X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;ds=sidebyside;f=libringbuffer%2Fshm.c;h=0d92572d7b5b6170d79ed7e457e115bba957b7ef;hb=5a61337d8b92f7419e58e5b46ffc4f75ac6269af;hp=e1dd56f91d0b06afb293a9d8bd601fc158e72845;hpb=dc613eb9d0c449f3e988af66b173abefa4b22233;p=lttng-ust.git

diff --git a/libringbuffer/shm.c b/libringbuffer/shm.c
index e1dd56f9..0d92572d 100644
--- a/libringbuffer/shm.c
+++ b/libringbuffer/shm.c
@@ -13,6 +13,9 @@
 #include <sys/stat.h>	/* For mode constants */
 #include <fcntl.h>	/* For O_* constants */
 #include <assert.h>
+#include <stdio.h>
+#include <signal.h>
+#include <dirent.h>
 #include <ust/align.h>
 
 struct shm_object_table *shm_object_table_create(size_t max_nb_obj)
@@ -28,9 +31,11 @@ struct shm_object_table *shm_object_table_create(size_t max_nb_obj)
 struct shm_object *shm_object_table_append(struct shm_object_table *table,
 					   size_t memory_map_size)
 {
-	int shmfd, waitfd[2], ret, i;
+	int shmfd, waitfd[2], ret, i, sigblocked = 0;
 	struct shm_object *obj;
 	char *memory_map;
+	char tmp_name[NAME_MAX] = "ust-shm-tmp-XXXXXX";
+	sigset_t all_sigs, orig_sigs;
 
 	if (table->allocated_len >= table->size)
 		return NULL;
@@ -59,6 +64,19 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
 
 	/* shm_fd: create shm */
 
+	/*
+	 * Theoretically, we could leak a shm if the application crashes
+	 * between open and unlink. Disable signals on this thread for
+	 * increased safety against this scenario.
+	 */
+	sigfillset(&all_sigs);
+	ret = pthread_sigmask(SIG_BLOCK, &all_sigs, &orig_sigs);
+	if (ret == -1) {
+		PERROR("pthread_sigmask");
+		goto error_pthread_sigmask;
+	}
+	sigblocked = 1;
+
 	/*
 	 * Allocate shm, and immediately unlink its shm oject, keeping
 	 * only the file descriptor as a reference to the object. If it
@@ -69,17 +87,32 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
 	 * the process (POSIX leaves this implementation-defined).
 	 */
 	do {
-		shmfd = shm_open("ust-shm-tmp",
+		/*
+		 * Using mktemp filename with O_CREAT | O_EXCL open
+		 * flags.
+		 */
+		mktemp(tmp_name);
+		if (tmp_name[0] == '\0') {
+			PERROR("mktemp");
+			goto error_shm_open;
+		}
+		shmfd = shm_open(tmp_name,
 				 O_CREAT | O_EXCL | O_RDWR, 0700);
-	} while (shmfd < 0 && errno == EEXIST);
+	} while (shmfd < 0 && (errno == EEXIST || errno == EACCES));
 	if (shmfd < 0) {
 		PERROR("shm_open");
 		goto error_shm_open;
 	}
-	ret = shm_unlink("ust-shm-tmp");
-	if (ret) {
+	ret = shm_unlink(tmp_name);
+	if (ret < 0 && errno != ENOENT) {
 		PERROR("shm_unlink");
-		goto error_unlink;
+		goto error_shm_release;
+	}
+	sigblocked = 0;
+	ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL);
+	if (ret == -1) {
+		PERROR("pthread_sigmask");
+		goto error_sigmask_release;
 	}
 	ret = ftruncate(shmfd, memory_map_size);
 	if (ret) {
@@ -104,13 +137,21 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
 
 error_mmap:
 error_ftruncate:
-error_unlink:
+error_shm_release:
+error_sigmask_release:
 	ret = close(shmfd);
 	if (ret) {
 		PERROR("close");
 		assert(0);
 	}
 error_shm_open:
+	if (sigblocked) {
+		ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL);
+		if (ret == -1) {
+			PERROR("pthread_sigmask");
+		}
+	}
+error_pthread_sigmask:
 error_fcntl:
 	for (i = 0; i < 2; i++) {
 		ret = close(waitfd[i]);
@@ -120,7 +161,6 @@ error_fcntl:
 		}
 	}
 error_pipe:
-	free(obj);
 	return NULL;
 	
 }