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[net] inet: annotate data race in inet_send_prepare() and inet_dgram_connect()

Message ID 20210609075945.3976469-1-eric.dumazet@gmail.com (mailing list archive)
State Accepted
Commit dcd01eeac14486b56a790f5cce9b823440ba5b34
Delegated to: Netdev Maintainers
Headers show
Series [net] inet: annotate data race in inet_send_prepare() and inet_dgram_connect() | expand

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netdev/cover_letter success Link
netdev/fixes_present fail Series targets non-next tree, but doesn't contain any Fixes tags
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for net
netdev/subject_prefix success Link
netdev/cc_maintainers warning 2 maintainers not CCed: yoshfuji@linux-ipv6.org dsahern@kernel.org
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 2 this patch: 2
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Link
netdev/checkpatch warning WARNING: Possible repeated word: 'Google' WARNING: data_race without comment
netdev/build_allmodconfig_warn success Errors and warnings before: 2 this patch: 2
netdev/header_inline success Link

Commit Message

Eric Dumazet June 9, 2021, 7:59 a.m. UTC 
From: Eric Dumazet <edumazet@google.com>

Both functions are known to be racy when reading inet_num
as we do not want to grab locks for the common case the socket
has been bound already. The race is resolved in inet_autobind()
by reading again inet_num under the socket lock.

syzbot reported:
BUG: KCSAN: data-race in inet_send_prepare / udp_lib_get_port

write to 0xffff88812cba150e of 2 bytes by task 24135 on cpu 0:
 udp_lib_get_port+0x4b2/0xe20 net/ipv4/udp.c:308
 udp_v6_get_port+0x5e/0x70 net/ipv6/udp.c:89
 inet_autobind net/ipv4/af_inet.c:183 [inline]
 inet_send_prepare+0xd0/0x210 net/ipv4/af_inet.c:807
 inet6_sendmsg+0x29/0x80 net/ipv6/af_inet6.c:639
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg net/socket.c:674 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2350
 ___sys_sendmsg net/socket.c:2404 [inline]
 __sys_sendmmsg+0x315/0x4b0 net/socket.c:2490
 __do_sys_sendmmsg net/socket.c:2519 [inline]
 __se_sys_sendmmsg net/socket.c:2516 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2516
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812cba150e of 2 bytes by task 24132 on cpu 1:
 inet_send_prepare+0x21/0x210 net/ipv4/af_inet.c:806
 inet6_sendmsg+0x29/0x80 net/ipv6/af_inet6.c:639
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg net/socket.c:674 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2350
 ___sys_sendmsg net/socket.c:2404 [inline]
 __sys_sendmmsg+0x315/0x4b0 net/socket.c:2490
 __do_sys_sendmmsg net/socket.c:2519 [inline]
 __se_sys_sendmmsg net/socket.c:2516 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2516
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000 -> 0x9db4

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 24132 Comm: syz-executor.2 Not tainted 5.13.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
---
 net/ipv4/af_inet.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

patchwork-bot+netdevbpf@kernel.org June 9, 2021, 9:10 p.m. UTC | #1 
Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Wed,  9 Jun 2021 00:59:45 -0700 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> Both functions are known to be racy when reading inet_num
> as we do not want to grab locks for the common case the socket
> has been bound already. The race is resolved in inet_autobind()
> by reading again inet_num under the socket lock.
> 
> [...]

Here is the summary with links:
  - [net] inet: annotate data race in inet_send_prepare() and inet_dgram_connect()
    https://git.kernel.org/netdev/net/c/dcd01eeac144

You are awesome, thank you!
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diff mbox series

Patch

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index f17870ee558bbaa043c10dc5b8a61a3fa1304880..2f94d221c00e9888d0f5f3738593fda811215cc6 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -575,7 +575,7 @@  int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr,
 			return err;
 	}
 
-	if (!inet_sk(sk)->inet_num && inet_autobind(sk))
+	if (data_race(!inet_sk(sk)->inet_num) && inet_autobind(sk))
 		return -EAGAIN;
 	return sk->sk_prot->connect(sk, uaddr, addr_len);
 }
@@ -803,7 +803,7 @@  int inet_send_prepare(struct sock *sk)
 	sock_rps_record_flow(sk);
 
 	/* We may need to bind the socket. */
-	if (!inet_sk(sk)->inet_num && !sk->sk_prot->no_autobind &&
+	if (data_race(!inet_sk(sk)->inet_num) && !sk->sk_prot->no_autobind &&
 	    inet_autobind(sk))
 		return -EAGAIN;