From: Tom Rix <[email protected]>
Clang static analysis reports this double free error
security/selinux/ss/conditional.c:139:2: warning: Attempt to free released memory [unix.Malloc]
kfree(node->expr.nodes);
^~~~~~~~~~~~~~~~~~~~~~~
When cond_read_node fails, it calls cond_node_destroy which frees the
node but does not poison the entry in the node list. So when it
returns to its caller cond_read_list, cond_read_list deletes the
partial list. The latest entry in the list will be deleted twice.
So instead of freeing the node in cond_read_node, let list freeing in
code_read_list handle the freeing the problem node along with all of the the
earlier nodes.
Signed-off-by: Tom Rix <[email protected]>
---
security/selinux/ss/conditional.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index da94a1b4bfda..ffb31af22f4f 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -411,7 +411,6 @@ static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
goto err;
return 0;
err:
- cond_node_destroy(node);
return rc;
}
--
2.18.1
On Thu, Jun 11, 2020 at 11:58 AM <[email protected]> wrote:
>
> From: Tom Rix <[email protected]>
>
> Clang static analysis reports this double free error
>
> security/selinux/ss/conditional.c:139:2: warning: Attempt to free released memory [unix.Malloc]
> kfree(node->expr.nodes);
> ^~~~~~~~~~~~~~~~~~~~~~~
>
> When cond_read_node fails, it calls cond_node_destroy which frees the
> node but does not poison the entry in the node list. So when it
> returns to its caller cond_read_list, cond_read_list deletes the
> partial list. The latest entry in the list will be deleted twice.
>
> So instead of freeing the node in cond_read_node, let list freeing in
> code_read_list handle the freeing the problem node along with all of the the
> earlier nodes.
>
> Signed-off-by: Tom Rix <[email protected]>
Looks like this was introduced by
60abd3181db29ea81742106cc0ac2e27fd05b418 ("selinux: convert cond_list
to array").
Acked-by: Stephen Smalley <[email protected]>
Hi Tom,
On Thu, Jun 11, 2020 at 5:58 PM <[email protected]> wrote:
> From: Tom Rix <[email protected]>
>
> Clang static analysis reports this double free error
>
> security/selinux/ss/conditional.c:139:2: warning: Attempt to free released memory [unix.Malloc]
> kfree(node->expr.nodes);
> ^~~~~~~~~~~~~~~~~~~~~~~
>
> When cond_read_node fails, it calls cond_node_destroy which frees the
> node but does not poison the entry in the node list. So when it
> returns to its caller cond_read_list, cond_read_list deletes the
> partial list. The latest entry in the list will be deleted twice.
>
> So instead of freeing the node in cond_read_node, let list freeing in
> code_read_list handle the freeing the problem node along with all of the the
There is an extra "the" before "freeing".
> earlier nodes.
>
> Signed-off-by: Tom Rix <[email protected]>
> ---
> security/selinux/ss/conditional.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
> index da94a1b4bfda..ffb31af22f4f 100644
> --- a/security/selinux/ss/conditional.c
> +++ b/security/selinux/ss/conditional.c
> @@ -411,7 +411,6 @@ static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
> goto err;
> return 0;
> err:
> - cond_node_destroy(node);
> return rc;
Since there is now just "return rc" in the error path, can you please
replace all the gotos with plain return statements? And please also
add a Fixes: tag pointing to the commit that introduced the bug (see
Stephen's reply).
Thanks,
--
Ondrej Mosnacek
Software Engineer, Platform Security - SELinux kernel
Red Hat, Inc.