1 #include <unistd.h>
2 #include <fcntl.h>
3 #include <sys/wait.h>
4 #include "syscall.h"
5 #include "pthread_impl.h"
6
7 struct ctx {
8 int fd;
9 const char *filename;
10 int amode;
11 int p;
12 };
13
checker(void * p)14 static int checker(void *p)
15 {
16 struct ctx *c = p;
17 int ret;
18 if (__syscall(SYS_setregid, __syscall(SYS_getegid), -1)
19 || __syscall(SYS_setreuid, __syscall(SYS_geteuid), -1))
20 __syscall(SYS_exit, 1);
21 ret = __syscall(SYS_faccessat, c->fd, c->filename, c->amode, 0);
22 __syscall(SYS_write, c->p, &ret, sizeof ret);
23 return 0;
24 }
25
faccessat(int fd,const char * filename,int amode,int flag)26 int faccessat(int fd, const char *filename, int amode, int flag)
27 {
28 if (!flag || (flag==AT_EACCESS && getuid()==geteuid() && getgid()==getegid()))
29 return syscall(SYS_faccessat, fd, filename, amode, flag);
30
31 if (flag != AT_EACCESS)
32 return __syscall_ret(-EINVAL);
33
34 char stack[1024];
35 sigset_t set;
36 pid_t pid;
37 int status;
38 int ret, p[2];
39
40 if (pipe2(p, O_CLOEXEC)) return __syscall_ret(-EBUSY);
41 struct ctx c = { .fd = fd, .filename = filename, .amode = amode, .p = p[1] };
42
43 __block_all_sigs(&set);
44
45 pid = __clone(checker, stack+sizeof stack, 0, &c);
46 __syscall(SYS_close, p[1]);
47
48 if (pid<0 || __syscall(SYS_read, p[0], &ret, sizeof ret) != sizeof(ret))
49 ret = -EBUSY;
50 __syscall(SYS_close, p[0]);
51 __syscall(SYS_wait4, pid, &status, __WCLONE, 0);
52
53 __restore_sigs(&set);
54
55 return __syscall_ret(ret);
56 }
57