Fix: userspace probe accessors are not const-correct

[lttng-tools.git] / src / bin / lttng-sessiond / shm.c

diff --git a/src/bin/lttng-sessiond/shm.c b/src/bin/lttng-sessiond/shm.c
index b94f4eb6a7aae86aed5fc080689e3f755456c719..a6328d5f618fb4474d70b5d5966cf45d5ff4a121 100644 (file)
--- a/src/bin/lttng-sessiond/shm.c
+++ b/src/bin/lttng-sessiond/shm.c
@@ -16,7 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#define _GNU_SOURCE
+#define _LGPL_SOURCE
 #include <fcntl.h>
 #include <limits.h>
 #include <sys/mman.h>
@@ -48,40 +48,17 @@ static int get_wait_shm(char *shm_path, size_t mmap_size, int global)
        /* Default permissions */
        mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP;
 
-       /* Change owner of the shm path */
+       /*
+        * Change owner of the shm path.
+        */
        if (global) {
-               ret = chown(shm_path, 0, 0);
-               if (ret < 0) {
-                       if (errno != ENOENT) {
-                               PERROR("chown wait shm");
-                               goto error;
-                       }
-               }
-
                /*
-                * If global session daemon, any application can register so the shm
-                * needs to be set in read-only mode for others.
+                * If global session daemon, any application can
+                * register. Make it initially writeable so applications
+                * registering concurrently can do ftruncate() by
+                * themselves.
                 */
-               mode |= S_IROTH;
-       } else {
-               ret = chown(shm_path, getuid(), getgid());
-               if (ret < 0) {
-                       if (errno != ENOENT) {
-                               PERROR("chown wait shm");
-                               goto error;
-                       }
-               }
-       }
-
-       /*
-        * Set permissions to the shm even if we did not create the shm.
-        */
-       ret = chmod(shm_path, mode);
-       if (ret < 0) {
-               if (errno != ENOENT) {
-                       PERROR("chmod wait shm");
-                       goto error;
-               }
+               mode |= S_IROTH | S_IWOTH;
        }
 
        /*
@@ -107,13 +84,32 @@ static int get_wait_shm(char *shm_path, size_t mmap_size, int global)
        }
 
 #ifndef __FreeBSD__
-       ret = fchmod(wait_shm_fd, mode);
-       if (ret < 0) {
-               PERROR("fchmod");
-               exit(EXIT_FAILURE);
+       if (global) {
+               ret = fchown(wait_shm_fd, 0, 0);
+               if (ret < 0) {
+                       PERROR("fchown");
+                       exit(EXIT_FAILURE);
+               }
+               /*
+                * If global session daemon, any application can
+                * register so the shm needs to be set in read-only mode
+                * for others.
+                */
+               mode &= ~S_IWOTH;
+               ret = fchmod(wait_shm_fd, mode);
+               if (ret < 0) {
+                       PERROR("fchmod");
+                       exit(EXIT_FAILURE);
+               }
+       } else {
+               ret = fchown(wait_shm_fd, getuid(), getgid());
+               if (ret < 0) {
+                       PERROR("fchown");
+                       exit(EXIT_FAILURE);
+               }
        }
 #else
-#warning "FreeBSD does not support setting file mode on shm FD. Remember that for secure use, lttng-sessiond should be started before applications linked on lttng-ust."
+#warning "FreeBSD does not support setting file mode on shm FD."
 #endif
 
        DBG("Got the wait shm fd %d", wait_shm_fd);
@@ -136,12 +132,20 @@ error:
  */
 char *shm_ust_get_mmap(char *shm_path, int global)
 {
-       size_t mmap_size = sysconf(_SC_PAGE_SIZE);
+       size_t mmap_size;
        int wait_shm_fd, ret;
        char *wait_shm_mmap;
+       long sys_page_size;
 
        assert(shm_path);
 
+       sys_page_size = sysconf(_SC_PAGE_SIZE);
+       if (sys_page_size < 0) {
+               PERROR("sysconf PAGE_SIZE");
+               goto error;
+       }
+       mmap_size = sys_page_size;
+
        wait_shm_fd = get_wait_shm(shm_path, mmap_size, global);
        if (wait_shm_fd < 0) {
                goto error;