[CVE-2016-10200,SRU,Trusty] l2tp: fix racy SOCK_ZAPPED flag check in l2tp_ip{, 6}_bind()

Message ID 20170828081014.24028-1-po-hsu.lin@canonical.com
State New
Headers show
Series
  • [CVE-2016-10200,SRU,Trusty] l2tp: fix racy SOCK_ZAPPED flag check in l2tp_ip{, 6}_bind()
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Commit Message

Po-Hsu Lin Aug. 28, 2017, 8:10 a.m.
From: Guillaume Nault <g.nault@alphalink.fr>

CVE-2016-10200

Lock socket before checking the SOCK_ZAPPED flag in l2tp_ip6_bind().
Without lock, a concurrent call could modify the socket flags between
the sock_flag(sk, SOCK_ZAPPED) test and the lock_sock() call. This way,
a socket could be inserted twice in l2tp_ip6_bind_table. Releasing it
would then leave a stale pointer there, generating use-after-free
errors when walking through the list or modifying adjacent entries.

BUG: KASAN: use-after-free in l2tp_ip6_close+0x22e/0x290 at addr ffff8800081b0ed8
Write of size 8 by task syz-executor/10987
CPU: 0 PID: 10987 Comm: syz-executor Not tainted 4.8.0+ #39
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
 ffff880031d97838 ffffffff829f835b ffff88001b5a1640 ffff8800081b0ec0
 ffff8800081b15a0 ffff8800081b6d20 ffff880031d97860 ffffffff8174d3cc
 ffff880031d978f0 ffff8800081b0e80 ffff88001b5a1640 ffff880031d978e0
Call Trace:
 [<ffffffff829f835b>] dump_stack+0xb3/0x118 lib/dump_stack.c:15
 [<ffffffff8174d3cc>] kasan_object_err+0x1c/0x70 mm/kasan/report.c:156
 [<     inline     >] print_address_description mm/kasan/report.c:194
 [<ffffffff8174d666>] kasan_report_error+0x1f6/0x4d0 mm/kasan/report.c:283
 [<     inline     >] kasan_report mm/kasan/report.c:303
 [<ffffffff8174db7e>] __asan_report_store8_noabort+0x3e/0x40 mm/kasan/report.c:329
 [<     inline     >] __write_once_size ./include/linux/compiler.h:249
 [<     inline     >] __hlist_del ./include/linux/list.h:622
 [<     inline     >] hlist_del_init ./include/linux/list.h:637
 [<ffffffff8579047e>] l2tp_ip6_close+0x22e/0x290 net/l2tp/l2tp_ip6.c:239
 [<ffffffff850b2dfd>] inet_release+0xed/0x1c0 net/ipv4/af_inet.c:415
 [<ffffffff851dc5a0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:422
 [<ffffffff84c4581d>] sock_release+0x8d/0x1d0 net/socket.c:570
 [<ffffffff84c45976>] sock_close+0x16/0x20 net/socket.c:1017
 [<ffffffff817a108c>] __fput+0x28c/0x780 fs/file_table.c:208
 [<ffffffff817a1605>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff813774f9>] task_work_run+0xf9/0x170
 [<ffffffff81324aae>] do_exit+0x85e/0x2a00
 [<ffffffff81326dc8>] do_group_exit+0x108/0x330
 [<ffffffff81348cf7>] get_signal+0x617/0x17a0 kernel/signal.c:2307
 [<ffffffff811b49af>] do_signal+0x7f/0x18f0
 [<ffffffff810039bf>] exit_to_usermode_loop+0xbf/0x150 arch/x86/entry/common.c:156
 [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
 [<ffffffff81006060>] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259
 [<ffffffff85e4d726>] entry_SYSCALL_64_fastpath+0xc4/0xc6
Object at ffff8800081b0ec0, in cache L2TP/IPv6 size: 1448
Allocated:
PID = 10987
 [ 1116.897025] [<ffffffff811ddcb6>] save_stack_trace+0x16/0x20
 [ 1116.897025] [<ffffffff8174c736>] save_stack+0x46/0xd0
 [ 1116.897025] [<ffffffff8174c9ad>] kasan_kmalloc+0xad/0xe0
 [ 1116.897025] [<ffffffff8174cee2>] kasan_slab_alloc+0x12/0x20
 [ 1116.897025] [<     inline     >] slab_post_alloc_hook mm/slab.h:417
 [ 1116.897025] [<     inline     >] slab_alloc_node mm/slub.c:2708
 [ 1116.897025] [<     inline     >] slab_alloc mm/slub.c:2716
 [ 1116.897025] [<ffffffff817476a8>] kmem_cache_alloc+0xc8/0x2b0 mm/slub.c:2721
 [ 1116.897025] [<ffffffff84c4f6a9>] sk_prot_alloc+0x69/0x2b0 net/core/sock.c:1326
 [ 1116.897025] [<ffffffff84c58ac8>] sk_alloc+0x38/0xae0 net/core/sock.c:1388
 [ 1116.897025] [<ffffffff851ddf67>] inet6_create+0x2d7/0x1000 net/ipv6/af_inet6.c:182
 [ 1116.897025] [<ffffffff84c4af7b>] __sock_create+0x37b/0x640 net/socket.c:1153
 [ 1116.897025] [<     inline     >] sock_create net/socket.c:1193
 [ 1116.897025] [<     inline     >] SYSC_socket net/socket.c:1223
 [ 1116.897025] [<ffffffff84c4b46f>] SyS_socket+0xef/0x1b0 net/socket.c:1203
 [ 1116.897025] [<ffffffff85e4d685>] entry_SYSCALL_64_fastpath+0x23/0xc6
Freed:
PID = 10987
 [ 1116.897025] [<ffffffff811ddcb6>] save_stack_trace+0x16/0x20
 [ 1116.897025] [<ffffffff8174c736>] save_stack+0x46/0xd0
 [ 1116.897025] [<ffffffff8174cf61>] kasan_slab_free+0x71/0xb0
 [ 1116.897025] [<     inline     >] slab_free_hook mm/slub.c:1352
 [ 1116.897025] [<     inline     >] slab_free_freelist_hook mm/slub.c:1374
 [ 1116.897025] [<     inline     >] slab_free mm/slub.c:2951
 [ 1116.897025] [<ffffffff81748b28>] kmem_cache_free+0xc8/0x330 mm/slub.c:2973
 [ 1116.897025] [<     inline     >] sk_prot_free net/core/sock.c:1369
 [ 1116.897025] [<ffffffff84c541eb>] __sk_destruct+0x32b/0x4f0 net/core/sock.c:1444
 [ 1116.897025] [<ffffffff84c5aca4>] sk_destruct+0x44/0x80 net/core/sock.c:1452
 [ 1116.897025] [<ffffffff84c5ad33>] __sk_free+0x53/0x220 net/core/sock.c:1460
 [ 1116.897025] [<ffffffff84c5af23>] sk_free+0x23/0x30 net/core/sock.c:1471
 [ 1116.897025] [<ffffffff84c5cb6c>] sk_common_release+0x28c/0x3e0 ./include/net/sock.h:1589
 [ 1116.897025] [<ffffffff8579044e>] l2tp_ip6_close+0x1fe/0x290 net/l2tp/l2tp_ip6.c:243
 [ 1116.897025] [<ffffffff850b2dfd>] inet_release+0xed/0x1c0 net/ipv4/af_inet.c:415
 [ 1116.897025] [<ffffffff851dc5a0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:422
 [ 1116.897025] [<ffffffff84c4581d>] sock_release+0x8d/0x1d0 net/socket.c:570
 [ 1116.897025] [<ffffffff84c45976>] sock_close+0x16/0x20 net/socket.c:1017
 [ 1116.897025] [<ffffffff817a108c>] __fput+0x28c/0x780 fs/file_table.c:208
 [ 1116.897025] [<ffffffff817a1605>] ____fput+0x15/0x20 fs/file_table.c:244
 [ 1116.897025] [<ffffffff813774f9>] task_work_run+0xf9/0x170
 [ 1116.897025] [<ffffffff81324aae>] do_exit+0x85e/0x2a00
 [ 1116.897025] [<ffffffff81326dc8>] do_group_exit+0x108/0x330
 [ 1116.897025] [<ffffffff81348cf7>] get_signal+0x617/0x17a0 kernel/signal.c:2307
 [ 1116.897025] [<ffffffff811b49af>] do_signal+0x7f/0x18f0
 [ 1116.897025] [<ffffffff810039bf>] exit_to_usermode_loop+0xbf/0x150 arch/x86/entry/common.c:156
 [ 1116.897025] [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
 [ 1116.897025] [<ffffffff81006060>] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259
 [ 1116.897025] [<ffffffff85e4d726>] entry_SYSCALL_64_fastpath+0xc4/0xc6
Memory state around the buggy address:
 ffff8800081b0d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8800081b0e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8800081b0e80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                    ^
 ffff8800081b0f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8800081b0f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Comments

Kleber Sacilotto de Souza Aug. 28, 2017, 10:27 a.m. | #1
On 08/28/17 10:10, Po-Hsu Lin wrote:
> From: Guillaume Nault <g.nault@alphalink.fr>
> 
> CVE-2016-10200
> 
> Lock socket before checking the SOCK_ZAPPED flag in l2tp_ip6_bind().
> Without lock, a concurrent call could modify the socket flags between
> the sock_flag(sk, SOCK_ZAPPED) test and the lock_sock() call. This way,
> a socket could be inserted twice in l2tp_ip6_bind_table. Releasing it
> would then leave a stale pointer there, generating use-after-free
> errors when walking through the list or modifying adjacent entries.
> 
> BUG: KASAN: use-after-free in l2tp_ip6_close+0x22e/0x290 at addr ffff8800081b0ed8
> Write of size 8 by task syz-executor/10987
> CPU: 0 PID: 10987 Comm: syz-executor Not tainted 4.8.0+ #39
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
>  ffff880031d97838 ffffffff829f835b ffff88001b5a1640 ffff8800081b0ec0
>  ffff8800081b15a0 ffff8800081b6d20 ffff880031d97860 ffffffff8174d3cc
>  ffff880031d978f0 ffff8800081b0e80 ffff88001b5a1640 ffff880031d978e0
> Call Trace:
>  [<ffffffff829f835b>] dump_stack+0xb3/0x118 lib/dump_stack.c:15
>  [<ffffffff8174d3cc>] kasan_object_err+0x1c/0x70 mm/kasan/report.c:156
>  [<     inline     >] print_address_description mm/kasan/report.c:194
>  [<ffffffff8174d666>] kasan_report_error+0x1f6/0x4d0 mm/kasan/report.c:283
>  [<     inline     >] kasan_report mm/kasan/report.c:303
>  [<ffffffff8174db7e>] __asan_report_store8_noabort+0x3e/0x40 mm/kasan/report.c:329
>  [<     inline     >] __write_once_size ./include/linux/compiler.h:249
>  [<     inline     >] __hlist_del ./include/linux/list.h:622
>  [<     inline     >] hlist_del_init ./include/linux/list.h:637
>  [<ffffffff8579047e>] l2tp_ip6_close+0x22e/0x290 net/l2tp/l2tp_ip6.c:239
>  [<ffffffff850b2dfd>] inet_release+0xed/0x1c0 net/ipv4/af_inet.c:415
>  [<ffffffff851dc5a0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:422
>  [<ffffffff84c4581d>] sock_release+0x8d/0x1d0 net/socket.c:570
>  [<ffffffff84c45976>] sock_close+0x16/0x20 net/socket.c:1017
>  [<ffffffff817a108c>] __fput+0x28c/0x780 fs/file_table.c:208
>  [<ffffffff817a1605>] ____fput+0x15/0x20 fs/file_table.c:244
>  [<ffffffff813774f9>] task_work_run+0xf9/0x170
>  [<ffffffff81324aae>] do_exit+0x85e/0x2a00
>  [<ffffffff81326dc8>] do_group_exit+0x108/0x330
>  [<ffffffff81348cf7>] get_signal+0x617/0x17a0 kernel/signal.c:2307
>  [<ffffffff811b49af>] do_signal+0x7f/0x18f0
>  [<ffffffff810039bf>] exit_to_usermode_loop+0xbf/0x150 arch/x86/entry/common.c:156
>  [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
>  [<ffffffff81006060>] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259
>  [<ffffffff85e4d726>] entry_SYSCALL_64_fastpath+0xc4/0xc6
> Object at ffff8800081b0ec0, in cache L2TP/IPv6 size: 1448
> Allocated:
> PID = 10987
>  [ 1116.897025] [<ffffffff811ddcb6>] save_stack_trace+0x16/0x20
>  [ 1116.897025] [<ffffffff8174c736>] save_stack+0x46/0xd0
>  [ 1116.897025] [<ffffffff8174c9ad>] kasan_kmalloc+0xad/0xe0
>  [ 1116.897025] [<ffffffff8174cee2>] kasan_slab_alloc+0x12/0x20
>  [ 1116.897025] [<     inline     >] slab_post_alloc_hook mm/slab.h:417
>  [ 1116.897025] [<     inline     >] slab_alloc_node mm/slub.c:2708
>  [ 1116.897025] [<     inline     >] slab_alloc mm/slub.c:2716
>  [ 1116.897025] [<ffffffff817476a8>] kmem_cache_alloc+0xc8/0x2b0 mm/slub.c:2721
>  [ 1116.897025] [<ffffffff84c4f6a9>] sk_prot_alloc+0x69/0x2b0 net/core/sock.c:1326
>  [ 1116.897025] [<ffffffff84c58ac8>] sk_alloc+0x38/0xae0 net/core/sock.c:1388
>  [ 1116.897025] [<ffffffff851ddf67>] inet6_create+0x2d7/0x1000 net/ipv6/af_inet6.c:182
>  [ 1116.897025] [<ffffffff84c4af7b>] __sock_create+0x37b/0x640 net/socket.c:1153
>  [ 1116.897025] [<     inline     >] sock_create net/socket.c:1193
>  [ 1116.897025] [<     inline     >] SYSC_socket net/socket.c:1223
>  [ 1116.897025] [<ffffffff84c4b46f>] SyS_socket+0xef/0x1b0 net/socket.c:1203
>  [ 1116.897025] [<ffffffff85e4d685>] entry_SYSCALL_64_fastpath+0x23/0xc6
> Freed:
> PID = 10987
>  [ 1116.897025] [<ffffffff811ddcb6>] save_stack_trace+0x16/0x20
>  [ 1116.897025] [<ffffffff8174c736>] save_stack+0x46/0xd0
>  [ 1116.897025] [<ffffffff8174cf61>] kasan_slab_free+0x71/0xb0
>  [ 1116.897025] [<     inline     >] slab_free_hook mm/slub.c:1352
>  [ 1116.897025] [<     inline     >] slab_free_freelist_hook mm/slub.c:1374
>  [ 1116.897025] [<     inline     >] slab_free mm/slub.c:2951
>  [ 1116.897025] [<ffffffff81748b28>] kmem_cache_free+0xc8/0x330 mm/slub.c:2973
>  [ 1116.897025] [<     inline     >] sk_prot_free net/core/sock.c:1369
>  [ 1116.897025] [<ffffffff84c541eb>] __sk_destruct+0x32b/0x4f0 net/core/sock.c:1444
>  [ 1116.897025] [<ffffffff84c5aca4>] sk_destruct+0x44/0x80 net/core/sock.c:1452
>  [ 1116.897025] [<ffffffff84c5ad33>] __sk_free+0x53/0x220 net/core/sock.c:1460
>  [ 1116.897025] [<ffffffff84c5af23>] sk_free+0x23/0x30 net/core/sock.c:1471
>  [ 1116.897025] [<ffffffff84c5cb6c>] sk_common_release+0x28c/0x3e0 ./include/net/sock.h:1589
>  [ 1116.897025] [<ffffffff8579044e>] l2tp_ip6_close+0x1fe/0x290 net/l2tp/l2tp_ip6.c:243
>  [ 1116.897025] [<ffffffff850b2dfd>] inet_release+0xed/0x1c0 net/ipv4/af_inet.c:415
>  [ 1116.897025] [<ffffffff851dc5a0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:422
>  [ 1116.897025] [<ffffffff84c4581d>] sock_release+0x8d/0x1d0 net/socket.c:570
>  [ 1116.897025] [<ffffffff84c45976>] sock_close+0x16/0x20 net/socket.c:1017
>  [ 1116.897025] [<ffffffff817a108c>] __fput+0x28c/0x780 fs/file_table.c:208
>  [ 1116.897025] [<ffffffff817a1605>] ____fput+0x15/0x20 fs/file_table.c:244
>  [ 1116.897025] [<ffffffff813774f9>] task_work_run+0xf9/0x170
>  [ 1116.897025] [<ffffffff81324aae>] do_exit+0x85e/0x2a00
>  [ 1116.897025] [<ffffffff81326dc8>] do_group_exit+0x108/0x330
>  [ 1116.897025] [<ffffffff81348cf7>] get_signal+0x617/0x17a0 kernel/signal.c:2307
>  [ 1116.897025] [<ffffffff811b49af>] do_signal+0x7f/0x18f0
>  [ 1116.897025] [<ffffffff810039bf>] exit_to_usermode_loop+0xbf/0x150 arch/x86/entry/common.c:156
>  [ 1116.897025] [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
>  [ 1116.897025] [<ffffffff81006060>] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259
>  [ 1116.897025] [<ffffffff85e4d726>] entry_SYSCALL_64_fastpath+0xc4/0xc6
> Memory state around the buggy address:
>  ffff8800081b0d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8800081b0e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> ffff8800081b0e80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>                                                     ^
>  ffff8800081b0f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8800081b0f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> 
> ==================================================================
> 
> The same issue exists with l2tp_ip_bind() and l2tp_ip_bind_table.
> 
> Fixes: c51ce49735c1 ("l2tp: fix oops in L2TP IP sockets for connect() AF_UNSPEC case")
> Reported-by: Baozeng Ding <sploving1@gmail.com>
> Reported-by: Andrey Konovalov <andreyknvl@google.com>
> Tested-by: Baozeng Ding <sploving1@gmail.com>
> Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> (cherry picked from commit 32c231164b762dddefa13af5a0101032c70b50ef)
> Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
> ---
>  net/l2tp/l2tp_ip.c  | 5 +++--
>  net/l2tp/l2tp_ip6.c | 5 +++--
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
> index da1a1ce..31317f0 100644
> --- a/net/l2tp/l2tp_ip.c
> +++ b/net/l2tp/l2tp_ip.c
> @@ -249,8 +249,6 @@ static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
>  	int ret;
>  	int chk_addr_ret;
>  
> -	if (!sock_flag(sk, SOCK_ZAPPED))
> -		return -EINVAL;
>  	if (addr_len < sizeof(struct sockaddr_l2tpip))
>  		return -EINVAL;
>  	if (addr->l2tp_family != AF_INET)
> @@ -265,6 +263,9 @@ static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
>  	read_unlock_bh(&l2tp_ip_lock);
>  
>  	lock_sock(sk);
> +	if (!sock_flag(sk, SOCK_ZAPPED))
> +		goto out;
> +
>  	if (sk->sk_state != TCP_CLOSE || addr_len < sizeof(struct sockaddr_l2tpip))
>  		goto out;
>  
> diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
> index 99284c5..8e571ef 100644
> --- a/net/l2tp/l2tp_ip6.c
> +++ b/net/l2tp/l2tp_ip6.c
> @@ -264,8 +264,6 @@ static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
>  	int addr_type;
>  	int err;
>  
> -	if (!sock_flag(sk, SOCK_ZAPPED))
> -		return -EINVAL;
>  	if (addr->l2tp_family != AF_INET6)
>  		return -EINVAL;
>  	if (addr_len < sizeof(*addr))
> @@ -291,6 +289,9 @@ static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
>  	lock_sock(sk);
>  
>  	err = -EINVAL;
> +	if (!sock_flag(sk, SOCK_ZAPPED))
> +		goto out_unlock;
> +
>  	if (sk->sk_state != TCP_CLOSE)
>  		goto out_unlock;
>  
> 

Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Stefan Bader Aug. 29, 2017, 8:14 a.m. | #2
On 28.08.2017 10:10, Po-Hsu Lin wrote:
> From: Guillaume Nault <g.nault@alphalink.fr>
> 
> CVE-2016-10200
> 
> Lock socket before checking the SOCK_ZAPPED flag in l2tp_ip6_bind().
> Without lock, a concurrent call could modify the socket flags between
> the sock_flag(sk, SOCK_ZAPPED) test and the lock_sock() call. This way,
> a socket could be inserted twice in l2tp_ip6_bind_table. Releasing it
> would then leave a stale pointer there, generating use-after-free
> errors when walking through the list or modifying adjacent entries.
> 
> BUG: KASAN: use-after-free in l2tp_ip6_close+0x22e/0x290 at addr ffff8800081b0ed8
> Write of size 8 by task syz-executor/10987
> CPU: 0 PID: 10987 Comm: syz-executor Not tainted 4.8.0+ #39
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
>  ffff880031d97838 ffffffff829f835b ffff88001b5a1640 ffff8800081b0ec0
>  ffff8800081b15a0 ffff8800081b6d20 ffff880031d97860 ffffffff8174d3cc
>  ffff880031d978f0 ffff8800081b0e80 ffff88001b5a1640 ffff880031d978e0
> Call Trace:
>  [<ffffffff829f835b>] dump_stack+0xb3/0x118 lib/dump_stack.c:15
>  [<ffffffff8174d3cc>] kasan_object_err+0x1c/0x70 mm/kasan/report.c:156
>  [<     inline     >] print_address_description mm/kasan/report.c:194
>  [<ffffffff8174d666>] kasan_report_error+0x1f6/0x4d0 mm/kasan/report.c:283
>  [<     inline     >] kasan_report mm/kasan/report.c:303
>  [<ffffffff8174db7e>] __asan_report_store8_noabort+0x3e/0x40 mm/kasan/report.c:329
>  [<     inline     >] __write_once_size ./include/linux/compiler.h:249
>  [<     inline     >] __hlist_del ./include/linux/list.h:622
>  [<     inline     >] hlist_del_init ./include/linux/list.h:637
>  [<ffffffff8579047e>] l2tp_ip6_close+0x22e/0x290 net/l2tp/l2tp_ip6.c:239
>  [<ffffffff850b2dfd>] inet_release+0xed/0x1c0 net/ipv4/af_inet.c:415
>  [<ffffffff851dc5a0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:422
>  [<ffffffff84c4581d>] sock_release+0x8d/0x1d0 net/socket.c:570
>  [<ffffffff84c45976>] sock_close+0x16/0x20 net/socket.c:1017
>  [<ffffffff817a108c>] __fput+0x28c/0x780 fs/file_table.c:208
>  [<ffffffff817a1605>] ____fput+0x15/0x20 fs/file_table.c:244
>  [<ffffffff813774f9>] task_work_run+0xf9/0x170
>  [<ffffffff81324aae>] do_exit+0x85e/0x2a00
>  [<ffffffff81326dc8>] do_group_exit+0x108/0x330
>  [<ffffffff81348cf7>] get_signal+0x617/0x17a0 kernel/signal.c:2307
>  [<ffffffff811b49af>] do_signal+0x7f/0x18f0
>  [<ffffffff810039bf>] exit_to_usermode_loop+0xbf/0x150 arch/x86/entry/common.c:156
>  [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
>  [<ffffffff81006060>] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259
>  [<ffffffff85e4d726>] entry_SYSCALL_64_fastpath+0xc4/0xc6
> Object at ffff8800081b0ec0, in cache L2TP/IPv6 size: 1448
> Allocated:
> PID = 10987
>  [ 1116.897025] [<ffffffff811ddcb6>] save_stack_trace+0x16/0x20
>  [ 1116.897025] [<ffffffff8174c736>] save_stack+0x46/0xd0
>  [ 1116.897025] [<ffffffff8174c9ad>] kasan_kmalloc+0xad/0xe0
>  [ 1116.897025] [<ffffffff8174cee2>] kasan_slab_alloc+0x12/0x20
>  [ 1116.897025] [<     inline     >] slab_post_alloc_hook mm/slab.h:417
>  [ 1116.897025] [<     inline     >] slab_alloc_node mm/slub.c:2708
>  [ 1116.897025] [<     inline     >] slab_alloc mm/slub.c:2716
>  [ 1116.897025] [<ffffffff817476a8>] kmem_cache_alloc+0xc8/0x2b0 mm/slub.c:2721
>  [ 1116.897025] [<ffffffff84c4f6a9>] sk_prot_alloc+0x69/0x2b0 net/core/sock.c:1326
>  [ 1116.897025] [<ffffffff84c58ac8>] sk_alloc+0x38/0xae0 net/core/sock.c:1388
>  [ 1116.897025] [<ffffffff851ddf67>] inet6_create+0x2d7/0x1000 net/ipv6/af_inet6.c:182
>  [ 1116.897025] [<ffffffff84c4af7b>] __sock_create+0x37b/0x640 net/socket.c:1153
>  [ 1116.897025] [<     inline     >] sock_create net/socket.c:1193
>  [ 1116.897025] [<     inline     >] SYSC_socket net/socket.c:1223
>  [ 1116.897025] [<ffffffff84c4b46f>] SyS_socket+0xef/0x1b0 net/socket.c:1203
>  [ 1116.897025] [<ffffffff85e4d685>] entry_SYSCALL_64_fastpath+0x23/0xc6
> Freed:
> PID = 10987
>  [ 1116.897025] [<ffffffff811ddcb6>] save_stack_trace+0x16/0x20
>  [ 1116.897025] [<ffffffff8174c736>] save_stack+0x46/0xd0
>  [ 1116.897025] [<ffffffff8174cf61>] kasan_slab_free+0x71/0xb0
>  [ 1116.897025] [<     inline     >] slab_free_hook mm/slub.c:1352
>  [ 1116.897025] [<     inline     >] slab_free_freelist_hook mm/slub.c:1374
>  [ 1116.897025] [<     inline     >] slab_free mm/slub.c:2951
>  [ 1116.897025] [<ffffffff81748b28>] kmem_cache_free+0xc8/0x330 mm/slub.c:2973
>  [ 1116.897025] [<     inline     >] sk_prot_free net/core/sock.c:1369
>  [ 1116.897025] [<ffffffff84c541eb>] __sk_destruct+0x32b/0x4f0 net/core/sock.c:1444
>  [ 1116.897025] [<ffffffff84c5aca4>] sk_destruct+0x44/0x80 net/core/sock.c:1452
>  [ 1116.897025] [<ffffffff84c5ad33>] __sk_free+0x53/0x220 net/core/sock.c:1460
>  [ 1116.897025] [<ffffffff84c5af23>] sk_free+0x23/0x30 net/core/sock.c:1471
>  [ 1116.897025] [<ffffffff84c5cb6c>] sk_common_release+0x28c/0x3e0 ./include/net/sock.h:1589
>  [ 1116.897025] [<ffffffff8579044e>] l2tp_ip6_close+0x1fe/0x290 net/l2tp/l2tp_ip6.c:243
>  [ 1116.897025] [<ffffffff850b2dfd>] inet_release+0xed/0x1c0 net/ipv4/af_inet.c:415
>  [ 1116.897025] [<ffffffff851dc5a0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:422
>  [ 1116.897025] [<ffffffff84c4581d>] sock_release+0x8d/0x1d0 net/socket.c:570
>  [ 1116.897025] [<ffffffff84c45976>] sock_close+0x16/0x20 net/socket.c:1017
>  [ 1116.897025] [<ffffffff817a108c>] __fput+0x28c/0x780 fs/file_table.c:208
>  [ 1116.897025] [<ffffffff817a1605>] ____fput+0x15/0x20 fs/file_table.c:244
>  [ 1116.897025] [<ffffffff813774f9>] task_work_run+0xf9/0x170
>  [ 1116.897025] [<ffffffff81324aae>] do_exit+0x85e/0x2a00
>  [ 1116.897025] [<ffffffff81326dc8>] do_group_exit+0x108/0x330
>  [ 1116.897025] [<ffffffff81348cf7>] get_signal+0x617/0x17a0 kernel/signal.c:2307
>  [ 1116.897025] [<ffffffff811b49af>] do_signal+0x7f/0x18f0
>  [ 1116.897025] [<ffffffff810039bf>] exit_to_usermode_loop+0xbf/0x150 arch/x86/entry/common.c:156
>  [ 1116.897025] [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
>  [ 1116.897025] [<ffffffff81006060>] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259
>  [ 1116.897025] [<ffffffff85e4d726>] entry_SYSCALL_64_fastpath+0xc4/0xc6
> Memory state around the buggy address:
>  ffff8800081b0d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8800081b0e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> ffff8800081b0e80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>                                                     ^
>  ffff8800081b0f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8800081b0f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> 
> ==================================================================
> 
> The same issue exists with l2tp_ip_bind() and l2tp_ip_bind_table.
> 
> Fixes: c51ce49735c1 ("l2tp: fix oops in L2TP IP sockets for connect() AF_UNSPEC case")
> Reported-by: Baozeng Ding <sploving1@gmail.com>
> Reported-by: Andrey Konovalov <andreyknvl@google.com>
> Tested-by: Baozeng Ding <sploving1@gmail.com>
> Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> (cherry picked from commit 32c231164b762dddefa13af5a0101032c70b50ef)
> Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>

> ---
>  net/l2tp/l2tp_ip.c  | 5 +++--
>  net/l2tp/l2tp_ip6.c | 5 +++--
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
> index da1a1ce..31317f0 100644
> --- a/net/l2tp/l2tp_ip.c
> +++ b/net/l2tp/l2tp_ip.c
> @@ -249,8 +249,6 @@ static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
>  	int ret;
>  	int chk_addr_ret;
>  
> -	if (!sock_flag(sk, SOCK_ZAPPED))
> -		return -EINVAL;
>  	if (addr_len < sizeof(struct sockaddr_l2tpip))
>  		return -EINVAL;
>  	if (addr->l2tp_family != AF_INET)
> @@ -265,6 +263,9 @@ static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
>  	read_unlock_bh(&l2tp_ip_lock);
>  
>  	lock_sock(sk);
> +	if (!sock_flag(sk, SOCK_ZAPPED))
> +		goto out;
> +
>  	if (sk->sk_state != TCP_CLOSE || addr_len < sizeof(struct sockaddr_l2tpip))
>  		goto out;
>  
> diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
> index 99284c5..8e571ef 100644
> --- a/net/l2tp/l2tp_ip6.c
> +++ b/net/l2tp/l2tp_ip6.c
> @@ -264,8 +264,6 @@ static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
>  	int addr_type;
>  	int err;
>  
> -	if (!sock_flag(sk, SOCK_ZAPPED))
> -		return -EINVAL;
>  	if (addr->l2tp_family != AF_INET6)
>  		return -EINVAL;
>  	if (addr_len < sizeof(*addr))
> @@ -291,6 +289,9 @@ static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
>  	lock_sock(sk);
>  
>  	err = -EINVAL;
> +	if (!sock_flag(sk, SOCK_ZAPPED))
> +		goto out_unlock;
> +
>  	if (sk->sk_state != TCP_CLOSE)
>  		goto out_unlock;
>  
>
Kleber Sacilotto de Souza Aug. 29, 2017, 2:59 p.m. | #3
Applied on trusty/master-next branch. Thanks.

Patch

==================================================================

The same issue exists with l2tp_ip_bind() and l2tp_ip_bind_table.

Fixes: c51ce49735c1 ("l2tp: fix oops in L2TP IP sockets for connect() AF_UNSPEC case")
Reported-by: Baozeng Ding <sploving1@gmail.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Baozeng Ding <sploving1@gmail.com>
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 32c231164b762dddefa13af5a0101032c70b50ef)
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
---
 net/l2tp/l2tp_ip.c  | 5 +++--
 net/l2tp/l2tp_ip6.c | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index da1a1ce..31317f0 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -249,8 +249,6 @@  static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	int ret;
 	int chk_addr_ret;
 
-	if (!sock_flag(sk, SOCK_ZAPPED))
-		return -EINVAL;
 	if (addr_len < sizeof(struct sockaddr_l2tpip))
 		return -EINVAL;
 	if (addr->l2tp_family != AF_INET)
@@ -265,6 +263,9 @@  static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	read_unlock_bh(&l2tp_ip_lock);
 
 	lock_sock(sk);
+	if (!sock_flag(sk, SOCK_ZAPPED))
+		goto out;
+
 	if (sk->sk_state != TCP_CLOSE || addr_len < sizeof(struct sockaddr_l2tpip))
 		goto out;
 
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index 99284c5..8e571ef 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -264,8 +264,6 @@  static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	int addr_type;
 	int err;
 
-	if (!sock_flag(sk, SOCK_ZAPPED))
-		return -EINVAL;
 	if (addr->l2tp_family != AF_INET6)
 		return -EINVAL;
 	if (addr_len < sizeof(*addr))
@@ -291,6 +289,9 @@  static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	lock_sock(sk);
 
 	err = -EINVAL;
+	if (!sock_flag(sk, SOCK_ZAPPED))
+		goto out_unlock;
+
 	if (sk->sk_state != TCP_CLOSE)
 		goto out_unlock;