[PATCH 5.15 0/2] netlink, fix issues caught by syzbot

[PATCH 5.15 0/2] netlink, fix issues caught by syzbot

[Yenchia Chen]

From: "yenchia.chen" <yenchia.chen@mediatek.com>

Hi,

We think 5.15.y could pick these commits.

Below is the mainline commit:

netlink: annotate lockless accesses to nlk->max_recvmsg_len
[ Upstream commit a1865f2e7d10dde00d35a2122b38d2e469ae67ed ]

netlink: annotate data-races around sk->sk_err
[ Upstream commit d0f95894fda7d4f895b29c1097f92d7fee278cb2 ]

Eric Dumazet (2):
  netlink: annotate lockless accesses to nlk->max_recvmsg_len
  netlink: annotate data-races around sk->sk_err

 net/netlink/af_netlink.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

-- 
2.18.0


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[PATCH 5.15 1/2] netlink: annotate lockless accesses to nlk->max_recvmsg_len

[Yenchia Chen]

From: Eric Dumazet <edumazet@google.com>

syzbot reported a data-race in data-race in netlink_recvmsg() [1]

Indeed, netlink_recvmsg() can be run concurrently,
and netlink_dump() also needs protection.

[1]
BUG: KCSAN: data-race in netlink_recvmsg / netlink_recvmsg

read to 0xffff888141840b38 of 8 bytes by task 23057 on cpu 0:
netlink_recvmsg+0xea/0x730 net/netlink/af_netlink.c:1988
sock_recvmsg_nosec net/socket.c:1017 [inline]
sock_recvmsg net/socket.c:1038 [inline]
__sys_recvfrom+0x1ee/0x2e0 net/socket.c:2194
__do_sys_recvfrom net/socket.c:2212 [inline]
__se_sys_recvfrom net/socket.c:2208 [inline]
__x64_sys_recvfrom+0x78/0x90 net/socket.c:2208
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffff888141840b38 of 8 bytes by task 23037 on cpu 1:
netlink_recvmsg+0x114/0x730 net/netlink/af_netlink.c:1989
sock_recvmsg_nosec net/socket.c:1017 [inline]
sock_recvmsg net/socket.c:1038 [inline]
____sys_recvmsg+0x156/0x310 net/socket.c:2720
___sys_recvmsg net/socket.c:2762 [inline]
do_recvmmsg+0x2e5/0x710 net/socket.c:2856
__sys_recvmmsg net/socket.c:2935 [inline]
__do_sys_recvmmsg net/socket.c:2958 [inline]
__se_sys_recvmmsg net/socket.c:2951 [inline]
__x64_sys_recvmmsg+0xe2/0x160 net/socket.c:2951
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000000 -> 0x0000000000001000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23037 Comm: syz-executor.2 Not tainted 6.3.0-rc4-syzkaller-00195-g5a57b48fdfcb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023

Fixes: 9063e21fb026 ("netlink: autosize skb lengthes")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230403214643.768555-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: yenchia.chen <yenchia.chen@mediatek.com>
---
 net/netlink/af_netlink.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 82df02695bbd..56ba8a6396ca 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1935,7 +1935,7 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	struct sock *sk = sock->sk;
 	struct netlink_sock *nlk = nlk_sk(sk);
 	int noblock = flags & MSG_DONTWAIT;
-	size_t copied;
+	size_t copied, max_recvmsg_len;
 	struct sk_buff *skb, *data_skb;
 	int err, ret;
 
@@ -1968,9 +1968,10 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 #endif
 
 	/* Record the max length of recvmsg() calls for future allocations */
-	nlk->max_recvmsg_len = max(nlk->max_recvmsg_len, len);
-	nlk->max_recvmsg_len = min_t(size_t, nlk->max_recvmsg_len,
-				     SKB_WITH_OVERHEAD(32768));
+	max_recvmsg_len = max(READ_ONCE(nlk->max_recvmsg_len), len);
+	max_recvmsg_len = min_t(size_t, max_recvmsg_len,
+				SKB_WITH_OVERHEAD(32768));
+	WRITE_ONCE(nlk->max_recvmsg_len, max_recvmsg_len);
 
 	copied = data_skb->len;
 	if (len < copied) {
@@ -2219,6 +2220,7 @@ static int netlink_dump(struct sock *sk)
 	struct netlink_ext_ack extack = {};
 	struct netlink_callback *cb;
 	struct sk_buff *skb = NULL;
+	size_t max_recvmsg_len;
 	struct module *module;
 	int err = -ENOBUFS;
 	int alloc_min_size;
@@ -2241,8 +2243,9 @@ static int netlink_dump(struct sock *sk)
 	cb = &nlk->cb;
 	alloc_min_size = max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE);
 
-	if (alloc_min_size < nlk->max_recvmsg_len) {
-		alloc_size = nlk->max_recvmsg_len;
+	max_recvmsg_len = READ_ONCE(nlk->max_recvmsg_len);
+	if (alloc_min_size < max_recvmsg_len) {
+		alloc_size = max_recvmsg_len;
 		skb = alloc_skb(alloc_size,
 				(GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) |
 				__GFP_NOWARN | __GFP_NORETRY);
-- 
2.18.0


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[PATCH 5.15 2/2] netlink: annotate data-races around sk->sk_err

[Yenchia Chen]

From: Eric Dumazet <edumazet@google.com>

syzbot caught another data-race in netlink when
setting sk->sk_err.

Annotate all of them for good measure.

BUG: KCSAN: data-race in netlink_recvmsg / netlink_recvmsg

write to 0xffff8881613bb220 of 4 bytes by task 28147 on cpu 0:
netlink_recvmsg+0x448/0x780 net/netlink/af_netlink.c:1994
sock_recvmsg_nosec net/socket.c:1027 [inline]
sock_recvmsg net/socket.c:1049 [inline]
__sys_recvfrom+0x1f4/0x2e0 net/socket.c:2229
__do_sys_recvfrom net/socket.c:2247 [inline]
__se_sys_recvfrom net/socket.c:2243 [inline]
__x64_sys_recvfrom+0x78/0x90 net/socket.c:2243
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffff8881613bb220 of 4 bytes by task 28146 on cpu 1:
netlink_recvmsg+0x448/0x780 net/netlink/af_netlink.c:1994
sock_recvmsg_nosec net/socket.c:1027 [inline]
sock_recvmsg net/socket.c:1049 [inline]
__sys_recvfrom+0x1f4/0x2e0 net/socket.c:2229
__do_sys_recvfrom net/socket.c:2247 [inline]
__se_sys_recvfrom net/socket.c:2243 [inline]
__x64_sys_recvfrom+0x78/0x90 net/socket.c:2243
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000000 -> 0x00000016

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 28146 Comm: syz-executor.0 Not tainted 6.6.0-rc3-syzkaller-00055-g9ed22ae6be81 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20231003183455.3410550-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: yenchia.chen <yenchia.chen@mediatek.com>
---
 net/netlink/af_netlink.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 56ba8a6396ca..216445dd44db 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -352,7 +352,7 @@ static void netlink_overrun(struct sock *sk)
 	if (!(nlk->flags & NETLINK_F_RECV_NO_ENOBUFS)) {
 		if (!test_and_set_bit(NETLINK_S_CONGESTED,
 				      &nlk_sk(sk)->state)) {
-			sk->sk_err = ENOBUFS;
+			WRITE_ONCE(sk->sk_err, ENOBUFS);
 			sk_error_report(sk);
 		}
 	}
@@ -1591,7 +1591,7 @@ static int do_one_set_err(struct sock *sk, struct netlink_set_err_data *p)
 		goto out;
 	}
 
-	sk->sk_err = p->code;
+	WRITE_ONCE(sk->sk_err, p->code);
 	sk_error_report(sk);
 out:
 	return ret;
@@ -2006,7 +2006,7 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	    atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) {
 		ret = netlink_dump(sk);
 		if (ret) {
-			sk->sk_err = -ret;
+			WRITE_ONCE(sk->sk_err, -ret);
 			sk_error_report(sk);
 		}
 	}
@@ -2442,7 +2442,7 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 
 	skb = nlmsg_new(payload + tlvlen, GFP_KERNEL);
 	if (!skb) {
-		NETLINK_CB(in_skb).sk->sk_err = ENOBUFS;
+		WRITE_ONCE(NETLINK_CB(in_skb).sk->sk_err, ENOBUFS);
 		sk_error_report(NETLINK_CB(in_skb).sk);
 		return;
 	}
-- 
2.18.0


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Re: [PATCH 5.15 1/2] netlink: annotate lockless accesses to nlk->max_recvmsg_len

[Carlos Llamas]

On Wed, May 15, 2024 at 03:36:37PM +0800, Yenchia Chen wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> syzbot reported a data-race in data-race in netlink_recvmsg() [1]
> 
> Indeed, netlink_recvmsg() can be run concurrently,
> and netlink_dump() also needs protection.
> 
> [1]
> BUG: KCSAN: data-race in netlink_recvmsg / netlink_recvmsg
> 
> read to 0xffff888141840b38 of 8 bytes by task 23057 on cpu 0:
> netlink_recvmsg+0xea/0x730 net/netlink/af_netlink.c:1988
> sock_recvmsg_nosec net/socket.c:1017 [inline]
> sock_recvmsg net/socket.c:1038 [inline]
> __sys_recvfrom+0x1ee/0x2e0 net/socket.c:2194
> __do_sys_recvfrom net/socket.c:2212 [inline]
> __se_sys_recvfrom net/socket.c:2208 [inline]
> __x64_sys_recvfrom+0x78/0x90 net/socket.c:2208
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> write to 0xffff888141840b38 of 8 bytes by task 23037 on cpu 1:
> netlink_recvmsg+0x114/0x730 net/netlink/af_netlink.c:1989
> sock_recvmsg_nosec net/socket.c:1017 [inline]
> sock_recvmsg net/socket.c:1038 [inline]
> ____sys_recvmsg+0x156/0x310 net/socket.c:2720
> ___sys_recvmsg net/socket.c:2762 [inline]
> do_recvmmsg+0x2e5/0x710 net/socket.c:2856
> __sys_recvmmsg net/socket.c:2935 [inline]
> __do_sys_recvmmsg net/socket.c:2958 [inline]
> __se_sys_recvmmsg net/socket.c:2951 [inline]
> __x64_sys_recvmmsg+0xe2/0x160 net/socket.c:2951
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> value changed: 0x0000000000000000 -> 0x0000000000001000
> 
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 1 PID: 23037 Comm: syz-executor.2 Not tainted 6.3.0-rc4-syzkaller-00195-g5a57b48fdfcb #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
> 
> Fixes: 9063e21fb026 ("netlink: autosize skb lengthes")
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reviewed-by: Simon Horman <simon.horman@corigine.com>
> Link: https://lore.kernel.org/r/20230403214643.768555-1-edumazet@google.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: yenchia.chen <yenchia.chen@mediatek.com>
> ---

The conflict resolution looks good to me, thanks!

Reviewed-by: Carlos Llamas <cmllamas@google.com>

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Re: [PATCH 5.15 2/2] netlink: annotate data-races around sk->sk_err

[Carlos Llamas]

On Wed, May 15, 2024 at 03:36:38PM +0800, Yenchia Chen wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> syzbot caught another data-race in netlink when
> setting sk->sk_err.
> 
> Annotate all of them for good measure.
> 
> BUG: KCSAN: data-race in netlink_recvmsg / netlink_recvmsg
> 
> write to 0xffff8881613bb220 of 4 bytes by task 28147 on cpu 0:
> netlink_recvmsg+0x448/0x780 net/netlink/af_netlink.c:1994
> sock_recvmsg_nosec net/socket.c:1027 [inline]
> sock_recvmsg net/socket.c:1049 [inline]
> __sys_recvfrom+0x1f4/0x2e0 net/socket.c:2229
> __do_sys_recvfrom net/socket.c:2247 [inline]
> __se_sys_recvfrom net/socket.c:2243 [inline]
> __x64_sys_recvfrom+0x78/0x90 net/socket.c:2243
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> write to 0xffff8881613bb220 of 4 bytes by task 28146 on cpu 1:
> netlink_recvmsg+0x448/0x780 net/netlink/af_netlink.c:1994
> sock_recvmsg_nosec net/socket.c:1027 [inline]
> sock_recvmsg net/socket.c:1049 [inline]
> __sys_recvfrom+0x1f4/0x2e0 net/socket.c:2229
> __do_sys_recvfrom net/socket.c:2247 [inline]
> __se_sys_recvfrom net/socket.c:2243 [inline]
> __x64_sys_recvfrom+0x78/0x90 net/socket.c:2243
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> value changed: 0x00000000 -> 0x00000016
> 
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 1 PID: 28146 Comm: syz-executor.0 Not tainted 6.6.0-rc3-syzkaller-00055-g9ed22ae6be81 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Reviewed-by: Simon Horman <horms@kernel.org>
> Link: https://lore.kernel.org/r/20231003183455.3410550-1-edumazet@google.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: yenchia.chen <yenchia.chen@mediatek.com>
> ---

The conflict resolution looks good to me, thanks!

Reviewed-by: Carlos Llamas <cmllamas@google.com>

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Re: [PATCH 5.15 0/2] netlink, fix issues caught by syzbot

[Greg KH]

On Wed, May 15, 2024 at 03:36:36PM +0800, Yenchia Chen wrote:
> From: "yenchia.chen" <yenchia.chen@mediatek.com>
> 
> Hi,
> 
> We think 5.15.y could pick these commits.
> 
> Below is the mainline commit:
> 
> netlink: annotate lockless accesses to nlk->max_recvmsg_len
> [ Upstream commit a1865f2e7d10dde00d35a2122b38d2e469ae67ed ]
> 
> netlink: annotate data-races around sk->sk_err
> [ Upstream commit d0f95894fda7d4f895b29c1097f92d7fee278cb2 ]
> 
> Eric Dumazet (2):
>   netlink: annotate lockless accesses to nlk->max_recvmsg_len
>   netlink: annotate data-races around sk->sk_err
> 
>  net/netlink/af_netlink.c | 23 +++++++++++++----------
>  1 file changed, 13 insertions(+), 10 deletions(-)
> 
> -- 
> 2.18.0
> 
> 

All now queued up, thanks.

greg k-h

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