4.20-stable review patch. If anyone has any objections, please let me know.
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From: Eric Biggers ebiggers@google.com
[ Upstream commit ff7b11aa481f682e0e9711abfeb7d03f5cd612bf ]
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.") 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/socket.c | 1 + 1 file changed, 1 insertion(+)
--- a/net/socket.c +++ b/net/socket.c @@ -577,6 +577,7 @@ static void __sock_release(struct socket if (inode) inode_lock(inode); sock->ops->release(sock); + sock->sk = NULL; if (inode) inode_unlock(inode); sock->ops = NULL;