From 26e33b1984cce3549df170f58f8221201ad54cfd Mon Sep 17 00:00:00 2001
From: Alexey Tikhonov <atikhono@redhat.com>
Date: Tue, 7 Jan 2020 16:29:05 +0100
Subject: [PATCH] util/sss_ptr_hash: fixed double free in
 sss_ptr_hash_delete_cb()
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Calling data->callback(value->ptr) in sss_ptr_hash_delete_cb() could lead
to freeing of value->ptr and thus to destruction of value->spy that is
attached to value->ptr.
In turn sss_ptr_hash_spy_destructor() calls sss_ptr_hash_delete() ->
hash_delete() -> sss_ptr_hash_delete_cb() again and in this recursive
execution hash entry was actually deleted and value was freed.
When stack was unwound back to "first" sss_ptr_hash_delete_cb() it tried
to free value again => double free.

To prevent this bug value and hence spy are now freed before execution of
data->callback(value->ptr).

Resolves: https://pagure.io/SSSD/sssd/issue/4135

Reviewed-by: Pavel Březina <pbrezina@redhat.com>
---
 src/util/sss_ptr_hash.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/util/sss_ptr_hash.c b/src/util/sss_ptr_hash.c
index c7403ffa6..8f9762cb9 100644
--- a/src/util/sss_ptr_hash.c
+++ b/src/util/sss_ptr_hash.c
@@ -154,13 +154,13 @@ sss_ptr_hash_delete_cb(hash_entry_t *item,
     callback_entry.value.type = HASH_VALUE_PTR;
     callback_entry.value.ptr = value->ptr;
 
+    /* Free value, this also will disable spy */
+    talloc_free(value);
+
     /* Switch to the input value and call custom callback. */
     if (data->callback != NULL) {
         data->callback(&callback_entry, deltype, data->pvt);
     }
-
-    /* Free value. */
-    talloc_free(value);
 }
 
 hash_table_t *sss_ptr_hash_create(TALLOC_CTX *mem_ctx,
-- 
2.20.1