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Message-Id: <20200709182642.1773477-4-keescook@chromium.org>
Date: Thu, 9 Jul 2020 11:26:36 -0700
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
Christian Brauner <christian.brauner@...ntu.com>,
Sargun Dhillon <sargun@...gun.me>,
Christian Brauner <christian@...uner.io>,
Tycho Andersen <tycho@...ho.ws>,
David Laight <David.Laight@...LAB.COM>,
Christoph Hellwig <hch@....de>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Aleksa Sarai <cyphar@...har.com>,
Matt Denton <mpdenton@...gle.com>,
Jann Horn <jannh@...gle.com>, Chris Palmer <palmer@...gle.com>,
Robert Sesek <rsesek@...gle.com>,
Giuseppe Scrivano <gscrivan@...hat.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Andy Lutomirski <luto@...capital.net>,
Will Drewry <wad@...omium.org>, Shuah Khan <shuah@...nel.org>,
netdev@...r.kernel.org, containers@...ts.linux-foundation.org,
linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kselftest@...r.kernel.org
Subject: [PATCH v7 3/9] net/scm: Regularize compat handling of scm_detach_fds()
Duplicate the cleanups from commit 2618d530dd8b ("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 1f466e1f15cf ("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 6900317f5eff ("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.
Acked-by: Christian Brauner <christian.brauner@...ntu.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
include/net/scm.h | 1 +
net/compat.c | 56 +++++++++++++++++++++--------------------------
net/core/scm.c | 27 ++++++++++-------------
3 files changed, 37 insertions(+), 47 deletions(-)
diff --git a/include/net/scm.h b/include/net/scm.h
index 1ce365f4c256..581a94d6c613 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -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);
diff --git a/net/compat.c b/net/compat.c
index 2937b816107d..27d477fdcaa0 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -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;
- int err = 0, i;
+ if (msg->msg_controllen <= sizeof(struct compat_cmsghdr))
+ return 0;
+ return (msg->msg_controllen - sizeof(struct compat_cmsghdr)) / sizeof(int);
+}
- if (fdnum < fdmax)
- fdmax = fdnum;
+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;
- 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);
}
diff --git a/net/core/scm.c b/net/core/scm.c
index 875df1c2989d..44f03213dcab 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -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);
--
2.25.1
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