linux-kernel - Re: [PATCH] exec: fix no kernel module found error to be more clear

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] [day] [month] [year] [list]

Message-ID: <20241115180303.GA209620@lichtman.org>
Date: Fri, 15 Nov 2024 18:03:03 +0000
From: Nir Lichtman <nir@...htman.org>
To: viro@...iv.linux.org.uk, brauner@...nel.org, jack@...e.cz,
	ebiederm@...ssion.com, kees@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] exec: fix no kernel module found error to be more clear

On Fri, Nov 15, 2024 at 04:55:41PM +0000, Nir Lichtman wrote:
> Problem: Before starting the enumeration of the supported formats the
> default return value is set to no entity which is misleading since if
> the kernel module of the binary format is not found, it would return no
> entity to user mode which is misleading since it is signaling that a
> file was not found, but in this case the more suitable error is that the
> executable has an unsupported format

Disregard this, I have come to the conclusion that it is unnecessary,
since at least one built-in binary format supported directly in the kernel 
is required for loading kernel modules, this is because the kernel executes
a user mode modprobe to load the module.

Interestingly, placing a "modprobe" in /sbin/modprobe and adding 0
supported formats in the kernel configuration, but adding module support,
results in a loop of calls to the search_binary_handler function,
since it keeps trying to load a module to load "modprobe", it does give up
though at some point and just panics as expected, but it does result in some
visible hold before hand.

Thanks and sorry for the confusion,
Nir

> 
> Solution: Refactor to return no-exec error instead
> 
> Signed-off-by: Nir Lichtman <nir@...htman.org>
> ---
>  fs/exec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/exec.c b/fs/exec.c
> index 3394de5882af..6324f9546b09 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1740,7 +1740,7 @@ static int search_binary_handler(struct linux_binprm *bprm)
>  	if (retval)
>  		return retval;
>  
> -	retval = -ENOENT;
> +	retval = -ENOEXEC;
>   retry:
>  	read_lock(&binfmt_lock);
>  	list_for_each_entry(fmt, &formats, lh) {
> -- 
> 2.39.2
>