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Re: [PATCH] elf: Assert that objects are relocated before their constructors run
- From: Carlos O'Donell <carlos at redhat dot com>
- To: Florian Weimer <fweimer at redhat dot com>, libc-alpha at sourceware dot org
- Date: Wed, 11 Sep 2019 08:35:09 -0400
- Subject: Re: [PATCH] elf: Assert that objects are relocated before their constructors run
- References: <87pnk7w3y3.fsf@oldenburg2.str.redhat.com>
On 9/11/19 5:57 AM, Florian Weimer wrote:
> If we try to run constructors before relocation, this is always
> a dynamic linker bug. An assert is easier to notice than a call
> via an invalid function pointer (which may not even produce a valid
> call stack).
>
> 2019-09-11 Florian Weimer <fweimer@redhat.com>
>
> * elf/dl-init.c (call_init): Assert that the object has been
> relocated.
OK for master.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> diff --git a/elf/dl-init.c b/elf/dl-init.c
> index 3721bca81e..a998992544 100644
> --- a/elf/dl-init.c
> +++ b/elf/dl-init.c
> @@ -16,6 +16,7 @@
> License along with the GNU C Library; if not, see
> <https://www.gnu.org/licenses/>. */
>
> +#include <assert.h>
> #include <stddef.h>
> #include <ldsodefs.h>
>
> @@ -27,6 +28,11 @@ typedef void (*init_t) (int, char **, char **);
> static void
> call_init (struct link_map *l, int argc, char **argv, char **env)
> {
> + /* If the object has not been relocated, this is a bug. The
> + function pointers are invalid in this case. (Executables do not
> + need relocation, and neither do proxy objects.) */
> + assert (l->l_real->l_relocated || l->l_real->l_type == lt_executable);
OK. Use l_real for namespace support to work.
> +
> if (l->l_init_called)
> /* This object is all done. */
> return;
>
--
Cheers,
Carlos.