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[PATCH] mptcp: fix possible NULL dereferences

Matthieu Baerts (NGI0) posted 1 patch 1 week, 6 days ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/multipath-tcp/mptcp_net-next tags/patchew/20240506135129.3528973-2-matttbe@kernel.org
net/mptcp/subflow.c | 32 +++++++++++++++++---------------
1 file changed, 17 insertions(+), 15 deletions(-)
[PATCH] mptcp: fix possible NULL dereferences
Posted by Matthieu Baerts (NGI0) 1 week, 6 days ago 
From: Eric Dumazet <edumazet@google.com>

subflow_add_reset_reason(skb, ...) can fail.

We can not assume mptcp_get_ext(skb) always return a non NULL pointer.

syzbot reported:

general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
CPU: 0 PID: 5098 Comm: syz-executor132 Not tainted 6.9.0-rc6-syzkaller-01478-gcdc74c9d06e7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
 RIP: 0010:subflow_v6_route_req+0x2c7/0x490 net/mptcp/subflow.c:388
Code: 8d 7b 07 48 89 f8 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 c0 01 00 00 0f b6 43 07 48 8d 1c c3 48 83 c3 18 48 89 d8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 84 01 00 00 0f b6 5b 01 83 e3 0f 48 89
RSP: 0018:ffffc9000362eb68 EFLAGS: 00010206
RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff888022039e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88807d961140 R08: ffffffff8b6cb76b R09: 1ffff1100fb2c230
R10: dffffc0000000000 R11: ffffed100fb2c231 R12: dffffc0000000000
R13: ffff888022bfe273 R14: ffff88802cf9cc80 R15: ffff88802ad5a700
FS:  0000555587ad2380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f420c3f9720 CR3: 0000000022bfc000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  tcp_conn_request+0xf07/0x32c0 net/ipv4/tcp_input.c:7180
  tcp_rcv_state_process+0x183c/0x4500 net/ipv4/tcp_input.c:6663
  tcp_v6_do_rcv+0x8b2/0x1310 net/ipv6/tcp_ipv6.c:1673
  tcp_v6_rcv+0x22b4/0x30b0 net/ipv6/tcp_ipv6.c:1910
  ip6_protocol_deliver_rcu+0xc76/0x1570 net/ipv6/ip6_input.c:438
  ip6_input_finish+0x186/0x2d0 net/ipv6/ip6_input.c:483
  NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
  NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
  __netif_receive_skb_one_core net/core/dev.c:5625 [inline]
  __netif_receive_skb+0x1ea/0x650 net/core/dev.c:5739
  netif_receive_skb_internal net/core/dev.c:5825 [inline]
  netif_receive_skb+0x1e8/0x890 net/core/dev.c:5885
  tun_rx_batched+0x1b7/0x8f0 drivers/net/tun.c:1549
  tun_get_user+0x2f35/0x4560 drivers/net/tun.c:2002
  tun_chr_write_iter+0x113/0x1f0 drivers/net/tun.c:2048
  call_write_iter include/linux/fs.h:2110 [inline]
  new_sync_write fs/read_write.c:497 [inline]
  vfs_write+0xa84/0xcb0 fs/read_write.c:590
  ksys_write+0x1a0/0x2c0 fs/read_write.c:643
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: 3e140491dd80 ("mptcp: support rstreason for passive reset")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jason Xing <kernelxing@tencent.com>
Cc: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240506123032.3351895-1-edumazet@google.com
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/subflow.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 7987342f4526..422aa06da93b 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -287,6 +287,16 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,
 }
 EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
 
+static enum sk_rst_reason mptcp_get_rst_reason(const struct sk_buff *skb)
+{
+	const struct mptcp_ext *mpext = mptcp_get_ext(skb);
+
+	if (!mpext)
+		return SK_RST_REASON_NOT_SPECIFIED;
+
+	return sk_rst_convert_mptcp_reason(mpext->reset_reason);
+}
+
 static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
 					      struct sk_buff *skb,
 					      struct flowi *fl,
@@ -308,13 +318,9 @@ static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
 		return dst;
 
 	dst_release(dst);
-	if (!req->syncookie) {
-		struct mptcp_ext *mpext = mptcp_get_ext(skb);
-		enum sk_rst_reason reason;
-
-		reason = sk_rst_convert_mptcp_reason(mpext->reset_reason);
-		tcp_request_sock_ops.send_reset(sk, skb, reason);
-	}
+	if (!req->syncookie)
+		tcp_request_sock_ops.send_reset(sk, skb,
+						mptcp_get_rst_reason(skb));
 	return NULL;
 }
 
@@ -381,13 +387,9 @@ static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
 		return dst;
 
 	dst_release(dst);
-	if (!req->syncookie) {
-		struct mptcp_ext *mpext = mptcp_get_ext(skb);
-		enum sk_rst_reason reason;
-
-		reason = sk_rst_convert_mptcp_reason(mpext->reset_reason);
-		tcp6_request_sock_ops.send_reset(sk, skb, reason);
-	}
+	if (!req->syncookie)
+		tcp6_request_sock_ops.send_reset(sk, skb,
+						 mptcp_get_rst_reason(skb));
 	return NULL;
 }
 #endif
@@ -923,7 +925,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 	tcp_rsk(req)->drop_req = true;
 	inet_csk_prepare_for_destroy_sock(child);
 	tcp_done(child);
-	reason = sk_rst_convert_mptcp_reason(mptcp_get_ext(skb)->reset_reason);
+	reason = mptcp_get_rst_reason(skb);
 	req->rsk_ops->send_reset(sk, skb, reason);
 
 	/* The last child reference will be released by the caller */
-- 
2.43.0
Re: [PATCH] mptcp: fix possible NULL dereferences
Posted by MPTCP CI 1 week, 6 days ago 
Hi Eric,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal: Unstable: 1 failed test(s): selftest_simult_flows 🔴
- KVM Validation: debug: Success! ✅
- KVM Validation: btf (only bpftest_all): Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/8970381678

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/0b805722de2c
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=850808


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)
Re: [PATCH] mptcp: fix possible NULL dereferences
Posted by Matthieu Baerts 1 week, 6 days ago 
I forgot to add: this is just to have our CI checking this patch.

On 06/05/2024 15:51, Matthieu Baerts (NGI0) wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> subflow_add_reset_reason(skb, ...) can fail.
> 
> We can not assume mptcp_get_ext(skb) always return a non NULL pointer.
> 
> syzbot reported:
> 
> general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
> CPU: 0 PID: 5098 Comm: syz-executor132 Not tainted 6.9.0-rc6-syzkaller-01478-gcdc74c9d06e7 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
>  RIP: 0010:subflow_v6_route_req+0x2c7/0x490 net/mptcp/subflow.c:388
> Code: 8d 7b 07 48 89 f8 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 c0 01 00 00 0f b6 43 07 48 8d 1c c3 48 83 c3 18 48 89 d8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 84 01 00 00 0f b6 5b 01 83 e3 0f 48 89
> RSP: 0018:ffffc9000362eb68 EFLAGS: 00010206
> RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff888022039e00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffff88807d961140 R08: ffffffff8b6cb76b R09: 1ffff1100fb2c230
> R10: dffffc0000000000 R11: ffffed100fb2c231 R12: dffffc0000000000
> R13: ffff888022bfe273 R14: ffff88802cf9cc80 R15: ffff88802ad5a700
> FS:  0000555587ad2380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f420c3f9720 CR3: 0000000022bfc000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>   tcp_conn_request+0xf07/0x32c0 net/ipv4/tcp_input.c:7180
>   tcp_rcv_state_process+0x183c/0x4500 net/ipv4/tcp_input.c:6663
>   tcp_v6_do_rcv+0x8b2/0x1310 net/ipv6/tcp_ipv6.c:1673
>   tcp_v6_rcv+0x22b4/0x30b0 net/ipv6/tcp_ipv6.c:1910
>   ip6_protocol_deliver_rcu+0xc76/0x1570 net/ipv6/ip6_input.c:438
>   ip6_input_finish+0x186/0x2d0 net/ipv6/ip6_input.c:483
>   NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
>   NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
>   __netif_receive_skb_one_core net/core/dev.c:5625 [inline]
>   __netif_receive_skb+0x1ea/0x650 net/core/dev.c:5739
>   netif_receive_skb_internal net/core/dev.c:5825 [inline]
>   netif_receive_skb+0x1e8/0x890 net/core/dev.c:5885
>   tun_rx_batched+0x1b7/0x8f0 drivers/net/tun.c:1549
>   tun_get_user+0x2f35/0x4560 drivers/net/tun.c:2002
>   tun_chr_write_iter+0x113/0x1f0 drivers/net/tun.c:2048
>   call_write_iter include/linux/fs.h:2110 [inline]
>   new_sync_write fs/read_write.c:497 [inline]
>   vfs_write+0xa84/0xcb0 fs/read_write.c:590
>   ksys_write+0x1a0/0x2c0 fs/read_write.c:643
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Fixes: 3e140491dd80 ("mptcp: support rstreason for passive reset")
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Jason Xing <kernelxing@tencent.com>
> Cc: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Link: https://lore.kernel.org/r/20240506123032.3351895-1-edumazet@google.com
> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> ---
>  net/mptcp/subflow.c | 32 +++++++++++++++++---------------
>  1 file changed, 17 insertions(+), 15 deletions(-)
> 
> diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
> index 7987342f4526..422aa06da93b 100644
> --- a/net/mptcp/subflow.c
> +++ b/net/mptcp/subflow.c
> @@ -287,6 +287,16 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,
>  }
>  EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
>  
> +static enum sk_rst_reason mptcp_get_rst_reason(const struct sk_buff *skb)
> +{
> +	const struct mptcp_ext *mpext = mptcp_get_ext(skb);
> +
> +	if (!mpext)
> +		return SK_RST_REASON_NOT_SPECIFIED;
> +
> +	return sk_rst_convert_mptcp_reason(mpext->reset_reason);
> +}
> +
>  static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
>  					      struct sk_buff *skb,
>  					      struct flowi *fl,
> @@ -308,13 +318,9 @@ static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
>  		return dst;
>  
>  	dst_release(dst);
> -	if (!req->syncookie) {
> -		struct mptcp_ext *mpext = mptcp_get_ext(skb);
> -		enum sk_rst_reason reason;
> -
> -		reason = sk_rst_convert_mptcp_reason(mpext->reset_reason);
> -		tcp_request_sock_ops.send_reset(sk, skb, reason);
> -	}
> +	if (!req->syncookie)
> +		tcp_request_sock_ops.send_reset(sk, skb,
> +						mptcp_get_rst_reason(skb));
>  	return NULL;
>  }
>  
> @@ -381,13 +387,9 @@ static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
>  		return dst;
>  
>  	dst_release(dst);
> -	if (!req->syncookie) {
> -		struct mptcp_ext *mpext = mptcp_get_ext(skb);
> -		enum sk_rst_reason reason;
> -
> -		reason = sk_rst_convert_mptcp_reason(mpext->reset_reason);
> -		tcp6_request_sock_ops.send_reset(sk, skb, reason);
> -	}
> +	if (!req->syncookie)
> +		tcp6_request_sock_ops.send_reset(sk, skb,
> +						 mptcp_get_rst_reason(skb));
>  	return NULL;
>  }
>  #endif
> @@ -923,7 +925,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
>  	tcp_rsk(req)->drop_req = true;
>  	inet_csk_prepare_for_destroy_sock(child);
>  	tcp_done(child);
> -	reason = sk_rst_convert_mptcp_reason(mptcp_get_ext(skb)->reset_reason);
> +	reason = mptcp_get_rst_reason(skb);
>  	req->rsk_ops->send_reset(sk, skb, reason);
>  
>  	/* The last child reference will be released by the caller */

Cheers,
Matt
-- 
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