l2cap_sock_release(sk) frees sk. However, sk's children are still alive
and point to the already free'd sk's address.
To fix this, l2cap_sock_release(sk) also cleans sk's children.
==================================================================
BUG: KASAN: use-after-free in l2cap_sock_ready_cb+0xb7/0x100 net/bluetooth/l2cap_sock.c:1650
Read of size 8 at addr ffff888104617aa8 by task kworker/u3:0/276
CPU: 0 PID: 276 Comm: kworker/u3:0 Not tainted 6.2.0-00001-gef397bd4d5fb-dirty #59
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: hci2 hci_rx_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x72/0x95 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:306 [inline]
print_report+0x175/0x478 mm/kasan/report.c:417
kasan_report+0xb1/0x130 mm/kasan/report.c:517
l2cap_sock_ready_cb+0xb7/0x100 net/bluetooth/l2cap_sock.c:1650
l2cap_chan_ready+0x10e/0x1e0 net/bluetooth/l2cap_core.c:1386
l2cap_config_req+0x753/0x9f0 net/bluetooth/l2cap_core.c:4480
l2cap_bredr_sig_cmd net/bluetooth/l2cap_core.c:5739 [inline]
l2cap_sig_channel net/bluetooth/l2cap_core.c:6509 [inline]
l2cap_recv_frame+0xe2e/0x43c0 net/bluetooth/l2cap_core.c:7788
l2cap_recv_acldata+0x6ed/0x7e0 net/bluetooth/l2cap_core.c:8506
hci_acldata_packet net/bluetooth/hci_core.c:3813 [inline]
hci_rx_work+0x66e/0xbc0 net/bluetooth/hci_core.c:4048
process_one_work+0x4ea/0x8e0 kernel/workqueue.c:2289
worker_thread+0x364/0x8e0 kernel/workqueue.c:2436
kthread+0x1b9/0x200 kernel/kthread.c:376
ret_from_fork+0x2c/0x50 arch/x86/entry/entry_64.S:308
</TASK>
Allocated by task 288:
kasan_save_stack+0x22/0x50 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0x82/0x90 mm/kasan/common.c:383
kasan_kmalloc include/linux/kasan.h:211 [inline]
__do_kmalloc_node mm/slab_common.c:968 [inline]
__kmalloc+0x5a/0x140 mm/slab_common.c:981
kmalloc include/linux/slab.h:584 [inline]
sk_prot_alloc+0x113/0x1f0 net/core/sock.c:2040
sk_alloc+0x36/0x3c0 net/core/sock.c:2093
l2cap_sock_alloc.constprop.0+0x39/0x1c0 net/bluetooth/l2cap_sock.c:1852
l2cap_sock_create+0x10d/0x220 net/bluetooth/l2cap_sock.c:1898
bt_sock_create+0x183/0x290 net/bluetooth/af_bluetooth.c:132
__sock_create+0x226/0x380 net/socket.c:1518
sock_create net/socket.c:1569 [inline]
__sys_socket_create net/socket.c:1606 [inline]
__sys_socket_create net/socket.c:1591 [inline]
__sys_socket+0x112/0x200 net/socket.c:1639
__do_sys_socket net/socket.c:1652 [inline]
__se_sys_socket net/socket.c:1650 [inline]
__x64_sys_socket+0x40/0x50 net/socket.c:1650
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3f/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x72/0xdc
Freed by task 288:
kasan_save_stack+0x22/0x50 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:523
____kasan_slab_free mm/kasan/common.c:236 [inline]
____kasan_slab_free mm/kasan/common.c:200 [inline]
__kasan_slab_free+0x10a/0x190 mm/kasan/common.c:244
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1781 [inline]
slab_free_freelist_hook mm/slub.c:1807 [inline]
slab_free mm/slub.c:3787 [inline]
__kmem_cache_free+0x88/0x1f0 mm/slub.c:3800
sk_prot_free net/core/sock.c:2076 [inline]
__sk_destruct+0x347/0x430 net/core/sock.c:2168
sk_destruct+0x9c/0xb0 net/core/sock.c:2183
__sk_free+0x82/0x220 net/core/sock.c:2194
sk_free+0x7c/0xa0 net/core/sock.c:2205
sock_put include/net/sock.h:1991 [inline]
l2cap_sock_kill+0x256/0x2b0 net/bluetooth/l2cap_sock.c:1257
l2cap_sock_release+0x1a7/0x220 net/bluetooth/l2cap_sock.c:1428
__sock_release+0x80/0x150 net/socket.c:650
sock_close+0x19/0x30 net/socket.c:1368
__fput+0x17a/0x5c0 fs/file_table.c:320
task_work_run+0x132/0x1c0 kernel/task_work.c:179
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x113/0x120 kernel/entry/common.c:203
__syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
syscall_exit_to_user_mode+0x21/0x50 kernel/entry/common.c:296
do_syscall_64+0x4c/0x90 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x72/0xdc
The buggy address belongs to the object at ffff888104617800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 680 bytes inside of
1024-byte region [ffff888104617800, ffff888104617c00)
The buggy address belongs to the physical page:
page:00000000dbca6a80 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888104614000 pfn:0x104614
head:00000000dbca6a80 order:2 compound_mapcount:0 subpages_mapcount:0 compound_pincount:0
flags: 0x200000000010200(slab|head|node=0|zone=2)
raw: 0200000000010200 ffff888100041dc0 ffffea0004212c10 ffffea0004234b10
raw: ffff888104614000 0000000000080002 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888104617980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888104617a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888104617a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888104617b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888104617b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Ack: This bug is found by FuzzBT with a modified Syzkaller. Other
contributors are Ruoyu Wu and Hui Peng.
Signed-off-by: Sungwoo Kim <iam@xxxxxxxxxxxx>
---
Changes in v2:
- Fix a compile error: Add a forward declaration for l2cap_sock_cleanup_listen()
- Lint'ed; Remove trailing tabs
- Link to v1: https://lore.kernel.org/lkml/20230526084038.2199788-1-iam@xxxxxxxxxxxx/
---
net/bluetooth/l2cap_sock.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index eebe25610..947ca580b 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -46,6 +46,7 @@ static const struct proto_ops l2cap_sock_ops;
static void l2cap_sock_init(struct sock *sk, struct sock *parent);
static struct sock *l2cap_sock_alloc(struct net *net, struct socket *sock,
int proto, gfp_t prio, int kern);
+static void l2cap_sock_cleanup_listen(struct sock *parent);
bool l2cap_is_socket(struct socket *sock)
{
@@ -1415,6 +1416,7 @@ static int l2cap_sock_release(struct socket *sock)
if (!sk)
return 0;
+ l2cap_sock_cleanup_listen(sk);
bt_sock_unlink(&l2cap_sk_list, sk);
err = l2cap_sock_shutdown(sock, SHUT_RDWR);
--
2.34.1
