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#include <unistd.h>
#include <fcntl.h>
#include <sys/wait.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_setregid, __syscall(SYS_getegid), -1)
|| __syscall(SYS_setreuid, __syscall(SYS_geteuid), -1))
__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;
pid_t pid;
int status;
int ret, p[2];
if (pipe2(p, O_CLOEXEC)) return __syscall_ret(-EBUSY);
struct ctx c = { .fd = fd, .filename = filename, .amode = amode, .p = p[1] };
__block_all_sigs(&set);
pid = __clone(checker, stack+sizeof stack, 0, &c);
__syscall(SYS_close, p[1]);
if (pid<0 || __syscall(SYS_read, p[0], &ret, sizeof ret) != sizeof(ret))
ret = -EBUSY;
__syscall(SYS_close, p[0]);
__syscall(SYS_wait4, pid, &status, __WCLONE, 0);
__restore_sigs(&set);
return __syscall_ret(ret);
}
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