lkml.org 
[lkml]   [2020]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
SubjectRe: [PATCH v2 1/1] selinux: fix another double free
On Thu, Jun 11, 2020 at 4:48 PM <trix@redhat.com> wrote:
> From: Tom Rix <trix@redhat.com>
>
> 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
> earlier nodes.
>
> Because cond_read_node no longer does any error handling, the goto's
> the error case are redundant. Instead just return the error code.
>
> Fixes a problem was introduced by commit
>
> selinux: convert cond_list to array
>
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
> security/selinux/ss/conditional.c | 11 +++--------
> 1 file changed, 3 insertions(+), 8 deletions(-)

Hi Tom,

Thanks for the patch! A few more notes, in no particular order:

* There is no need to send a cover letter for just a single patch.
Typically cover letters are reserved for large patchsets that require
some additional explanation and/or instructions beyond the individual
commit descriptions.

* Thank you for including a changelog with your patch updates, but it
would be helpful if you included them in the patch by using a "---"
delimiter in the commit description after your signoff but before the
diffstat. Here is a recent example:
-> https://lore.kernel.org/selinux/20200611135303.19538-3-cgzones@googlemail.com

* When referencing a patch which you are "fixing", the proper syntax
is 'Fixes: <12char_commitID> ("<subject_line")'. Look at commit
46619b44e431 in Linus' tree to see an example.

If you have any questions, let us know.

> diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
> index da94a1b4bfda..d0d6668709f0 100644
> --- a/security/selinux/ss/conditional.c
> +++ b/security/selinux/ss/conditional.c
> @@ -392,26 +392,21 @@ static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
>
> rc = next_entry(buf, fp, sizeof(u32) * 2);
> if (rc)
> - goto err;
> + return rc;
>
> expr->expr_type = le32_to_cpu(buf[0]);
> expr->bool = le32_to_cpu(buf[1]);
>
> if (!expr_node_isvalid(p, expr)) {
> rc = -EINVAL;
> - goto err;
> + return rc;
> }
> }
>
> rc = cond_read_av_list(p, fp, &node->true_list, NULL);
> if (rc)
> - goto err;
> + return rc;
> rc = cond_read_av_list(p, fp, &node->false_list, &node->true_list);
> - if (rc)
> - goto err;
> - return 0;
> -err:
> - cond_node_destroy(node);
> return rc;
> }
>
> --
> 2.18.1

--
paul moore
www.paul-moore.com

\
 
 \ /
  Last update: 2020-06-12 00:31    [W:0.058 / U:0.892 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site