From: Eric Biggers <ebiggers@kernel.org>
To: netdev@vger.kernel.org, "David S . Miller" <davem@davemloft.net>
Cc: linux-kernel@vger.kernel.org, Mao Wenan <maowenan@huawei.com>,
Cong Wang <xiyou.wangcong@gmail.com>,
Lorenzo Colitti <lorenzo@google.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Al Viro <viro@zeniv.linux.org.uk>,
Eric Biggers <ebiggers@kernel.org>
Subject: [PATCH net] net: socket: set sock->sk to NULL after calling proto_ops::release()
Date: Thu, 21 Feb 2019 14:13:56 -0800 [thread overview]
Message-ID: <20190221221356.173485-1-ebiggers@kernel.org> (raw)
From: Eric Biggers <ebiggers@google.com>
Commit 9060cb719e61 ("net: crypto set sk to NULL when af_alg_release.")
fixed a use-after-free in sockfs_setattr() when an AF_ALG socket is
closed concurrently with fchownat(). However, it ignored that many
other proto_ops::release() methods don't set sock->sk to NULL and
therefore allow the same use-after-free:
- base_sock_release
- bnep_sock_release
- cmtp_sock_release
- data_sock_release
- dn_release
- hci_sock_release
- hidp_sock_release
- iucv_sock_release
- l2cap_sock_release
- llcp_sock_release
- llc_ui_release
- rawsock_release
- rfcomm_sock_release
- sco_sock_release
- svc_release
- vcc_release
- x25_release
Rather than fixing all these and relying on every socket type to get
this right forever, just make __sock_release() set sock->sk to NULL
itself after calling proto_ops::release().
Reproducer that produces the KASAN splat when any of these socket types
are configured into the kernel:
#include <pthread.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <unistd.h>
pthread_t t;
volatile int fd;
void *close_thread(void *arg)
{
for (;;) {
usleep(rand() % 100);
close(fd);
}
}
int main()
{
pthread_create(&t, NULL, close_thread, NULL);
for (;;) {
fd = socket(rand() % 50, rand() % 11, 0);
fchownat(fd, "", 1000, 1000, 0x1000);
close(fd);
}
}
Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.")
Cc: <stable@vger.kernel.org> # v4.10+
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
NOTE: I am not an expert in the networking code, so please carefully
check that I haven't missed some reason why this simple fix won't do.
net/socket.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/socket.c b/net/socket.c
index d80d87a395ea..320f51b22b19 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -577,6 +577,7 @@ static void __sock_release(struct socket *sock, struct inode *inode)
if (inode)
inode_lock(inode);
sock->ops->release(sock);
+ sock->sk = NULL;
if (inode)
inode_unlock(inode);
sock->ops = NULL;
--
2.21.0.rc0.258.g878e2cd30e-goog
next reply other threads:[~2019-02-21 22:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-21 22:13 Eric Biggers [this message]
2019-02-22 2:51 ` [PATCH net] net: socket: set sock->sk to NULL after calling proto_ops::release() Al Viro
2019-02-22 17:45 ` Eric Dumazet
2019-02-22 17:57 ` Eric Biggers
2019-02-22 18:25 ` Eric Dumazet
2019-02-22 19:08 ` Al Viro
2019-02-22 18:05 ` Cong Wang
2019-02-25 18:41 ` David Miller
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