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

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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
This commit is contained in:
Rich Felker 2012-09-30 17:53:54 -04:00
parent 2e3648b85d
commit 6e2372a86c
2 changed files with 31 additions and 33 deletions
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43
src/mman/shm_open.c
View File

@ -3,19 +3,38 @@
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <limits.h>
char *__strchrnul(const char *, int);
static const char *mapname(const char *name, char *buf)
{
char *p;
while (*name == '/') name++;
if (*(p = __strchrnul(name, '/')) || p==name ||
(p-name <= 2 && name[0]=='.' && p[-1]=='.')) {
errno = EINVAL;
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;
}
int shm_open(const char *name, int flag, mode_t mode)
{
int fd, dir;
while (*name == '/') name++;
if (strchr(name, '/')) {
errno = EINVAL;
return -1;
}
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;
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);
}

21
src/mman/shm_unlink.c
View File

@ -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;
}