[lxc-devel] [PATCH v2] allow lxc.cap.keep = none

[Serge Hallyn]

Quoting Dwight Engen (dwight.engen at oracle.com):
> Commit 1fb86a7c introduced a way to drop capabilities without having to
> specify them all explicitly. Unfortunately, there is no way to drop them
> all, as just specifying an empty keep list, ie:
> 
>     lxc.cap.keep =
> 
> clears the keep list, causing no capabilities to be dropped.
> 
> This change allows a special value "none" to be given, which will clear
> all keep capabilities parsed up to this point. If the last parsed value
> is none, all capabilities will be dropped.
> 
> Signed-off-by: Dwight Engen <dwight.engen at oracle.com>

Thanks.

Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>

> ---
> v2: implement as 'last wins' so none can be specified after caps, or
>     vice versa as well
> 
>  doc/lxc.container.conf.sgml.in | 5 ++++-
>  src/lxc/conf.c                 | 6 ++++++
>  src/lxc/confile.c              | 3 +++
>  3 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/lxc.container.conf.sgml.in b/doc/lxc.container.conf.sgml.in
> index 30fe4a8..2050d7c 100644
> --- a/doc/lxc.container.conf.sgml.in
> +++ b/doc/lxc.container.conf.sgml.in
> @@ -1010,7 +1010,10 @@ proc proc proc nodev,noexec,nosuid 0 0
>  	  <listitem>
>  	    <para>
>  	      Specify the capability to be kept in the container. All other
> -	      capabilities will be dropped.
> +	      capabilities will be dropped. When a special value of "none" is
> +	      encountered, lxc will clear any keep capabilities specified up
> +	      to this point. A value of "none" alone can be used to drop all
> +	      capabilities.
>  	    </para>
>  	  </listitem>
>  	</varlistentry>
> diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> index 50fff27..c8b573a 100644
> --- a/src/lxc/conf.c
> +++ b/src/lxc/conf.c
> @@ -2198,6 +2198,9 @@ static int parse_cap(const char *cap)
>  	char *ptr = NULL;
>  	int i, capid = -1;
>  
> +	if (!strcmp(cap, "none"))
> +		return -2;
> +
>  	for (i = 0; i < sizeof(caps_opt)/sizeof(caps_opt[0]); i++) {
>  
>  		if (strcmp(cap, caps_opt[i].name))
> @@ -2291,6 +2294,9 @@ static int dropcaps_except(struct lxc_list *caps)
>  
>  		capid = parse_cap(keep_entry);
>  
> +		if (capid == -2)
> +			continue;
> +
>  	        if (capid < 0) {
>  			ERROR("unknown capability %s", keep_entry);
>  			return -1;
> diff --git a/src/lxc/confile.c b/src/lxc/confile.c
> index 952b714..2455325 100644
> --- a/src/lxc/confile.c
> +++ b/src/lxc/confile.c
> @@ -1498,6 +1498,9 @@ static int config_cap_keep(const char *key, const char *value,
>                          break;
>  		}
>  
> +		if (!strcmp(token, "none"))
> +			lxc_clear_config_keepcaps(lxc_conf);
> +
>  		keeplist = malloc(sizeof(*keeplist));
>  		if (!keeplist) {
>  			SYSERROR("failed to allocate keepcap list");
> -- 
> 1.9.3
> 
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