6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Duoming Zhou duoming@zju.edu.cn
[ Upstream commit 483bc08181827fc475643272ffb69c533007e546 ]
When the sco connection is established and then, the sco socket is releasing, timeout_work will be scheduled to judge whether the sco disconnection is timeout. The sock will be deallocated later, but it is dereferenced again in sco_sock_timeout. As a result, the use-after-free bugs will happen. The root cause is shown below:
Cleanup Thread | Worker Thread sco_sock_release | sco_sock_close | __sco_sock_close | sco_sock_set_timer | schedule_delayed_work | sco_sock_kill | (wait a time) sock_put(sk) //FREE | sco_sock_timeout | sock_hold(sk) //USE
The KASAN report triggered by POC is shown below:
[ 95.890016] ================================================================== [ 95.890496] BUG: KASAN: slab-use-after-free in sco_sock_timeout+0x5e/0x1c0 [ 95.890755] Write of size 4 at addr ffff88800c388080 by task kworker/0:0/7 ... [ 95.890755] Workqueue: events sco_sock_timeout [ 95.890755] Call Trace: [ 95.890755] <TASK> [ 95.890755] dump_stack_lvl+0x45/0x110 [ 95.890755] print_address_description+0x78/0x390 [ 95.890755] print_report+0x11b/0x250 [ 95.890755] ? __virt_addr_valid+0xbe/0xf0 [ 95.890755] ? sco_sock_timeout+0x5e/0x1c0 [ 95.890755] kasan_report+0x139/0x170 [ 95.890755] ? update_load_avg+0xe5/0x9f0 [ 95.890755] ? sco_sock_timeout+0x5e/0x1c0 [ 95.890755] kasan_check_range+0x2c3/0x2e0 [ 95.890755] sco_sock_timeout+0x5e/0x1c0 [ 95.890755] process_one_work+0x561/0xc50 [ 95.890755] worker_thread+0xab2/0x13c0 [ 95.890755] ? pr_cont_work+0x490/0x490 [ 95.890755] kthread+0x279/0x300 [ 95.890755] ? pr_cont_work+0x490/0x490 [ 95.890755] ? kthread_blkcg+0xa0/0xa0 [ 95.890755] ret_from_fork+0x34/0x60 [ 95.890755] ? kthread_blkcg+0xa0/0xa0 [ 95.890755] ret_from_fork_asm+0x11/0x20 [ 95.890755] </TASK> [ 95.890755] [ 95.890755] Allocated by task 506: [ 95.890755] kasan_save_track+0x3f/0x70 [ 95.890755] __kasan_kmalloc+0x86/0x90 [ 95.890755] __kmalloc+0x17f/0x360 [ 95.890755] sk_prot_alloc+0xe1/0x1a0 [ 95.890755] sk_alloc+0x31/0x4e0 [ 95.890755] bt_sock_alloc+0x2b/0x2a0 [ 95.890755] sco_sock_create+0xad/0x320 [ 95.890755] bt_sock_create+0x145/0x320 [ 95.890755] __sock_create+0x2e1/0x650 [ 95.890755] __sys_socket+0xd0/0x280 [ 95.890755] __x64_sys_socket+0x75/0x80 [ 95.890755] do_syscall_64+0xc4/0x1b0 [ 95.890755] entry_SYSCALL_64_after_hwframe+0x67/0x6f [ 95.890755] [ 95.890755] Freed by task 506: [ 95.890755] kasan_save_track+0x3f/0x70 [ 95.890755] kasan_save_free_info+0x40/0x50 [ 95.890755] poison_slab_object+0x118/0x180 [ 95.890755] __kasan_slab_free+0x12/0x30 [ 95.890755] kfree+0xb2/0x240 [ 95.890755] __sk_destruct+0x317/0x410 [ 95.890755] sco_sock_release+0x232/0x280 [ 95.890755] sock_close+0xb2/0x210 [ 95.890755] __fput+0x37f/0x770 [ 95.890755] task_work_run+0x1ae/0x210 [ 95.890755] get_signal+0xe17/0xf70 [ 95.890755] arch_do_signal_or_restart+0x3f/0x520 [ 95.890755] syscall_exit_to_user_mode+0x55/0x120 [ 95.890755] do_syscall_64+0xd1/0x1b0 [ 95.890755] entry_SYSCALL_64_after_hwframe+0x67/0x6f [ 95.890755] [ 95.890755] The buggy address belongs to the object at ffff88800c388000 [ 95.890755] which belongs to the cache kmalloc-1k of size 1024 [ 95.890755] The buggy address is located 128 bytes inside of [ 95.890755] freed 1024-byte region [ffff88800c388000, ffff88800c388400) [ 95.890755] [ 95.890755] The buggy address belongs to the physical page: [ 95.890755] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88800c38a800 pfn:0xc388 [ 95.890755] head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0 [ 95.890755] anon flags: 0x100000000000840(slab|head|node=0|zone=1) [ 95.890755] page_type: 0xffffffff() [ 95.890755] raw: 0100000000000840 ffff888006842dc0 0000000000000000 0000000000000001 [ 95.890755] raw: ffff88800c38a800 000000000010000a 00000001ffffffff 0000000000000000 [ 95.890755] head: 0100000000000840 ffff888006842dc0 0000000000000000 0000000000000001 [ 95.890755] head: ffff88800c38a800 000000000010000a 00000001ffffffff 0000000000000000 [ 95.890755] head: 0100000000000003 ffffea000030e201 ffffea000030e248 00000000ffffffff [ 95.890755] head: 0000000800000000 0000000000000000 00000000ffffffff 0000000000000000 [ 95.890755] page dumped because: kasan: bad access detected [ 95.890755] [ 95.890755] Memory state around the buggy address: [ 95.890755] ffff88800c387f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 95.890755] ffff88800c388000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 95.890755] >ffff88800c388080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 95.890755] ^ [ 95.890755] ffff88800c388100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 95.890755] ffff88800c388180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 95.890755] ==================================================================
Fix this problem by adding a check protected by sco_conn_lock to judget whether the conn->hcon is null. Because the conn->hcon will be set to null, when the sock is releasing.
Fixes: ba316be1b6a0 ("Bluetooth: schedule SCO timeouts with delayed_work") Signed-off-by: Duoming Zhou duoming@zju.edu.cn Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/bluetooth/sco.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c index 4a6bf60f3e7aa..301cf802d32c4 100644 --- a/net/bluetooth/sco.c +++ b/net/bluetooth/sco.c @@ -84,6 +84,10 @@ static void sco_sock_timeout(struct work_struct *work) struct sock *sk;
sco_conn_lock(conn); + if (!conn->hcon) { + sco_conn_unlock(conn); + return; + } sk = conn->sk; if (sk) sock_hold(sk);