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#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/wait.h>
#include "syscall.h"
#include "pthread_impl.h"
struct ctx {
int fd;
const char *filename;
int amode;
};
static const int errors[] = {
0, -EACCES, -ELOOP, -ENAMETOOLONG, -ENOENT, -ENOTDIR,
-EROFS, -EBADF, -EINVAL, -ETXTBSY,
-EFAULT, -EIO, -ENOMEM,
-EBUSY
};
static int checker(void *p)
{
struct ctx *c = p;
int ret;
int i;
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);
for (i=0; i < sizeof errors/sizeof *errors - 1 && ret!=errors[i]; i++);
return i;
}
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 ret = -EBUSY;
struct ctx c = { .fd = fd, .filename = filename, .amode = amode };
__block_all_sigs(&set);
pid = __clone(checker, stack+sizeof stack, 0, &c);
if (pid > 0) {
int status;
do {
__syscall(SYS_wait4, pid, &status, __WCLONE, 0);
} while (!WIFEXITED(status) && !WIFSIGNALED(status));
if (WIFEXITED(status))
ret = errors[WEXITSTATUS(status)];
}
__restore_sigs(&set);
return __syscall_ret(ret);
}
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