clean up, bugfixes, and general improvement for shm_open/shm_unlink

1. don't make non-cloexec file descriptors
2. cancellation safety (cleanup handlers were missing, now unneeded)
3. share name validation/mapping code between open/unlink functions
4. avoid wasteful/slow syscalls

diff --git a/src/mman/shm_open.c b/src/mman/shm_open.c
index d368622d6f297be1f2a6ff4d2f778cf0d0323f82..a9be899b2b5e9718b936e792dc37fdc662ca9d7c 100644 (file)
--- a/src/mman/shm_open.c
+++ b/src/mman/shm_open.c
@@ -3,19 +3,38 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <string.h>
+#include <limits.h>
 
-int shm_open(const char *name, int flag, mode_t mode)
-{
-       int fd, dir;
+char *__strchrnul(const char *, int);
 
+static const char *mapname(const char *name, char *buf)
+{
+       char *p;
        while (*name == '/') name++;
-       if (strchr(name, '/')) {
+       if (*(p = __strchrnul(name, '/')) || p==name ||
+           (p-name <= 2 && name[0]=='.' && p[-1]=='.')) {
                errno = EINVAL;
-               return -1;
+               return 0;
        }
+       if (p-name > NAME_MAX) {
+               errno = ENAMETOOLONG;
+               return 0;
+       }
+       memcpy(buf, "/dev/shm/", 9);
+       memcpy(buf+9, name, p-name+1);
+       return buf;
+}
 
-       if ((dir = open("/dev/shm", O_DIRECTORY|O_RDONLY)) < 0) return -1;
-       fd = openat(dir, name, flag|O_NOFOLLOW|O_CLOEXEC|O_NONBLOCK, mode);
-       close(dir);
-       return fd;
+int shm_open(const char *name, int flag, mode_t mode)
+{
+       char buf[NAME_MAX+10];
+       if (!(name = mapname(name, buf))) return -1;
+       return open(name, flag|O_NOFOLLOW|O_CLOEXEC|O_NONBLOCK, mode);
+}
+
+int shm_unlink(const char *name)
+{
+       char buf[NAME_MAX+10];
+       if (!(name = mapname(name, buf))) return -1;
+       return unlink(name);
 }

diff --git a/src/mman/shm_unlink.c b/src/mman/shm_unlink.c
deleted file mode 100644 (file)
index 46e60b3..0000000
--- a/src/mman/shm_unlink.c
+++ /dev/null
@@ -1,21 +0,0 @@
-#include <sys/mman.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <unistd.h>
-#include <string.h>
-
-int shm_unlink(const char *name)
-{
-       int dir, ret;
-
-       while (*name == '/') name++;
-       if (strchr(name, '/')) {
-               errno = EINVAL;
-               return -1;
-       }
-
-       if ((dir = open("/dev/shm", O_DIRECTORY|O_RDONLY)) < 0) return -1;
-       ret = unlinkat(dir, name, 0);
-       close(dir);
-       return ret;
-}