| Message ID | 20200706201720.3482959-2-keescook@chromium.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add seccomp notifier ioctl that enables adding fds | expand |
On Mon, Jul 06, 2020 at 01:17:14PM -0700, Kees Cook wrote: > Duplicate the cleanups from commit 2618d530dd8b ("net/scm: cleanup > scm_detach_fds") into the compat code. > > 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. > > Fixes: 48a87cc26c13 ("net: netprio: fd passed in SCM_RIGHTS datagram not set correctly") > Fixes: d84295067fc7 ("net: net_cls: fd passed in SCM_RIGHTS datagram not set correctly") > Signed-off-by: Kees Cook <keescook@chromium.org> > --- Thanks. Just a comment below. Acked-by: Christian Brauner <christian.brauner@ubuntu.com> > include/net/scm.h | 1 + > net/compat.c | 55 +++++++++++++++++++++-------------------------- > net/core/scm.c | 18 ++++++++-------- > 3 files changed, 35 insertions(+), 39 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 5e3041a2c37d..27d477fdcaa0 100644 > --- a/net/compat.c > +++ b/net/compat.c > @@ -281,39 +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); Just a note that SCM_RIGHTS fd-sending is limited to 253 (SCM_MAX_FD) fds so min_t should never ouput > SCM_MAX_FD here afaict. > + 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. */ > - 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); > @@ -321,16 +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)) I think fdmax can't be < 0 after your changes? scm_max_fds() guarantees that fdmax is always >= 0 and min_t() guarantees that fdmax <= scm->fp->count. So the check should technically be :) 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..6151678c73ed 100644 > --- a/net/core/scm.c > +++ b/net/core/scm.c > @@ -280,7 +280,7 @@ 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; > @@ -319,29 +319,29 @@ 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 >
On Tue, Jul 07, 2020 at 01:41:03PM +0200, Christian Brauner wrote: > On Mon, Jul 06, 2020 at 01:17:14PM -0700, Kees Cook wrote: > > Duplicate the cleanups from commit 2618d530dd8b ("net/scm: cleanup > > scm_detach_fds") into the compat code. > > > > 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. > > > > Fixes: 48a87cc26c13 ("net: netprio: fd passed in SCM_RIGHTS datagram not set correctly") > > Fixes: d84295067fc7 ("net: net_cls: fd passed in SCM_RIGHTS datagram not set correctly") > > Signed-off-by: Kees Cook <keescook@chromium.org> > > --- > > Thanks. Just a comment below. > Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Thanks! > > include/net/scm.h | 1 + > > net/compat.c | 55 +++++++++++++++++++++-------------------------- > > net/core/scm.c | 18 ++++++++-------- > > 3 files changed, 35 insertions(+), 39 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 5e3041a2c37d..27d477fdcaa0 100644 > > --- a/net/compat.c > > +++ b/net/compat.c > > @@ -281,39 +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); > > Just a note that SCM_RIGHTS fd-sending is limited to 253 (SCM_MAX_FD) > fds so min_t should never ouput > SCM_MAX_FD here afaict. > > > + 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. */ > > - 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); > > @@ -321,16 +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)) > > I think fdmax can't be < 0 after your changes? scm_max_fds() guarantees > that fdmax is always >= 0 and min_t() guarantees that fdmax <= scm->fp->count. > So the check should technically be :) You left our your suggestion! :) But, I think you mean "== 0" ? The check actually comes from the refactoring from commit 2618d530dd8b ("net/scm: cleanup scm_detach_fds") which I mostly copy/pasted into compat. However, fdmax is an int, and scm->fp->count is signed so it's possible fdmax is < 0 (but I don't think count can actually ever be < 0), but I don't want to refactor all the types just to fix this boundary condition. :)
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 5e3041a2c37d..27d477fdcaa0 100644 --- a/net/compat.c +++ b/net/compat.c @@ -281,39 +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. */ - 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); @@ -321,16 +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..6151678c73ed 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -280,7 +280,7 @@ 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; @@ -319,29 +319,29 @@ 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);
Duplicate the cleanups from commit 2618d530dd8b ("net/scm: cleanup scm_detach_fds") into the compat code. 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. Fixes: 48a87cc26c13 ("net: netprio: fd passed in SCM_RIGHTS datagram not set correctly") Fixes: d84295067fc7 ("net: net_cls: fd passed in SCM_RIGHTS datagram not set correctly") Signed-off-by: Kees Cook <keescook@chromium.org> --- include/net/scm.h | 1 + net/compat.c | 55 +++++++++++++++++++++-------------------------- net/core/scm.c | 18 ++++++++-------- 3 files changed, 35 insertions(+), 39 deletions(-)