When using C-string lookup keys in a dynahash.c hash table, use strncpy()

tglsfdc · tglsfdc · commit 6a6f2d91d4e9 · 2005-06-18T20:51:30.000Z
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
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.61 2005/05/29 04:23:06 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.62 2005/06/18 20:51:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -167,6 +167,16 @@ 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 (flags & HASH_KEYCOPY)
+		hashp->keycopy = info->keycopy;
+	else if (hashp->hash == string_hash)
+		hashp->keycopy = (HashCopyFunc) strncpy;
+	else
+		hashp->keycopy = memcpy;
+
 	if (flags & HASH_ALLOC)
 		hashp->alloc = info->alloc;
 	else
@@ -650,7 +660,7 @@ hash_search(HTAB *hashp,
 
 			/* copy key into record */
 			currBucket->hashvalue = hashvalue;
-			memcpy(ELEMENTKEY(currBucket), keyPtr, hctl->keysize);
+			hashp->keycopy(ELEMENTKEY(currBucket), keyPtr, 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
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.37 2005/06/08 23:02:05 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.38 2005/06/18 20:51:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,14 +16,25 @@
 
 
 /*
- * Hash and comparison functions must have these signatures.  Comparison
- * functions return zero for match, nonzero for no match.  (The comparison
- * function definition is designed to allow memcmp() and strncmp() to be
- * used directly as key comparison functions.)
+ * Hash functions must have this signature.
  */
 typedef uint32 (*HashValueFunc) (const void *key, Size keysize);
+
+/*
+ * Key comparison functions must have this signature.  Comparison functions
+ * return zero for match, nonzero for no match.  (The comparison function
+ * definition is designed to allow memcmp() and strncmp() to be used directly
+ * as key comparison functions.)
+ */
 typedef int (*HashCompareFunc) (const void *key1, const void *key2,
-											Size keysize);
+								Size keysize);
+
+/*
+ * Key copying functions must have this signature.  The return value is not
+ * used.  (The definition is set up to allow memcpy() and strncpy() to be
+ * used directly.)
+ */
+typedef void *(*HashCopyFunc) (void *dest, const void *src, Size keysize);
 
 /*
  * Space allocation function for a hashtable --- designed to match malloc().
@@ -103,6 +114,7 @@ typedef struct HTAB
 	HASHSEGMENT *dir;			/* directory of segment starts */
 	HashValueFunc hash;			/* hash function */
 	HashCompareFunc match;		/* key comparison function */
+	HashCopyFunc keycopy;		/* key copying function */
 	HashAllocFunc alloc;		/* memory allocator */
 	MemoryContext hcxt;			/* memory context if default allocator
 								 * used */
@@ -123,6 +135,7 @@ typedef struct HASHCTL
 	Size		entrysize;		/* total user element size in bytes */
 	HashValueFunc hash;			/* hash function */
 	HashCompareFunc match;		/* key comparison function */
+	HashCopyFunc keycopy;		/* key copying function */
 	HashAllocFunc alloc;		/* memory allocator */
 	HASHSEGMENT *dir;			/* directory of segment starts */
 	HASHHDR    *hctl;			/* location of header in shared mem */
@@ -140,6 +153,7 @@ typedef struct HASHCTL
 #define HASH_ALLOC		0x100	/* Set memory allocator */
 #define HASH_CONTEXT	0x200	/* Set explicit memory context */
 #define HASH_COMPARE	0x400	/* Set user defined comparison function */
+#define HASH_KEYCOPY	0x800	/* Set user defined key-copying function */
 
 
 /* max_dsize value to indicate expansible directory */
