linux-kernel - Re: [PATCH] generic/633: adapt execveat() invocations

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Date:   Mon, 31 Jan 2022 12:46:27 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Christian Brauner <brauner@...nel.org>
Cc:     Eryu Guan <guan@...u.me>, fstests@...r.kernel.org,
        Ariadne Conill <ariadne@...eferenced.org>,
        Rich Felker <dalias@...c.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Eryu Guan <guaneryu@...il.com>
Subject: Re: [PATCH] generic/633: adapt execveat() invocations

On Mon, Jan 31, 2022 at 06:10:23PM +0100, Christian Brauner wrote:
> There's a push by Ariadne to enforce that argv[0] cannot be NULL. So far
> we've allowed this. Fix the execveat() invocations to set argv[0] to the
> name of the file we're about to execute.

To be clear, these tests are also trying to launch set-id binaries with
argc == 0, so narrowing the kernel check to only set-id binaries
wouldn't help here, yes?

-Kees

> 
> Cc: Ariadne Conill <ariadne@...eferenced.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Rich Felker <dalias@...c.org>
> Cc: Eryu Guan <guaneryu@...il.com>
> Cc: Michael Kerrisk <mtk.manpages@...il.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: fstests@...r.kernel.org
> Cc: linux-fsdevel@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Link: https://lore.kernel.org/lkml/20220127000724.15106-1-ariadne@dereferenced.org
> Signed-off-by: Christian Brauner <brauner@...nel.org>
> ---
>  src/idmapped-mounts/idmapped-mounts.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/src/idmapped-mounts/idmapped-mounts.c b/src/idmapped-mounts/idmapped-mounts.c
> index 4cf6c3bb..76b559ae 100644
> --- a/src/idmapped-mounts/idmapped-mounts.c
> +++ b/src/idmapped-mounts/idmapped-mounts.c
> @@ -3598,7 +3598,7 @@ static int setid_binaries(void)
>  			NULL,
>  		};
>  		static char *argv[] = {
> -			NULL,
> +			"",
>  		};
>  
>  		if (!expected_uid_gid(t_dir1_fd, FILE1, 0, 5000, 5000))
> @@ -3726,7 +3726,7 @@ static int setid_binaries_idmapped_mounts(void)
>  			NULL,
>  		};
>  		static char *argv[] = {
> -			NULL,
> +			"",
>  		};
>  
>  		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 15000, 15000))
> @@ -3865,7 +3865,7 @@ static int setid_binaries_idmapped_mounts_in_userns(void)
>  			NULL,
>  		};
>  		static char *argv[] = {
> -			NULL,
> +			"",
>  		};
>  
>  		if (!switch_userns(attr.userns_fd, 0, 0, false))
> @@ -3924,7 +3924,7 @@ static int setid_binaries_idmapped_mounts_in_userns(void)
>  			NULL,
>  		};
>  		static char *argv[] = {
> -			NULL,
> +			"",
>  		};
>  
>  		if (!caps_supported()) {
> @@ -3992,7 +3992,7 @@ static int setid_binaries_idmapped_mounts_in_userns(void)
>  			NULL,
>  		};
>  		static char *argv[] = {
> -			NULL,
> +			"",
>  		};
>  
>  		if (!switch_userns(attr.userns_fd, 0, 0, false))
> @@ -4150,7 +4150,7 @@ static int setid_binaries_idmapped_mounts_in_userns_separate_userns(void)
>  			NULL,
>  		};
>  		static char *argv[] = {
> -			NULL,
> +			"",
>  		};
>  
>  		userns_fd = get_userns_fd(0, 10000, 10000);
> @@ -4214,7 +4214,7 @@ static int setid_binaries_idmapped_mounts_in_userns_separate_userns(void)
>  			NULL,
>  		};
>  		static char *argv[] = {
> -			NULL,
> +			"",
>  		};
>  
>  		userns_fd = get_userns_fd(0, 10000, 10000);
> @@ -4286,7 +4286,7 @@ static int setid_binaries_idmapped_mounts_in_userns_separate_userns(void)
>  			NULL,
>  		};
>  		static char *argv[] = {
> -			NULL,
> +			"",
>  		};
>  
>  		userns_fd = get_userns_fd(0, 10000, 10000);
> 
> base-commit: d8dee1222ecdfa1cff1386a61248e587eb3b275d
> -- 
> 2.32.0
> 

-- 
Kees Cook