linux-kernel - Re: [PATCH v7 2/7] selftests: x86: test_mremap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f300404f-91a9-40ae-8fcc-2e855b43ac76@lucifer.local>
Date: Tue, 25 Feb 2025 06:15:40 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: jeffxu@...omium.org
Cc: akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com,
        torvalds@...ux-foundation.org, vbabka@...e.cz, Liam.Howlett@...cle.com,
        adhemerval.zanella@...aro.org, oleg@...hat.com, avagin@...il.com,
        benjamin@...solutions.net, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org, linux-mm@...ck.org,
        jorgelo@...omium.org, sroettger@...gle.com, hch@....de,
        ojeda@...nel.org, thomas.weissschuh@...utronix.de, adobriyan@...il.com,
        johannes@...solutions.net, pedro.falcato@...il.com, hca@...ux.ibm.com,
        willy@...radead.org, anna-maria@...utronix.de, mark.rutland@....com,
        linus.walleij@...aro.org, Jason@...c4.com, deller@....de,
        rdunlap@...radead.org, davem@...emloft.net, peterx@...hat.com,
        f.fainelli@...il.com, gerg@...nel.org, dave.hansen@...ux.intel.com,
        mingo@...nel.org, ardb@...nel.org, mhocko@...e.com,
        42.hyeyoo@...il.com, peterz@...radead.org, ardb@...gle.com,
        enh@...gle.com, rientjes@...gle.com, groeck@...omium.org,
        mpe@...erman.id.au, aleksandr.mikhalitsyn@...onical.com,
        mike.rapoport@...il.com, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v7 2/7] selftests: x86: test_mremap_vdso: skip if vdso is
 msealed

On Mon, Feb 24, 2025 at 10:52:41PM +0000, jeffxu@...omium.org wrote:
> From: Jeff Xu <jeffxu@...omium.org>
>
> Add code to detect if the vdso is memory sealed, skip the test
> if it is.

I feel this is a little succinct of a commit message, but I guess it gets to the
heart of what you're doing here.

Fundamentally I mean it makes sense, but I'm concerned that x86 has a test
-expliictly checking- whether mremap() of VDSO is possible - are there cases
where x86 might want to do this internal to the kernel?

I guess not since this is essentially a userland self test and probably
asserting you can do this in the way rr, etc. do.

>
> Signed-off-by: Jeff Xu <jeffxu@...omium.org>
> Reviewed-by: Kees Cook <kees@...nel.org>

Anyway, this aside, this looks fine, aside from nit below, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  .../testing/selftests/x86/test_mremap_vdso.c  | 43 +++++++++++++++++++
>  1 file changed, 43 insertions(+)
>
> diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
> index d53959e03593..94bee6e0c813 100644
> --- a/tools/testing/selftests/x86/test_mremap_vdso.c
> +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
> @@ -14,6 +14,7 @@
>  #include <errno.h>
>  #include <unistd.h>
>  #include <string.h>
> +#include <stdbool.h>
>
>  #include <sys/mman.h>
>  #include <sys/auxv.h>
> @@ -55,13 +56,55 @@ static int try_to_remap(void *vdso_addr, unsigned long size)
>
>  }
>
> +#define VDSO_NAME "[vdso]"
> +#define VMFLAGS "VmFlags:"
> +#define MSEAL_FLAGS "sl"
> +#define MAX_LINE_LEN 512
> +
> +bool vdso_sealed(FILE *maps)

Should be static?

> +{
> +	char line[MAX_LINE_LEN];
> +	bool has_vdso = false;
> +
> +	while (fgets(line, sizeof(line), maps)) {
> +		if (strstr(line, VDSO_NAME))
> +			has_vdso = true;
> +
> +		if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) {
> +			if (strstr(line, MSEAL_FLAGS))
> +				return true;
> +
> +			return false;
> +		}
> +	}
> +
> +	return false;
> +}
> +
>  int main(int argc, char **argv, char **envp)
>  {
>  	pid_t child;
> +	FILE *maps;
>
>  	ksft_print_header();
>  	ksft_set_plan(1);
>
> +	maps = fopen("/proc/self/smaps", "r");
> +	if (!maps) {
> +		ksft_test_result_skip(
> +			"Could not open /proc/self/smaps, errno=%d\n",
> +			 errno);
> +
> +		return 0;
> +	}
> +
> +	if (vdso_sealed(maps)) {
> +		ksft_test_result_skip("vdso is sealed\n");
> +		return 0;
> +	}
> +
> +	fclose(maps);
> +
>  	child = fork();
>  	if (child == -1)
>  		ksft_exit_fail_msg("failed to fork (%d): %m\n", errno);
> --
> 2.48.1.658.g4767266eb4-goog
>