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