Re: [PATCH] Implement glibc *_chk interfaces for ABI compatibility.

[Szabolcs Nagy <nsz@port70.net>]

* Josiah Worcester <josiahw@gmail.com> [2015-06-16 21:48:11 -0500]:
> --- /dev/null
> +++ b/src/compat/gnu_chk.c
> @@ -0,0 +1,18 @@
> +#define _GNU_SOURCE
> +#include <string.h>
> +#include <poll.h>
> +#include <stddef.h>
> +#include "atomic.h"
> +#include "atomic.h"
> +
> +int __ppoll_chk(struct pollfd *fds, nfds_t n, const struct timespec *to, const sigset_t *mask, size_t fdslen)
> +{
> +	if (fdslen / sizeof(*fds) < n) a_crash();
> +	return ppoll(fds, n, to, mask);
> +}
> +
> +void *__mempcpy_chk(void *dest, const void *src, size_t n, size_t destlen)
> +{
> +	if (destlen < n) a_crash();
> +	return mempcpy(dest, src, n);
> +}

one atomic is enough

> +char *__gets_chk(char *buf, size_t size)
> +{
> +	char *ret = buf;
> +	int c;
> +	FLOCK(stdin);
> +	if (!size) return NULL;
> +	for(;size;buf++,size--) {
> +		c = getc(stdin);
> +		if ((c == EOF && feof(stdin)) || c == '\n') {
> +			*buf = 0;
> +			FUNLOCK(stdin);
> +			return ret;
> +		}
> +		if (c == EOF) {
> +			FUNLOCK(stdin);
> +			return NULL;
> +		}
> +		*buf = c;
> +	}
> +	a_crash();
> +}

this looks wrong if !size

i think that line should be just removed

> +void *__memmove_chk(void *restrict dest, const void *restrict src, size_t n, size_t destlen)
> +{
> +	if (n > destlen) a_crash();
> +	return memmove(dest, src, n);
> +}

i think restrict is wrong here

> +char *__strcat_chk(char *restrict dest, const char *restrict src, size_t destlen)
> +{
> +	size_t tot;
> +	tot = strnlen(src, destlen);
> +	if (tot > SIZE_MAX - strnlen(dest, destlen) - 1) a_crash();
> +	tot += strnlen(dest, destlen) + 1;
> +	if (tot > destlen) a_crash();
> +	return strcat(dest, src);
> +}
> +
> +char *__strncat_chk(char *restrict dest, const char *restrict src, size_t n, size_t destlen)
> +{
> +	size_t tot;
> +	tot = strnlen(dest, destlen);
> +	if (tot > SIZE_MAX - strnlen(src, n) - 1) a_crash();
> +	tot += strnlen(src, n) + 1;
> +	if (tot > destlen) a_crash();
> +	return strncat(dest, src, n);
> +}
> +

i'd store the strnlen result in a temporary var

musl is built with -ffreestanding so the compiler cannot
assume strnlen is a pure function.

> +wchar_t *__wcscat_chk(wchar_t *restrict dest, const wchar_t *src, size_t destlen)
> +{
> +	size_t tot;
> +	tot = wcsnlen(src, destlen);
> +	if (tot > SIZE_MAX - wcsnlen(dest, destlen) - 1) a_crash();
> +	tot += wcsnlen(dest, destlen) + 1;
> +	if (tot > destlen) a_crash();
> +	return wcscat(dest, src);
> +}
> +
> +wchar_t *__wcsncat_chk(wchar_t *restrict dest, const wchar_t *restrict src, size_t n, size_t destlen)
> +{
> +	size_t tot;
> +	tot = wcsnlen(dest, destlen);
> +	if (tot > SIZE_MAX - wcsnlen(src, n) - 1) a_crash();
> +	tot += wcsnlen(dest, destlen) + 1;
> +	if (tot > destlen) a_crash();
> +	return wcsncat(dest, src, n);
> +}
> +

ditto

> diff --git a/src/compat/ttyname_r_chk.c b/src/compat/ttyname_r_chk.c
> new file mode 100644
> index 0000000..50e70e5
> --- /dev/null
> +++ b/src/compat/ttyname_r_chk.c
> @@ -0,0 +1,7 @@
> +#include <unistd.h>
> +
> +int __ttyname_r_chk(int fd, char *name, size_t size, size_t namelen)
> +{
> +	if (size > namelen) a_crash();
> +	return ttyname_r(fd, name, size);
> +}

missing atomic.h for a_crash

shouldnt this be in posix_chk.c?

> +size_t __wcrtomb_chk(char *restrict s, wchar_t wc, mbstate_t *restrict st, size_t slen)
> +{
> +	if (slen < MB_CUR_MAX) a_crash();
> +	return wcrtomb(s, wc, st);
> +}

i think this can cause a false positive crash
but glibc seems to do the same..

(eg some api passes wchar_t* and the exact mb encoded length of
a string so the output s can be safely shorter than max mb length)