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    Subject[PATCH 5.7 427/477] selinux: fix a double free in cond_read_node()/cond_read_list()
    Date
    From: Tom Rix <trix@redhat.com>

    commit aa449a7965a6172a89d48844c313708962216f1f upstream.

    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: 60abd3181db2 ("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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    security/selinux/ss/conditional.c | 18 +++++-------------
    1 file changed, 5 insertions(+), 13 deletions(-)

    --- a/security/selinux/ss/conditional.c
    +++ b/security/selinux/ss/conditional.c
    @@ -392,27 +392,19 @@ static int cond_read_node(struct policyd

    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)

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