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selinux: fix a double free in cond_read_node()/cond_read_list()

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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.

Cc: stable@vger.kernel.org
Fixes: 60abd3181d ("selinux: convert cond_list to array")
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
[PM: subject line tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Tom Rix 2020-06-15 13:45:48 -07:00 committed by Paul Moore
parent 65de50969a
commit aa449a7965
1 changed files with 5 additions and 13 deletions
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18
security/selinux/ss/conditional.c
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@ -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); rc = next_entry(buf, fp, sizeof(u32) * 2);
if (rc) if (rc)
goto err; return rc;
expr->expr_type = le32_to_cpu(buf[0]); expr->expr_type = le32_to_cpu(buf[0]);
expr->bool = le32_to_cpu(buf[1]); expr->bool = le32_to_cpu(buf[1]);
if (!expr_node_isvalid(p, expr)) { if (!expr_node_isvalid(p, expr))
rc = -EINVAL; return -EINVAL;
goto err;
}
} }
rc = cond_read_av_list(p, fp, &node->true_list, NULL); rc = cond_read_av_list(p, fp, &node->true_list, NULL);
if (rc) if (rc)
goto err; return rc;
rc = cond_read_av_list(p, fp, &node->false_list, &node->true_list); return 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;
} }
int cond_read_list(struct policydb *p, void *fp) int cond_read_list(struct policydb *p, void *fp)