On 9/24/2010 1:45 PM, Eric Paris wrote:
> With the (long ago) interface change to have the secid_to_secctx functions
> do the string allocation instead of having the caller do the allocation we
> lost the ability to query the security server for the length of the
> upcoming string. The SECMARK code would like to allocate a netlink skb
> with enough length to hold the string but it is just too unclean to do the
> string allocation twice or to do the allocation the first time and hold
> onto the string and slen. This patch adds the ability to call
> security_secid_to_secctx() with a NULL data pointer and it will just set
> the slen pointer.
>
> Signed-off-by: Eric Paris <eparis@xxxxxxxxxx>
Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
For the Smack bit at least.
> ---
>
> security/selinux/ss/services.c | 11 +++++++++--
> security/smack/smack_lsm.c | 3 ++-
> 2 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
> index 73508af..1d4955a 100644
> --- a/security/selinux/ss/services.c
> +++ b/security/selinux/ss/services.c
> @@ -998,7 +998,8 @@ static int context_struct_to_string(struct context *context, char **scontext, u3
> {
> char *scontextp;
>
> - *scontext = NULL;
> + if (scontext)
> + *scontext = NULL;
> *scontext_len = 0;
>
> if (context->len) {
> @@ -1015,6 +1016,9 @@ static int context_struct_to_string(struct context *context, char **scontext, u3
> *scontext_len += strlen(sym_name(&policydb, SYM_TYPES, context->type - 1)) + 1;
> *scontext_len += mls_compute_context_len(context);
>
> + if (!scontext)
> + return 0;
> +
> /* Allocate space for the context; caller must free this space. */
> scontextp = kmalloc(*scontext_len, GFP_ATOMIC);
> if (!scontextp)
> @@ -1054,7 +1058,8 @@ static int security_sid_to_context_core(u32 sid, char **scontext,
> struct context *context;
> int rc = 0;
>
> - *scontext = NULL;
> + if (scontext)
> + *scontext = NULL;
> *scontext_len = 0;
>
> if (!ss_initialized) {
> @@ -1062,6 +1067,8 @@ static int security_sid_to_context_core(u32 sid, char **scontext,
> char *scontextp;
>
> *scontext_len = strlen(initial_sid_to_string[sid]) + 1;
> + if (!scontext)
> + goto out;
> scontextp = kmalloc(*scontext_len, GFP_ATOMIC);
> if (!scontextp) {
> rc = -ENOMEM;
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index c448d57..b95d7b1 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -3005,7 +3005,8 @@ static int smack_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> {
> char *sp = smack_from_secid(secid);
>
> - *secdata = sp;
> + if (secdata)
> + *secdata = sp;
> *seclen = strlen(sp);
> return 0;
> }
>
>
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