[PATCH net] sctp: initialize _pad of sockaddr_in before copying to user memory

[PATCH net] sctp: initialize _pad of sockaddr_in before copying to user memory

[Xin Long]

Syzbot report a kernel-infoleak:

  BUG: KMSAN: kernel-infoleak in _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
  Call Trace:
    _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
    copy_to_user include/linux/uaccess.h:174 [inline]
    sctp_getsockopt_peer_addrs net/sctp/socket.c:5911 [inline]
    sctp_getsockopt+0x1668e/0x17f70 net/sctp/socket.c:7562
    ...
  Uninit was stored to memory at:
    sctp_transport_init net/sctp/transport.c:61 [inline]
    sctp_transport_new+0x16d/0x9a0 net/sctp/transport.c:115
    sctp_assoc_add_peer+0x532/0x1f70 net/sctp/associola.c:637
    sctp_process_param net/sctp/sm_make_chunk.c:2548 [inline]
    sctp_process_init+0x1a1b/0x3ed0 net/sctp/sm_make_chunk.c:2361
    ...
  Bytes 8-15 of 16 are uninitialized

It was caused by that th _pad field (the 8-15 bytes) of a v4 addr (saved in
struct sockaddr_in) wasn't initialized, but directly copied to user memory
in sctp_getsockopt_peer_addrs().

So fix it by calling memset(addr->v4.sin_zero, 0, 8) to initialize _pad of
sockaddr_in before copying it to user memory in sctp_v4_addr_to_user(), as
sctp_v6_addr_to_user() does.

Reported-by: syzbot+86b5c7c236a22616a72f@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 net/sctp/protocol.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 6abc8b2..951afde 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -600,6 +600,7 @@ static struct sock *sctp_v4_create_accept_sk(struct sock *sk,
 static int sctp_v4_addr_to_user(struct sctp_sock *sp, union sctp_addr *addr)
 {
 	/* No address mapping for V4 sockets */
+	memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
 	return sizeof(struct sockaddr_in);
 }
 
-- 
2.1.0

Re: [PATCH net] sctp: initialize _pad of sockaddr_in before copying to user memory

[Alexander Potapenko]

On Sun, Mar 31, 2019 at 10:58 AM Xin Long <lucien.xin@gmail.com> wrote:
>
> Syzbot report a kernel-infoleak:
>
>   BUG: KMSAN: kernel-infoleak in _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
>   Call Trace:
>     _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
>     copy_to_user include/linux/uaccess.h:174 [inline]
>     sctp_getsockopt_peer_addrs net/sctp/socket.c:5911 [inline]
>     sctp_getsockopt+0x1668e/0x17f70 net/sctp/socket.c:7562
>     ...
>   Uninit was stored to memory at:
>     sctp_transport_init net/sctp/transport.c:61 [inline]
>     sctp_transport_new+0x16d/0x9a0 net/sctp/transport.c:115
>     sctp_assoc_add_peer+0x532/0x1f70 net/sctp/associola.c:637
>     sctp_process_param net/sctp/sm_make_chunk.c:2548 [inline]
>     sctp_process_init+0x1a1b/0x3ed0 net/sctp/sm_make_chunk.c:2361
>     ...
>   Bytes 8-15 of 16 are uninitialized
>
> It was caused by that th _pad field (the 8-15 bytes) of a v4 addr (saved in
> struct sockaddr_in) wasn't initialized, but directly copied to user memory
> in sctp_getsockopt_peer_addrs().
>
> So fix it by calling memset(addr->v4.sin_zero, 0, 8) to initialize _pad of
> sockaddr_in before copying it to user memory in sctp_v4_addr_to_user(), as
> sctp_v6_addr_to_user() does.
>
> Reported-by: syzbot+86b5c7c236a22616a72f@syzkaller.appspotmail.com
> Signed-off-by: Xin Long <lucien.xin@gmail.com>
Tested-by: Alexander Potapenko <glider@google.com>
> ---
>  net/sctp/protocol.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index 6abc8b2..951afde 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -600,6 +600,7 @@ static struct sock *sctp_v4_create_accept_sk(struct sock *sk,
>  static int sctp_v4_addr_to_user(struct sctp_sock *sp, union sctp_addr *addr)
>  {
>         /* No address mapping for V4 sockets */
> +       memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
>         return sizeof(struct sockaddr_in);
>  }
>
> --
> 2.1.0
>
> --
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-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Re: [PATCH net] sctp: initialize _pad of sockaddr_in before copying to user memory

[Neil Horman]

On Sun, Mar 31, 2019 at 04:58:15PM +0800, Xin Long wrote:
> Syzbot report a kernel-infoleak:
> 
>   BUG: KMSAN: kernel-infoleak in _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
>   Call Trace:
>     _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
>     copy_to_user include/linux/uaccess.h:174 [inline]
>     sctp_getsockopt_peer_addrs net/sctp/socket.c:5911 [inline]
>     sctp_getsockopt+0x1668e/0x17f70 net/sctp/socket.c:7562
>     ...
>   Uninit was stored to memory at:
>     sctp_transport_init net/sctp/transport.c:61 [inline]
>     sctp_transport_new+0x16d/0x9a0 net/sctp/transport.c:115
>     sctp_assoc_add_peer+0x532/0x1f70 net/sctp/associola.c:637
>     sctp_process_param net/sctp/sm_make_chunk.c:2548 [inline]
>     sctp_process_init+0x1a1b/0x3ed0 net/sctp/sm_make_chunk.c:2361
>     ...
>   Bytes 8-15 of 16 are uninitialized
> 
> It was caused by that th _pad field (the 8-15 bytes) of a v4 addr (saved in
> struct sockaddr_in) wasn't initialized, but directly copied to user memory
> in sctp_getsockopt_peer_addrs().
> 
> So fix it by calling memset(addr->v4.sin_zero, 0, 8) to initialize _pad of
> sockaddr_in before copying it to user memory in sctp_v4_addr_to_user(), as
> sctp_v6_addr_to_user() does.
> 
> Reported-by: syzbot+86b5c7c236a22616a72f@syzkaller.appspotmail.com
> Signed-off-by: Xin Long <lucien.xin@gmail.com>
> ---
>  net/sctp/protocol.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index 6abc8b2..951afde 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -600,6 +600,7 @@ static struct sock *sctp_v4_create_accept_sk(struct sock *sk,
>  static int sctp_v4_addr_to_user(struct sctp_sock *sp, union sctp_addr *addr)
>  {
>  	/* No address mapping for V4 sockets */
> +	memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
>  	return sizeof(struct sockaddr_in);
>  }
>  
> -- 
> 2.1.0
> 
> 
Acked-by: Neil Horman <nhorman@tuxdriver.com>

Re: [PATCH net] sctp: initialize _pad of sockaddr_in before copying to user memory

[David Miller]

From: Xin Long <lucien.xin@gmail.com>
Date: Sun, 31 Mar 2019 16:58:15 +0800

> Syzbot report a kernel-infoleak:
> 
>   BUG: KMSAN: kernel-infoleak in _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
>   Call Trace:
>     _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
>     copy_to_user include/linux/uaccess.h:174 [inline]
>     sctp_getsockopt_peer_addrs net/sctp/socket.c:5911 [inline]
>     sctp_getsockopt+0x1668e/0x17f70 net/sctp/socket.c:7562
>     ...
>   Uninit was stored to memory at:
>     sctp_transport_init net/sctp/transport.c:61 [inline]
>     sctp_transport_new+0x16d/0x9a0 net/sctp/transport.c:115
>     sctp_assoc_add_peer+0x532/0x1f70 net/sctp/associola.c:637
>     sctp_process_param net/sctp/sm_make_chunk.c:2548 [inline]
>     sctp_process_init+0x1a1b/0x3ed0 net/sctp/sm_make_chunk.c:2361
>     ...
>   Bytes 8-15 of 16 are uninitialized
> 
> It was caused by that th _pad field (the 8-15 bytes) of a v4 addr (saved in
> struct sockaddr_in) wasn't initialized, but directly copied to user memory
> in sctp_getsockopt_peer_addrs().
> 
> So fix it by calling memset(addr->v4.sin_zero, 0, 8) to initialize _pad of
> sockaddr_in before copying it to user memory in sctp_v4_addr_to_user(), as
> sctp_v6_addr_to_user() does.
> 
> Reported-by: syzbot+86b5c7c236a22616a72f@syzkaller.appspotmail.com
> Signed-off-by: Xin Long <lucien.xin@gmail.com>

Applied and queued up for -stable, thanks Xin!