Re: [PATCH net] net: selinux: fix memory leak in selinux_netlbl_socket_post_create()

[Paul Moore]

On Wed, Mar 6, 2019 at 9:44 PM Mao Wenan <maowenan@xxxxxxxxxx> wrote:
>
> If netlbl_sock_setattr() is failed, it directly returns rc and forgets
> to free secattr.
>
> BUG: memory leak
> unreferenced object 0xffff8883c3ea4200 (size 2664):
>   comm "syz-executor.2", pid 8813, jiffies 4297264419 (age 156.090s)
>   hex dump (first 32 bytes):
>     7f 00 00 01 7f 00 00 01 eb 7f ed 71 4e 24 00 00  ...........qN$..
>     02 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00  ...@............
>   backtrace:
>     [<000000004c0228da>] sk_alloc+0x3d/0xc00 net/core/sock.c:1523
>     [<00000000535a3da2>] inet_create+0x339/0xe10 net/ipv4/af_inet.c:321
>     [<000000009aec3cfe>] __sock_create+0x3fa/0x790 net/socket.c:1275
>     [<000000004274b384>] sock_create net/socket.c:1315 [inline]
>     [<000000004274b384>] __sys_socket+0xe7/0x1d0 net/socket.c:1345
>     [<00000000b3fdc826>] __do_sys_socket net/socket.c:1354 [inline]
>     [<00000000b3fdc826>] __se_sys_socket net/socket.c:1352 [inline]
>     [<00000000b3fdc826>] __x64_sys_socket+0x74/0xb0 net/socket.c:1352
>     [<000000004ae3186e>] do_syscall_64+0xc8/0x580 arch/x86/entry/common.c:290
>     [<00000000bc0d2230>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
>     [<00000000f737e62f>] 0xffffffffffffffff
>
> BUG: memory leak
> unreferenced object 0xffff8883de23d570 (size 32):
>   comm "syz-executor.2", pid 8813, jiffies 4297264419 (age 156.090s)
>   hex dump (first 32 bytes):
>     02 00 00 00 00 00 00 00 60 a9 40 ce 83 88 ff ff  ........`.@.....
>     01 00 00 00 03 00 00 00 10 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<0000000035ba8b75>] security_sk_alloc+0x5e/0xb0 security/security.c:1473
>     [<00000000302cc426>] sk_prot_alloc+0x8e/0x290 net/core/sock.c:1472
>     [<000000004c0228da>] sk_alloc+0x3d/0xc00 net/core/sock.c:1523
>     [<00000000535a3da2>] inet_create+0x339/0xe10 net/ipv4/af_inet.c:321
>     [<000000009aec3cfe>] __sock_create+0x3fa/0x790 net/socket.c:1275
>     [<000000004274b384>] sock_create net/socket.c:1315 [inline]
>     [<000000004274b384>] __sys_socket+0xe7/0x1d0 net/socket.c:1345
>     [<00000000b3fdc826>] __do_sys_socket net/socket.c:1354 [inline]
>     [<00000000b3fdc826>] __se_sys_socket net/socket.c:1352 [inline]
>     [<00000000b3fdc826>] __x64_sys_socket+0x74/0xb0 net/socket.c:1352
>     [<000000004ae3186e>] do_syscall_64+0xc8/0x580 arch/x86/entry/common.c:290
>     [<00000000bc0d2230>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
>     [<00000000f737e62f>] 0xffffffffffffffff
>
> BUG: memory leak
> unreferenced object 0xffff8883ce40a960 (size 64):
>   comm "syz-executor.2", pid 8813, jiffies 4297264420 (age 156.089s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<0000000029add401>] selinux_netlbl_socket_post_create+0x68/0x130 security/selinux/netlabel.c:416
>     [<000000005368a19c>] selinux_socket_post_create+0x31a/0x7f0 security/selinux/hooks.c:4597
>     [<00000000bd4730e2>] security_socket_post_create+0x70/0xc0 security/security.c:1385
>     [<00000000671052a4>] __sock_create+0x5a6/0x790 net/socket.c:1291
>     [<000000004274b384>] sock_create net/socket.c:1315 [inline]
>     [<000000004274b384>] __sys_socket+0xe7/0x1d0 net/socket.c:1345
>     [<00000000b3fdc826>] __do_sys_socket net/socket.c:1354 [inline]
>     [<00000000b3fdc826>] __se_sys_socket net/socket.c:1352 [inline]
>     [<00000000b3fdc826>] __x64_sys_socket+0x74/0xb0 net/socket.c:1352
>     [<000000004ae3186e>] do_syscall_64+0xc8/0x580 arch/x86/entry/common.c:290
>     [<00000000bc0d2230>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
>     [<00000000f737e62f>] 0xffffffffffffffff
>
> Fixes: 389fb800ac8b("netlabel: Label incoming TCP connections correctly in SELinux")
> Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
> Signed-off-by: Mao Wenan <maowenan@xxxxxxxxxx>
> ---
>  security/selinux/netlabel.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/security/selinux/netlabel.c b/security/selinux/netlabel.c
> index 186e727b737b..f3da05338580 100644
> --- a/security/selinux/netlabel.c
> +++ b/security/selinux/netlabel.c
> @@ -426,6 +426,9 @@ int selinux_netlbl_socket_post_create(struct sock *sk, u16 family)
>                 rc = 0;
>                 break;
>         }
> +       if (rc != 0) {
> +               netlbl_secattr_free(secattr);
> +       }

This is likely going to cause a problem as the
sock->sk_security->nlbl_secattr still has a reference to the secattr
pointer you are releasing here.  Assuming things are working correctly
elsewhere, I believe freeing secattr here will result in a double free
when the network stacks cleans up after the failed socket creation
(via the sock_release() call in the error handling code).

It looks like you may have found this via a test tool (syzbot?), do
you have a reproducer you can share?

-- 
paul moore
www.paul-moore.com