Fix BZ#20544 (assert function passed to atexit/on_exit/__cxa_atexit != NULL)
Commit Message
Greetings,
As discussed in bz#20544 and in
http://sourceware.org/glibc/wiki/Style_and_Conventions#Invalid_pointers,
we should assert that the function passed to atexit, on_exit, etc. is
not NULL.
2018-08-27 Paul Pluzhnikov <ppluzhnikov@google.com>
[BZ #20544]
* stdlib/cxa_atexit.c (__internal_atexit): assert func != NULL.
* stdlib/on_exit.c (__on_exit): Likewise.
Comments
On 08/27/2018 02:12 PM, Paul Pluzhnikov wrote:
> Greetings,
>
> As discussed in bz#20544 and in
> http://sourceware.org/glibc/wiki/Style_and_Conventions#Invalid_pointers,
> we should assert that the function passed to atexit, on_exit, etc. is
> not NULL.
This needs a test case that forks a child, runs the test, and catches a
SIGABRT showing the failure resulting from the invalid API call.
The test should cover all of the APIs we can tests by passing NULL.
It is OK to call __cxa_atexit directly even though that might be invalid
in a real program.
> 2018-08-27 Paul Pluzhnikov <ppluzhnikov@google.com>
>
> [BZ #20544]
> * stdlib/cxa_atexit.c (__internal_atexit): assert func != NULL.
> * stdlib/on_exit.c (__on_exit): Likewise.
>
>
> -- Paul Pluzhnikov
>
>
> glibc-bz20544-20180825.txt
>
>
> diff --git a/stdlib/cxa_atexit.c b/stdlib/cxa_atexit.c
> index 6d65f7e615..978f873990 100644
> --- a/stdlib/cxa_atexit.c
> +++ b/stdlib/cxa_atexit.c
> @@ -36,6 +36,9 @@ __internal_atexit (void (*func) (void *), void *arg, void *d,
> {
> struct exit_function *new;
>
> + /* BZ#20544 */
This should comment on why the assert is here.
/* As a QoI issue we detect NULL early with an assertion instead
of a SIGSEGV at program exit when the handler is run. */
> + assert (func != NULL);
> +
> __libc_lock_lock (__exit_funcs_lock);
> new = __new_exitfn (listp);
>
> diff --git a/stdlib/on_exit.c b/stdlib/on_exit.c
> index 5241e0d86f..0ead1eafd4 100644
> --- a/stdlib/on_exit.c
> +++ b/stdlib/on_exit.c
> @@ -15,6 +15,7 @@
> License along with the GNU C Library; if not, see
> <http://www.gnu.org/licenses/>. */
>
> +#include <assert.h>
OK.
> #include <stdlib.h>
> #include "exit.h"
> #include <sysdep.h>
> @@ -25,6 +26,9 @@ __on_exit (void (*func) (int status, void *arg), void *arg)
> {
> struct exit_function *new;
>
> + /* BZ#20544 */
Likewise.
> + assert (func != NULL);
> +
> __libc_lock_lock (__exit_funcs_lock);
> new = __new_exitfn (&__exit_funcs);
>
@@ -36,6 +36,9 @@ __internal_atexit (void (*func) (void *), void *arg, void *d,
{
struct exit_function *new;
+ /* BZ#20544 */
+ assert (func != NULL);
+
__libc_lock_lock (__exit_funcs_lock);
new = __new_exitfn (listp);
@@ -15,6 +15,7 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#include <assert.h>
#include <stdlib.h>
#include "exit.h"
#include <sysdep.h>
@@ -25,6 +26,9 @@ __on_exit (void (*func) (int status, void *arg), void *arg)
{
struct exit_function *new;
+ /* BZ#20544 */
+ assert (func != NULL);
+
__libc_lock_lock (__exit_funcs_lock);
new = __new_exitfn (&__exit_funcs);