From c0029de50982c1fb215330a5f9d433cec0cfd8cc Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 9 Jun 2020 16:11:29 -0700 Subject: 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. Cc: Christoph Hellwig Cc: Sargun Dhillon Cc: Jakub Kicinski Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Acked-by: Christian Brauner Signed-off-by: Kees Cook --- net/compat.c | 56 +++++++++++++++++++++++++------------------------------- 1 file changed, 25 insertions(+), 31 deletions(-) (limited to 'net/compat.c') 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); } -- cgit