_chan_destroy net/bluetooth/l2cap_core.c:484 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x170/0x190 net/bluetooth/l2cap_core.c:498 do_enable_set+0x66c/0x900 net/bluetooth/6lowpan.c:1075 process_one_work+0x7f5/0x10f0 kernel/workqueue.c:2264 worker_thread+0xbbc/0x1630 kernel/workqueue.c:2410 kthread+0x332/0x350 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
The buggy address belongs to the object at ffff888096950000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 0 bytes inside of 2048-byte region [ffff888096950000, ffff888096950800) The buggy address belongs to the page: page:ffffea00025a5400 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0 flags: 0xfffe0000000200(slab) raw: 00fffe0000000200 ffffea00027d1548 ffffea0002397808 ffff8880aa400e00 raw: 0000000000000000 ffff888096950000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff88809694ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88809694ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888096950000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff888096950080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888096950100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
Reported-by: syzbot+96414aa0033c363d8458@syzkaller.appspotmail.com Signed-off-by: Lihong Kou koulihong@huawei.com Signed-off-by: Marcel Holtmann marcel@holtmann.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/bluetooth/6lowpan.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c index 357475cceec61..9a75f9b00b512 100644 --- a/net/bluetooth/6lowpan.c +++ b/net/bluetooth/6lowpan.c @@ -57,6 +57,7 @@ static bool enable_6lowpan; /* We are listening incoming connections via this channel */ static struct l2cap_chan *listen_chan; +static DEFINE_MUTEX(set_lock);
struct lowpan_peer { struct list_head list; @@ -1082,12 +1083,14 @@ static void do_enable_set(struct work_struct *work)
enable_6lowpan = set_enable->flag;
+ mutex_lock(&set_lock); if (listen_chan) { l2cap_chan_close(listen_chan, 0); l2cap_chan_put(listen_chan); }
listen_chan = bt_6lowpan_listen(); + mutex_unlock(&set_lock);
kfree(set_enable); } @@ -1139,11 +1142,13 @@ static ssize_t lowpan_control_write(struct file *fp, if (ret == -EINVAL) return ret;
+ mutex_lock(&set_lock); if (listen_chan) { l2cap_chan_close(listen_chan, 0); l2cap_chan_put(listen_chan); listen_chan = NULL; } + mutex_unlock(&set_lock);
if (conn) { struct lowpan_peer *peer;