[PATCH 2/3] net/scm: cleanup scm_detach_fds

Christoph Hellwig
2020-05-11T11:59:49Z

Factor out two helpes to keep the code tidy.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
net/core/scm.c | 94 +++++++++++++++++++++++++++-----------------------
1 file changed, 51 insertions(+), 43 deletions(-)

diff --git a/net/core/scm.c b/net/core/scm.c
index abfdc85a64c1b..168b006a52ff9 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -277,78 +277,86 @@ 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)
+{
+ struct socket *sock;
+ int new_fd;
+ int error;
+
+ error = security_file_receive(file);
+ if (error)
+ return error;
+
+ new_fd = get_unused_fd_flags(o_flags);
+ if (new_fd < 0)
+ return new_fd;
+
+ error = put_user(new_fd, ufd);
+ if (error) {
+ put_unused_fd(new_fd);
+ 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);
+ }
+ fd_install(new_fd, get_file(file));
+ return error;
+}
+
+static int scm_max_fds(struct msghdr *msg)
+{
+ if (msg->msg_controllen <= sizeof(struct cmsghdr))
+ return 0;
+ return (msg->msg_controllen - sizeof(struct cmsghdr)) / sizeof(int);
+}
+
void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
{
struct cmsghdr __user *cm
= (__force struct cmsghdr __user*)msg->msg_control;
-
- int fdmax = 0;
- int fdnum = scm->fp->count;
- struct file **fp = scm->fp->fp;
- int __user *cmfptr;
+ 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;

- if (MSG_CMSG_COMPAT & msg->msg_flags) {
+ if (msg->msg_flags & MSG_CMSG_COMPAT) {
scm_detach_fds_compat(msg, scm);
return;
}

- if (msg->msg_controllen > sizeof(struct cmsghdr))
- fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
- / sizeof(int));
-
- if (fdnum < fdmax)
- fdmax = fdnum;
-
- for (i=0, cmfptr =(int __user *)CMSG_USER_DATA(cm); i<fdmax;
- i++, cmfptr++)
- {
- struct socket *sock;
- 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 & msg->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. */
- sock = sock_from_file(fp[i], &err);
- if (sock) {
- sock_update_netprioidx(&sock->sk->sk_cgrp_data);
- sock_update_classid(&sock->sk->sk_cgrp_data);
- }
- fd_install(new_fd, get_file(fp[i]));
}

- if (i > 0)
- {
- int cmlen = CMSG_LEN(i*sizeof(int));
+ if (i > 0) {
+ int cmlen = CMSG_LEN(i * sizeof(int));
+
err = put_user(SOL_SOCKET, &cm->cmsg_level);
if (!err)
err = put_user(SCM_RIGHTS, &cm->cmsg_type);
if (!err)
err = put_user(cmlen, &cm->cmsg_len);
if (!err) {
- cmlen = CMSG_SPACE(i*sizeof(int));
+ cmlen = CMSG_SPACE(i * sizeof(int));
if (msg->msg_controllen < cmlen)
cmlen = msg->msg_controllen;
msg->msg_control += cmlen;
msg->msg_controllen -= cmlen;
}
}
- if (i < fdnum || (fdnum && fdmax <= 0))
+
+ 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);
}
--
2.26.2