* [PATCH v3] selinux: fix another double free
@ 2020-06-15 20:45 trix
2020-06-16 8:13 ` Ondrej Mosnacek
2020-06-17 0:27 ` Paul Moore
0 siblings, 2 replies; 3+ messages in thread
From: trix @ 2020-06-15 20:45 UTC (permalink / raw)
To: paul, stephen.smalley.work, eparis, omosnace, weiyongjun1
Cc: selinux, linux-kernel, Tom Rix
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: 60abd3181db2 ("selinux: convert cond_list to array")
Signed-off-by: Tom Rix <trix@redhat.com>
---
v3: simplify returns
security/selinux/ss/conditional.c | 18 +++++-------------
1 file changed, 5 insertions(+), 13 deletions(-)
diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index da94a1b4bfda..450bc02f4cd2 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -392,27 +392,19 @@ 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;
- }
+ if (!expr_node_isvalid(p, expr))
+ return -EINVAL;
}
rc = cond_read_av_list(p, fp, &node->true_list, NULL);
if (rc)
- goto err;
- 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;
+ return rc;
+ return cond_read_av_list(p, fp, &node->false_list, &node->true_list);
}
int cond_read_list(struct policydb *p, void *fp)
--
2.18.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v3] selinux: fix another double free
2020-06-15 20:45 [PATCH v3] selinux: fix another double free trix
@ 2020-06-16 8:13 ` Ondrej Mosnacek
2020-06-17 0:27 ` Paul Moore
1 sibling, 0 replies; 3+ messages in thread
From: Ondrej Mosnacek @ 2020-06-16 8:13 UTC (permalink / raw)
To: Tom Rix
Cc: Paul Moore, Stephen Smalley, Eric Paris, Wei Yongjun,
SElinux list, Linux kernel mailing list
On Mon, Jun 15, 2020 at 10:46 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: 60abd3181db2 ("selinux: convert cond_list to array")
>
> Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
Thanks!
--
Ondrej Mosnacek
Software Engineer, Platform Security - SELinux kernel
Red Hat, Inc.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v3] selinux: fix another double free
2020-06-15 20:45 [PATCH v3] selinux: fix another double free trix
2020-06-16 8:13 ` Ondrej Mosnacek
@ 2020-06-17 0:27 ` Paul Moore
1 sibling, 0 replies; 3+ messages in thread
From: Paul Moore @ 2020-06-17 0:27 UTC (permalink / raw)
To: trix
Cc: Stephen Smalley, Eric Paris, Ondrej Mosnacek, weiyongjun1,
selinux, linux-kernel
On Mon, Jun 15, 2020 at 4:45 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: 60abd3181db2 ("selinux: convert cond_list to array")
>
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
> v3: simplify returns
>
> security/selinux/ss/conditional.c | 18 +++++-------------
> 1 file changed, 5 insertions(+), 13 deletions(-)
Merged into selinux/stable-5.8 with a better subject line. Thanks for
catching this and submitting the fix. Assuming everything goes well
I'll send this up to Linus later this week.
It might be nice to do a follow-up patch for selinux/next which folds
cond_node_destroy() into cond_list_destroy() as there is no longer a
need for that code to be in a separate function.
--
paul moore
www.paul-moore.com
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-06-16 8:13 ` Ondrej Mosnacek
2020-06-17 0:27 ` Paul Moore
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