general protection fault in hci_chan_del

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b3298500 Merge tag 'for-5.10/dm-fixes' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=144f0bf7500000
kernel config: https://syzkaller.appspot.com/x/.config?x=e49433cfed49b7d9
dashboard link: https://syzkaller.appspot.com/bug?extid=4c574753a325a601326c
compiler: gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4c5747...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000b00: 0000 [#1] PREEMPT SMP KASAN
KASAN: probably user-memory-access in range [0x0000000000005800-0x0000000000005807]
CPU: 1 PID: 30846 Comm: syz-executor.1 Not tainted 5.10.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__list_del_entry_valid+0x81/0xf0 lib/list_debug.c:51
Code: 0f 84 d3 c0 fb 04 48 b8 22 01 00 00 00 00 ad de 49 39 c4 0f 84 d4 c0 fb 04 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 75 51 49 8b 14 24 48 39 ea 0f 85 8b c0 fb 04 49 8d 7d
RSP: 0018:ffffc9001653fb50 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000054 RCX: ffffc9000aab6000
RDX: 0000000000000b00 RSI: ffffffff87df1892 RDI: ffff888014569f08
RBP: ffff888014569f00 R08: 0000000000000001 R09: ffff88801a734a77
R10: ffffed10034e694e R11: 0000000000000001 R12: 0000000000005800
R13: 3000004010000000 R14: fffffbfff19608c8 R15: 0000000000000067
FS: 00007f7eae8b2700(0000) GS:ffff8880b9f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055c3b4ac8030 CR3: 0000000025fa7000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__list_del_entry include/linux/list.h:132 [inline]
list_del_rcu include/linux/rculist.h:166 [inline]
hci_chan_del+0x4e/0x200 net/bluetooth/hci_conn.c:1733
l2cap_conn_del+0x478/0x7b0 net/bluetooth/l2cap_core.c:1900
l2cap_disconn_cfm net/bluetooth/l2cap_core.c:8161 [inline]
l2cap_disconn_cfm+0x98/0xd0 net/bluetooth/l2cap_core.c:8154
hci_disconn_cfm include/net/bluetooth/hci_core.h:1441 [inline]
hci_conn_hash_flush+0x127/0x260 net/bluetooth/hci_conn.c:1557
hci_dev_do_close+0x569/0x1110 net/bluetooth/hci_core.c:1770
hci_rfkill_set_block+0x19c/0x1d0 net/bluetooth/hci_core.c:2209
rfkill_set_block+0x1f9/0x540 net/rfkill/core.c:341
rfkill_fop_write+0x267/0x500 net/rfkill/core.c:1240
vfs_write+0x28e/0xa30 fs/read_write.c:603
ksys_write+0x1ee/0x250 fs/read_write.c:658
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45de79
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f7eae8b1c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045de79
RDX: 0000000000000008 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 000000000169fb7f R14: 00007f7eae8b29c0 R15: 000000000118bf2c
Modules linked in:
---[ end trace 8aa7b596113f27d8 ]---
RIP: 0010:__list_del_entry_valid+0x81/0xf0 lib/list_debug.c:51
Code: 0f 84 d3 c0 fb 04 48 b8 22 01 00 00 00 00 ad de 49 39 c4 0f 84 d4 c0 fb 04 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 75 51 49 8b 14 24 48 39 ea 0f 85 8b c0 fb 04 49 8d 7d
RSP: 0018:ffffc9001653fb50 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000054 RCX: ffffc9000aab6000
RDX: 0000000000000b00 RSI: ffffffff87df1892 RDI: ffff888014569f08
RBP: ffff888014569f00 R08: 0000000000000001 R09: ffff88801a734a77
R10: ffffed10034e694e R11: 0000000000000001 R12: 0000000000005800
R13: 3000004010000000 R14: fffffbfff19608c8 R15: 0000000000000067
FS: 00007f7eae8b2700(0000) GS:ffff8880b9f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001590004 CR3: 0000000025fa7000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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[Hillf Danton]

Mon, 07 Dec 2020 23:41:11 -0800

Looks like a race in between disconn_cfm and connet_cfm.

--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1855,6 +1855,7 @@ static void l2cap_conn_del(struct hci_co
{
struct l2cap_conn *conn = hcon->l2cap_data;
struct l2cap_chan *chan, *l;
+ struct hci_chan *hchan;

if (!conn)
return;
@@ -1880,8 +1881,18 @@ static void l2cap_conn_del(struct hci_co
/* Force the connection to be immediately dropped */
hcon->disc_timeout = 0;

+ if (conn->hchan == NULL)
+ return;
+
mutex_lock(&conn->chan_lock);

+ if (conn->hchan == NULL) {
+ mutex_unlock(&conn->chan_lock);
+ return;
+ }
+ hchan = conn->hchan;
+ conn->hchan = NULL;
+
/* Kill channels */
list_for_each_entry_safe(chan, l, &conn->chan_l, list) {
l2cap_chan_hold(chan);
@@ -1897,13 +1908,12 @@ static void l2cap_conn_del(struct hci_co

mutex_unlock(&conn->chan_lock);

- hci_chan_del(conn->hchan);
+ hci_chan_del(hchan);

if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT)
cancel_delayed_work_sync(&conn->info_timer);

hcon->l2cap_data = NULL;
- conn->hchan = NULL;
l2cap_conn_put(conn);
}

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.