On Wed, 2008-09-03 at 09:58 -0400, Eric Paris wrote:
> Fix a bug and a philosophical decision about who handles errors.
>
> security_context_to_sid_core() was leaking a context in the common case.
> This was causing problems on fedora systems which recently have started
> making extensive use of this function.
>
> In discussion it was decided that if string_to_context_struct() had an
> error it was its own responsibility to clean up any mess it created
> along the way. Remember that it is perfectly safe to call
> context_destroy() on the same context twice and so this will not
> introduce any double frees or cause issues with the other change.
Well, there are two possibilities. Either:
1) we are fine with multiple calls to context_destroy(), in which case
the original patch stands as is, or
2) we want to avoid multiple calls to context_destroy(), in which case
this patch is still wrong - the latter context_destroy() call should
only occur _before_ the out label (i.e. same place it was, only without
the conditional).
>
> Signed-off-by: Eric Paris <eparis@xxxxxxxxxx>
>
> ---
>
> Note that the last version was safe, didn't break anything, and fixed
> the problem. This one is just cleaner and makes the choice to not force
> callers to handle errors.
>
> security/selinux/ss/services.c | 6 +++---
> 1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
> index b52f923..736a066 100644
> --- a/security/selinux/ss/services.c
> +++ b/security/selinux/ss/services.c
> @@ -811,11 +811,12 @@ static int string_to_context_struct(struct policydb *pol,
> /* Check the validity of the new context. */
> if (!policydb_context_isvalid(pol, ctx)) {
> rc = -EINVAL;
> - context_destroy(ctx);
> goto out;
> }
> rc = 0;
> out:
> + if (rc)
> + context_destroy(ctx);
> return rc;
> }
>
> @@ -868,10 +869,9 @@ static int security_context_to_sid_core(const char *scontext, u32 scontext_len,
> } else if (rc)
> goto out;
> rc = sidtab_context_to_sid(&sidtab, &context, sid);
> - if (rc)
> - context_destroy(&context);
> out:
> read_unlock(&policy_rwlock);
> + context_destroy(&context);
> kfree(scontext2);
> kfree(str);
> return rc;
>
--
Stephen Smalley
National Security Agency
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