From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 18 Jun 2005 20:51:59 +0000 (+0000)
Subject: When using C-string lookup keys in a dynahash.c hash table, use strncpy()
X-Git-Url: http://waps.l3s.uni-hannover.de/gitweb/?a=commitdiff_plain;h=e7125459a0f387cf6b4698206070d205c3b7c7cf;p=users%2Fbernd%2Fpostgres.git

When using C-string lookup keys in a dynahash.c hash table, use strncpy()
not memcpy() to copy the offered key into the hash table during HASH_ENTER.
This avoids possible core dump if the passed key is located very near the
end of memory.  Per report from Stefan Kaltenbrunner.
---

diff --git a/src/backend/utils/hash/dynahash.c b/src/backend/utils/hash/dynahash.c
index 6480993fde..9f4512eacd 100644
--- a/src/backend/utils/hash/dynahash.c
+++ b/src/backend/utils/hash/dynahash.c
@@ -144,6 +144,14 @@ hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
 	else
 		hashp->match = memcmp;
 
+	/*
+	 * Similarly, the key-copying function defaults to strncpy() or memcpy().
+	 */
+	if (hashp->hash == string_hash)
+		hashp->keycopy = (HashCopyFunc) strncpy;
+	else
+		hashp->keycopy = memcpy;
+
 	if (flags & HASH_SHARED_MEM)
 	{
 		/*
@@ -644,7 +652,7 @@ hash_search(HTAB *hashp,
 
 			/* copy key into record */
 			currBucket->hashvalue = hashvalue;
-			memcpy(ELEMENTKEY(currBucket), keyPtr, hctl->keysize);
+			hashp->keycopy(ELEMENTKEY(currBucket), keyPtr, hctl->keysize);
 
 			/* caller is expected to fill the data field on return */
 
diff --git a/src/include/utils/hsearch.h b/src/include/utils/hsearch.h
index e6b508b0d6..1d42183c8c 100644
--- a/src/include/utils/hsearch.h
+++ b/src/include/utils/hsearch.h
@@ -24,6 +24,7 @@
 typedef uint32 (*HashValueFunc) (const void *key, Size keysize);
 typedef int (*HashCompareFunc) (const void *key1, const void *key2,
 								Size keysize);
+typedef void *(*HashCopyFunc) (void *dest, const void *src, Size keysize);
 
 /*
  * Space allocation function for a hashtable --- designed to match malloc().
@@ -108,6 +109,7 @@ typedef struct HTAB
 								 * used */
 	char	   *tabname;		/* table name (for error messages) */
 	bool		isshared;		/* true if table is in shared memory */
+	HashCopyFunc keycopy;		/* key copying function */
 } HTAB;
 
 /* Parameter data structure for hash_create */