Use shm_open instead of mkstemp

shm_open is more reliable because it does not require
a writeable filesystem folder, unlike mkstemp.

(cherry picked from commit e2bc8866f46701e9c825ad7fa5baac02b2e4898f)

1 files changed, 31 insertions, 35 deletions

diff --git a/client/pool-buffer.c b/client/pool-buffer.c
index ea31edd3..3546b897 100644
--- a/client/pool-buffer.c
+++ b/client/pool-buffer.c
@@ -1,50 +1,43 @@
 #define _POSIX_C_SOURCE 200809
 #include <assert.h>
 #include <cairo.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <pango/pangocairo.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/mman.h>
+#include <time.h>
 #include <unistd.h>
 #include <wayland-client.h>
 #include "config.h"
 #include "pool-buffer.h"
 #include "util.h"
 
-static int create_pool_file(size_t size, char **name) {
-        static const char template[] = "sway-client-XXXXXX";
-        const char *path = getenv("XDG_RUNTIME_DIR");
-        if (path == NULL) {
-                fprintf(stderr, "XDG_RUNTIME_DIR is not set\n");
-                return -1;
-        }
-
-        size_t name_size = strlen(template) + 1 + strlen(path) + 1;
-        *name = malloc(name_size);
-        if (*name == NULL) {
-                fprintf(stderr, "allocation failed\n");
-                return -1;
-        }
-        snprintf(*name, name_size, "%s/%s", path, template);
-
-        int fd = mkstemp(*name);
-        if (fd < 0) {
-                return -1;
-        }
-
-        if (!sway_set_cloexec(fd, true)) {
-                close(fd);
-                return -1;
-        }
+static int anonymous_shm_open(void) {
+        int retries = 100;
+
+        do {
+                // try a probably-unique name
+                struct timespec ts;
+                clock_gettime(CLOCK_MONOTONIC, &ts);
+                pid_t pid = getpid();
+                char name[50];
+                snprintf(name, sizeof(name), "/sway-%x-%x",
+                        (unsigned int)pid, (unsigned int)ts.tv_nsec);
+
+                // shm_open guarantees that O_CLOEXEC is set
+                int fd = shm_open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
+                if (fd >= 0) {
+                        shm_unlink(name);
+                        return fd;
+                }
 
-        if (ftruncate(fd, size) < 0) {
-                close(fd);
-                return -1;
-        }
+                --retries;
+        } while (retries > 0 && errno == EEXIST);
 
-        return fd;
+        return -1;
 }
 
 static void buffer_release(void *data, struct wl_buffer *wl_buffer) {
@@ -62,17 +55,20 @@ static struct pool_buffer *create_buffer(struct wl_shm *shm,
         uint32_t stride = width * 4;
         size_t size = stride * height;
 
-        char *name;
-        int fd = create_pool_file(size, &name);
-        assert(fd != -1);
+        int fd = anonymous_shm_open();
+        if (fd == -1) {
+                return NULL;
+        }
+        if (ftruncate(fd, size) < 0) {
+                close(fd);
+                return NULL;
+        }
         void *data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
         struct wl_shm_pool *pool = wl_shm_create_pool(shm, fd, size);
         buf->buffer = wl_shm_pool_create_buffer(pool, 0,
                         width, height, stride, format);
         wl_shm_pool_destroy(pool);
         close(fd);
-        unlink(name);
-        free(name);
 
         buf->size = size;
         buf->width = width;