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/*
* gcc unlinkat_failure.c -o unlinkat_failure.so -shared -ldl
* LD_PRELOAD=./unlinkat_failure.so FAILURE_PATH=/etc/shadow ./test /etc/shadow
*/
#define _GNU_SOURCE
#include <dlfcn.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdarg.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
typedef int (*unlinkat_type) (int dirfd, const char *pathname, int flags);
static unlinkat_type next_unlinkat;
static const char *failure_path = NULL;
static dev_t failure_dev = -1;
static ino_t failure_ino = -1;
int unlinkat (int dirfd, const char *pathname, int flags)
{
if (NULL == next_unlinkat)
{
next_unlinkat = dlsym (RTLD_NEXT, "unlinkat");
assert (NULL != next_unlinkat);
}
if (NULL == failure_path) {
struct stat sb;
failure_path = getenv ("FAILURE_PATH");
if (NULL == failure_path) {
fputs ("No FAILURE_PATH defined\n", stderr);
}
if (lstat (failure_path, &sb) != 0) {
fputs ("Can't lstat FAILURE_PATH\n", stderr);
}
failure_dev = sb.st_dev;
failure_ino = sb.st_ino;
}
if ( (NULL != pathname)
&& (NULL != failure_path)) {
struct stat sb;
if ( (fstatat (dirfd, pathname, &sb, flags) == 0)
&& (sb.st_dev == failure_dev)
&& (sb.st_ino == failure_ino)) {
fprintf (stderr, "unlinkat FAILURE %s\n", failure_path);
errno = EBUSY;
return -1;
}
}
return next_unlinkat (dirfd, pathname, flags);
}
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