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net: socket: set sock->sk to NULL after calling proto_ops::release()
Commit9060cb719e
("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:86741ec254
("net: core: Add a UID field to struct sock.") Signed-off-by: Eric Biggers <ebiggers@google.com> Acked-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -577,6 +577,7 @@ static void __sock_release(struct socket *sock, struct inode *inode)
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if (inode)
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if (inode)
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inode_lock(inode);
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inode_lock(inode);
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sock->ops->release(sock);
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sock->ops->release(sock);
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sock->sk = NULL;
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if (inode)
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if (inode)
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inode_unlock(inode);
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inode_unlock(inode);
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sock->ops = NULL;
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sock->ops = NULL;
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