Blame SOURCES/0016-Issue-4521-DS-crash-in-deref-plugin-if-dereferenced-.patch

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From ffeb863e47ab35cbb2e5666847561451d0394ed9 Mon Sep 17 00:00:00 2001
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From: tbordaz <tbordaz@redhat.com>
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Date: Mon, 11 Jan 2021 17:33:06 +0100
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Subject: [PATCH] Issue 4521 - DS crash in deref plugin if dereferenced entry
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 exists but is not returned by internal search (#4525)
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Bug description:
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	For each returned entry, deref plugin dereferences some attribute values that refer to entries.
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	To do this it does an internal search (scope base) with each attribute values.
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	Deref plugin assumes that if internal search succeeds, a single entry is returned.
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	It exists cases (not identified) where internal search succeeds but returns no entry.
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	In such case (search succeeds but no entry returned) the server crash.
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	Note: wonder if DB deadlock could lead to such situation.
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Fix description:
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	Make a hardening fix that logs warning in such case
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relates: https://github.com/389ds/389-ds-base/issues/4521
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Reviewed by: Mark Reynolds (thanks)
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Platforms tested: F31
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---
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 ldap/servers/plugins/deref/deref.c | 15 +++++++++++++++
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 1 file changed, 15 insertions(+)
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diff --git a/ldap/servers/plugins/deref/deref.c b/ldap/servers/plugins/deref/deref.c
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index ec1884ba3..fc1c10f71 100644
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--- a/ldap/servers/plugins/deref/deref.c
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+++ b/ldap/servers/plugins/deref/deref.c
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@@ -592,6 +592,21 @@ deref_do_deref_attr(Slapi_PBlock *pb, BerElement *ctrlber, const char *derefdn,
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                 slapi_log_err(SLAPI_LOG_PLUGIN, DEREF_PLUGIN_SUBSYSTEM,
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                               "deref_do_deref_attr - More than one entry matching DN [%s]\n",
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                               derefdn);
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+            } else if (entries[0] == NULL) {
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+                int32_t op_id;
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+                uint64_t conn_id;
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+
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+                slapi_pblock_get(pb, SLAPI_OPERATION_ID, &op_id);
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+                slapi_pblock_get(pb, SLAPI_CONN_ID, &conn_id);
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+                /* Weird case not clearly understood:
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+                 * the entry 'derefdn' exists (else we would have NOT_SUCH_ENTRY in 'rc')
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+                 * but it is not returned by the internal search. Note that internal search
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+                 * returns tombstone or subentry.
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+                 * Just to prevent a crash, catch this error condition and log a warning
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+                 */
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+                slapi_log_err(SLAPI_LOG_WARNING, DEREF_PLUGIN_SUBSYSTEM,
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+                              "deref_do_deref_attr - conn=%" PRIu64 " op=%d - failed to retrieve the entry [%s], although the entry exists\n",
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+                              conn_id, op_id, derefdn);
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             } else {
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                 int ii;
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                 int needattrvals = 1; /* need attrvals sequence? */
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-- 
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2.26.2
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