linux-kernel - Re: [PATCH v2] audit: fix suffixed '/' filename matching in __audit_inode

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Message-ID: <d3391fbff2c69be230d368c68d215be4@paul-moore.com>
Date: Thu, 05 Dec 2024 19:22:37 -0500
From: Paul Moore <paul@...l-moore.com>
To: Ricardo Robaina <rrobaina@...hat.com>, audit@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: eparis@...hat.com, rgb@...hat.com, viro@...iv.linux.org.uk, Ricardo Robaina <rrobaina@...hat.com>
Subject: Re: [PATCH v2] audit: fix suffixed '/' filename matching in  __audit_inode_child()

On Nov 22, 2024 Ricardo Robaina <rrobaina@...hat.com> wrote:
> 
> When the user specifies a directory to delete with the suffix '/',
> the audit record fails to collect the filename, resulting in the
> following logs:
> 
>  type=PATH msg=audit(10/30/2024 14:11:17.796:6304) : item=2 name=(null)
>  type=PATH msg=audit(10/30/2024 14:11:17.796:6304) : item=1 name=(null)
> 
> It happens because the value of the variables dname, and n->name->name
> in __audit_inode_child() differ only by the suffix '/'. This commit
> treats this corner case by handling pathname's trailing slashes in
> audit_compare_dname_path().
> 
> Steps to reproduce the issue:
> 
>  # auditctl -w /tmp
>  $ mkdir /tmp/foo
>  $ rm -r /tmp/foo/
>  # ausearch -i | grep PATH | tail -3
> 
> The first version of this patch was based on a GitHub patch/PR by
> user @hqh2010 [1].
> 
> Link: https://github.com/linux-audit/audit-kernel/pull/148 [1]
> 
> Suggested-by: Paul Moore <paul@...l-moore.com>
> Reviewed-by: Richard Guy Briggs <rgb@...hat.com>
> Reviewed-by: Al Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Ricardo Robaina <rrobaina@...hat.com>
> ---
> v2: handling pathname's trailing slashes in audit_compare_dname_path()
> v1: https://lore.kernel.org/audit/20241114040948.GK3387508@ZenIV/T/#t
> ---
>  kernel/auditfilter.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)

Yes, Richard did provide a reviewed-by tag on the v1 patch, but v2 has
enough changes that I don't think we can reasonably carry that forward;
of course Richard re-review this iteration and provide a new tag.  I'm
going to remove it for now.

Al never provided an explicit reviewed-by tag; simply commenting on a
patch is not the same as providing a 'Reviewed-by', the reviewer will
provide an explicit 'Reviewed-by' tag in their email.  I'm going to
remove Al's tag too.

Other than those issues, I think this looks much better than v1, I'm
going to merge this into audit/dev now, thanks!

> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index 470041c49a44..8ddccdb4a2a7 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -1319,13 +1319,20 @@ int audit_compare_dname_path(const struct qstr *dname, const char *path, int par
>  	if (pathlen < dlen)
>  		return 1;
>  
> -	parentlen = parentlen == AUDIT_NAME_FULL ? parent_len(path) : parentlen;
> -	if (pathlen - parentlen != dlen)
> -		return 1;
> +	if (parentlen == AUDIT_NAME_FULL)
> +		parentlen = parent_len(path);
>  
>  	p = path + parentlen;
>  
> -	return strncmp(p, dname->name, dlen);
> +	/* handle trailing slashes */
> +	pathlen -= parentlen;
> +	while (p[pathlen - 1] == '/')
> +		pathlen--;
> +
> +	if (pathlen != dlen)
> +		return 1;
> +
> +	return memcmp(p, dname->name, dlen);
>  }
>  
>  int audit_filter(int msgtype, unsigned int listtype)
> -- 
> 2.47.0

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