Systemd is causing mislabeled devices to be created and then attempting to read them.

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On 07/28/2010 05:57 AM, Kay Sievers wrote:
> On Wed, Jul 28, 2010 at 11:43, Lennart Poettering
> <lennart@poettering.net> wrote:
>> On Mon, 26.07.10 16:42, Daniel J Walsh (dwalsh@redhat.com) wrote:
>>> tcontext=system_u:object_r:device_t:s0 tclass=chr_file
>>> type=1400 audit(1280174589.476:7): avc:  denied  { read } for  pid=1
>>> comm="systemd" name="autofs" dev=devtmpfs ino=9482
>>> scontext=system_u:system_r:init_t:s0
>>> tcontext=system_u:object_r:device_t:s0 tclass=chr_file
>>> type=1400 audit(1280174589.476:8): avc:  denied  { read } for  pid=1
>>> comm="systemd" name="autofs" dev=devtmpfs ino=9482
>>> scontext=system_u:system_r:init_t:s0
>>> tcontext=system_u:object_r:device_t:s0 tclass=chr_file
>>>
>>> Lennart, we talked about this earlier.  I think this is caused by the
>>> modprobe calls to create /dev/autofs.  Since udev is not created at the
>>> point that init loads the kernel modules, the devices get created with
>>> the wrong label.  Once udev starts the labels get fixed.
>>>
>>> I can allow init_t to read device_t chr_files.
>>
>> Hmm, I think a cleaner fix would be to make systemd relabel this device
>> properly before accessing it? Given that this is only one device this
>> should not be a problem for us to maintain, I think? How would the
>> fixing of the label work? Would we have to spawn restorecon for this, or
>> can we actually do this in C without too much work?
>
> I guess we can just do what udev is doing, and call setfilecon(), with
> a context of an earlier matchpathcon().
>
> Kay
> _______________________________________________
> systemd-devel mailing list
> systemd-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/systemd-devel

Here is the updated patch with a fix for the labeling of /dev/autofs
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1 files changed, 13 insertions, 81 deletions

diff --git a/src/socket.c b/src/socket.c
index 2da3215a3d..2a5270f336 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -27,7 +27,6 @@
 #include <sys/epoll.h>
 #include <signal.h>
 #include <arpa/inet.h>
-#include <selinux/selinux.h>
 
 #include "unit.h"
 #include "socket.h"
@@ -653,89 +652,25 @@ static void socket_apply_fifo_options(Socket *s, int fd) {
                         log_warning("F_SETPIPE_SZ: %m");
 }
 
-static int selinux_getconfromexe(
-                const char *exe,
-                security_context_t *newcon) {
-
-        security_context_t mycon = NULL, fcon = NULL;
-        security_class_t sclass;
-        int r = 0;
-
-        r = getcon(&mycon);
-        if (r < 0)
-                goto fail;
-
-        r = getfilecon(exe, &fcon);
-        if (r < 0)
-                goto fail;
-
-        sclass = string_to_security_class("process");
-        r = security_compute_create(mycon, fcon, sclass, newcon);
-
-fail:
-        if (r < 0)
-                r = -errno;
-
-        freecon(mycon);
-        freecon(fcon);
-        return r;
-}
-
-static int selinux_getfileconfrompath(
-                const security_context_t scon,
-                const char *path,
-                const char *class,
-                security_context_t *fcon) {
-
-        security_context_t dir_con = NULL;
-        security_class_t sclass;
-        int r = 0;
-
-        r = getfilecon(path, &dir_con);
-        if (r >= 0) {
-                r = -1;
-                if ((sclass = string_to_security_class(class)) != 0)
-                        r = security_compute_create(scon, dir_con, sclass, fcon);
-        }
-        if (r < 0)
-                r = -errno;
-
-        freecon(dir_con);
-        return r;
-}
 
 static int fifo_address_create(
                 const char *path,
                 mode_t directory_mode,
                 mode_t socket_mode,
-                security_context_t scon,
+                const char *label,
                 int *_fd) {
 
         int fd = -1, r = 0;
         struct stat st;
         mode_t old_mask;
-        security_context_t filecon = NULL;
 
         assert(path);
         assert(_fd);
 
         mkdir_parents(path, directory_mode);
 
-        if (scon) {
-                if (scon && ((r = selinux_getfileconfrompath(scon, path, "fifo_file", &filecon)) == 0)) {
-                        r = setfscreatecon(filecon);
-
-                        if (r < 0) {
-                                log_error("Failed to set SELinux file context (%s) on %s: %m", scon, path);
-                                r = -errno;
-                        }
-
-                        freecon(filecon);
-                }
-
-                if (r < 0  && security_getenforce() == 1)
-                        goto fail;
-        }
+        if ((r = label_fifofile_set(label, path)) < 0)
+                goto fail;
 
         /* Enforce the right access mode for the fifo */
         old_mask = umask(~ socket_mode);
@@ -756,7 +691,7 @@ static int fifo_address_create(
                 goto fail;
         }
 
-        setfscreatecon(NULL);
+        label_file_clear();
 
         if (fstat(fd, &st) < 0) {
                 r = -errno;
@@ -776,7 +711,8 @@ static int fifo_address_create(
         return 0;
 
 fail:
-        setfscreatecon(NULL);
+        label_file_clear();
+
         if (fd >= 0)
                 close_nointr_nofail(fd);
 
@@ -786,20 +722,16 @@ fail:
 static int socket_open_fds(Socket *s) {
         SocketPort *p;
         int r;
-        security_context_t scon = NULL;
+        char *label = NULL;
 
         assert(s);
 
         if ((r = socket_instantiate_service(s)) < 0)
                 return r;
 
-        if (selinux_getconfromexe(s->service->exec_command[SERVICE_EXEC_START]->path, &scon) < 0) {
-                log_error("Failed to get SELinux exec context for %s \n", s->service->exec_command[SERVICE_EXEC_START]->path);
-                if (security_getenforce() == 1)
-                        return -errno;
-        }
+        if ((r = label_get_socket_label_from_exe(s->service->exec_command[SERVICE_EXEC_START]->path, &label)) < 0)
+                return r;
 
-        log_debug("SELinux Socket context for %s set to %s\n", s->service->exec_command[SERVICE_EXEC_START]->path, scon);
         LIST_FOREACH(port, p, s->ports) {
 
                 if (p->fd >= 0)
@@ -815,7 +747,7 @@ static int socket_open_fds(Socket *s) {
                                              s->free_bind,
                                              s->directory_mode,
                                              s->socket_mode,
-                                             scon,
+                                             label,
                                              &p->fd)) < 0)
                                 goto rollback;
 
@@ -827,7 +759,7 @@ static int socket_open_fds(Socket *s) {
                                              p->path,
                                              s->directory_mode,
                                              s->socket_mode,
-                                             scon,
+                                             label,
                                              &p->fd)) < 0)
                                 goto rollback;
 
@@ -837,12 +769,12 @@ static int socket_open_fds(Socket *s) {
                         assert_not_reached("Unknown port type");
         }
 
-        freecon(scon);
+        label_free(label);
         return 0;
 
 rollback:
         socket_close_fds(s);
-        freecon(scon);
+        label_free(label);
         return r;
 }