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nfsd: fix double fget() bug in __write_ports_addfd()

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The bug here is that you cannot rely on getting the same socket
from multiple calls to fget() because userspace can influence
that.  This is a kind of double fetch bug.

The fix is to delete the svc_alien_sock() function and instead do
the checking inside the svc_addsock() function.

Fixes: 3064639423 ("nfsd: check passed socket's net matches NFSd superblock's one")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: NeilBrown <neilb@suse.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Dan Carpenter 2023-05-29 14:35:55 +03:00 committed by Chuck Lever
parent d53d70084d
commit c034203b6a
3 changed files with 10 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
fs/nfsd/nfsctl.c
View File

@ -690,16 +690,11 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net, const struct cred
if (err != 0 || fd < 0)
return -EINVAL;
if (svc_alien_sock(net, fd)) {
printk(KERN_ERR "%s: socket net is different to NFSd's one\n", __func__);
return -EINVAL;
}
err = nfsd_create_serv(net);
if (err != 0)
return err;
err = svc_addsock(nn->nfsd_serv, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);
err = svc_addsock(nn->nfsd_serv, net, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);
if (err >= 0 &&
!nn->nfsd_serv->sv_nrthreads && !xchg(&nn->keep_active, 1))

7
include/linux/sunrpc/svcsock.h
View File

@ -61,10 +61,9 @@ int svc_recv(struct svc_rqst *, long);
void svc_send(struct svc_rqst *rqstp);
void svc_drop(struct svc_rqst *);
void svc_sock_update_bufs(struct svc_serv *serv);
bool svc_alien_sock(struct net *net, int fd);
int svc_addsock(struct svc_serv *serv, const int fd,
char *name_return, const size_t len,
const struct cred *cred);
int svc_addsock(struct svc_serv *serv, struct net *net,
const int fd, char *name_return, const size_t len,
const struct cred *cred);
void svc_init_xprt_sock(void);
void svc_cleanup_xprt_sock(void);
struct svc_xprt *svc_sock_create(struct svc_serv *serv, int prot);

24
net/sunrpc/svcsock.c
View File

@ -1480,25 +1480,10 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
return svsk;
}
bool svc_alien_sock(struct net *net, int fd)
{
int err;
struct socket *sock = sockfd_lookup(fd, &err);
bool ret = false;
if (!sock)
goto out;
if (sock_net(sock->sk) != net)
ret = true;
sockfd_put(sock);
out:
return ret;
}
EXPORT_SYMBOL_GPL(svc_alien_sock);
/**
* svc_addsock - add a listener socket to an RPC service
* @serv: pointer to RPC service to which to add a new listener
* @net: caller's network namespace
* @fd: file descriptor of the new listener
* @name_return: pointer to buffer to fill in with name of listener
* @len: size of the buffer
@ -1508,8 +1493,8 @@ EXPORT_SYMBOL_GPL(svc_alien_sock);
* Name is terminated with '\n'. On error, returns a negative errno
* value.
*/
int svc_addsock(struct svc_serv *serv, const int fd, char *name_return,
const size_t len, const struct cred *cred)
int svc_addsock(struct svc_serv *serv, struct net *net, const int fd,
char *name_return, const size_t len, const struct cred *cred)
{
int err = 0;
struct socket *so = sockfd_lookup(fd, &err);
@ -1520,6 +1505,9 @@ int svc_addsock(struct svc_serv *serv, const int fd, char *name_return,
if (!so)
return err;
err = -EINVAL;
if (sock_net(so->sk) != net)
goto out;
err = -EAFNOSUPPORT;
if ((so->sk->sk_family != PF_INET) && (so->sk->sk_family != PF_INET6))
goto out;