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net/scm: Regularize compat handling of scm_detach_fds()

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Duplicate the cleanups from commit 2618d530dd ("net/scm: cleanup
scm_detach_fds") into the compat code.

Replace open-coded __receive_sock() with a call to the helper.

Move the check added in commit 1f466e1f15 ("net: cleanly handle kernel
vs user buffers for ->msg_control") to before the compat call, even
though it should be impossible for an in-kernel call to also be compat.

Correct the int "flags" argument to unsigned int to match fd_install()
and similar APIs.

Regularize any remaining differences, including a whitespace issue,
a checkpatch warning, and add the check from commit 6900317f5e ("net,
scm: fix PaX detected msg_controllen overflow in scm_detach_fds") which
fixed an overflow unique to 64-bit. To avoid confusion when comparing
the compat handler to the native handler, just include the same check
in the compat handler.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2020-06-09 16:11:29 -07:00
parent 4969f8a073
commit c0029de509
3 changed files with 37 additions and 47 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

1
include/net/scm.h
View file

@ -37,6 +37,7 @@ struct scm_cookie {
#endif
};
int __scm_install_fd(struct file *file, int __user *ufd, unsigned int o_flags);
void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm);
void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm);
int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm);

56
net/compat.c
View file

@ -281,40 +281,31 @@ int put_cmsg_compat(struct msghdr *kmsg, int level, int type, int len, void *dat
return 0;
}
void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
static int scm_max_fds_compat(struct msghdr *msg)
{
struct compat_cmsghdr __user *cm = (struct compat_cmsghdr __user *) kmsg->msg_control;
int fdmax = (kmsg->msg_controllen - sizeof(struct compat_cmsghdr)) / sizeof(int);
int fdnum = scm->fp->count;
struct file **fp = scm->fp->fp;
int __user *cmfptr;
if (msg->msg_controllen <= sizeof(struct compat_cmsghdr))
return 0;
return (msg->msg_controllen - sizeof(struct compat_cmsghdr)) / sizeof(int);
}
void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm)
{
struct compat_cmsghdr __user *cm =
(struct compat_cmsghdr __user *)msg->msg_control;
unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0;
int fdmax = min_t(int, scm_max_fds_compat(msg), scm->fp->count);
int __user *cmsg_data = CMSG_USER_DATA(cm);
int err = 0, i;
if (fdnum < fdmax)
fdmax = fdnum;
for (i = 0, cmfptr = (int __user *) CMSG_COMPAT_DATA(cm); i < fdmax; i++, cmfptr++) {
int new_fd;
err = security_file_receive(fp[i]);
for (i = 0; i < fdmax; i++) {
err = __scm_install_fd(scm->fp->fp[i], cmsg_data + i, o_flags);
if (err)
break;
err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & kmsg->msg_flags
? O_CLOEXEC : 0);
if (err < 0)
break;
new_fd = err;
err = put_user(new_fd, cmfptr);
if (err) {
put_unused_fd(new_fd);
break;
}
/* Bump the usage count and install the file. */
__receive_sock(fp[i]);
fd_install(new_fd, get_file(fp[i]));
}
if (i > 0) {
int cmlen = CMSG_COMPAT_LEN(i * sizeof(int));
err = put_user(SOL_SOCKET, &cm->cmsg_level);
if (!err)
err = put_user(SCM_RIGHTS, &cm->cmsg_type);
@ -322,16 +313,19 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
err = put_user(cmlen, &cm->cmsg_len);
if (!err) {
cmlen = CMSG_COMPAT_SPACE(i * sizeof(int));
kmsg->msg_control += cmlen;
kmsg->msg_controllen -= cmlen;
if (msg->msg_controllen < cmlen)
cmlen = msg->msg_controllen;
msg->msg_control += cmlen;
msg->msg_controllen -= cmlen;
}
}
if (i < fdnum)
kmsg->msg_flags |= MSG_CTRUNC;
if (i < scm->fp->count || (scm->fp->count && fdmax <= 0))
msg->msg_flags |= MSG_CTRUNC;
/*
* All of the files that fit in the message have had their
* usage counts incremented, so we just free the list.
* All of the files that fit in the message have had their usage counts
* incremented, so we just free the list.
*/
__scm_destroy(scm);
}

27
net/core/scm.c
View file

@ -280,9 +280,8 @@ void put_cmsg_scm_timestamping(struct msghdr *msg, struct scm_timestamping_inter
}
EXPORT_SYMBOL(put_cmsg_scm_timestamping);
static int __scm_install_fd(struct file *file, int __user *ufd, int o_flags)
int __scm_install_fd(struct file *file, int __user *ufd, unsigned int o_flags)
{
struct socket *sock;
int new_fd;
int error;
@ -300,12 +299,8 @@ static int __scm_install_fd(struct file *file, int __user *ufd, int o_flags)
return error;
}
/* Bump the usage count and install the file. */
sock = sock_from_file(file, &error);
if (sock) {
sock_update_netprioidx(&sock->sk->sk_cgrp_data);
sock_update_classid(&sock->sk->sk_cgrp_data);
}
/* Bump the sock usage counts, if any. */
__receive_sock(file);
fd_install(new_fd, get_file(file));
return 0;
}
@ -319,29 +314,29 @@ static int scm_max_fds(struct msghdr *msg)
void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
{
struct cmsghdr __user *cm
= (__force struct cmsghdr __user*)msg->msg_control;
int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0;
struct cmsghdr __user *cm =
(__force struct cmsghdr __user *)msg->msg_control;
unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0;
int fdmax = min_t(int, scm_max_fds(msg), scm->fp->count);
int __user *cmsg_data = CMSG_USER_DATA(cm);
int err = 0, i;
/* no use for FD passing from kernel space callers */
if (WARN_ON_ONCE(!msg->msg_control_is_user))
return;
if (msg->msg_flags & MSG_CMSG_COMPAT) {
scm_detach_fds_compat(msg, scm);
return;
}
/* no use for FD passing from kernel space callers */
if (WARN_ON_ONCE(!msg->msg_control_is_user))
return;
for (i = 0; i < fdmax; i++) {
err = __scm_install_fd(scm->fp->fp[i], cmsg_data + i, o_flags);
if (err)
break;
}
if (i > 0) {
if (i > 0) {
int cmlen = CMSG_LEN(i * sizeof(int));
err = put_user(SOL_SOCKET, &cm->cmsg_level);