File _service:tar_scm_kernel_repo:backport-libselinu... of Package libselinux

File _service:tar_scm_kernel_repo:backport-libselinux-use-DJB2a-string-hash-function.patch of Package libselinux

From f1178a13dc8bc9e750cf59de1db8fc48867f9293 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20G=C3=B6ttsche?= <cgzones@googlemail.com>
Date: Wed, 16 Aug 2023 14:38:44 +0200
Subject: [PATCH] libselinux: use DJB2a string hash function
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The hash table implementation uses `& (SIDTAB_SIZE - 1)` to truncate
generated hashes to the number of buckets.  This operation is equal to
`% SIDTAB_SIZE` if and only if the size is a power of two (which seems
to be always the case).  One property of the binary and with a power of
two (and probably a small one <=2048) is all higher bits are discarded.
Thus a hash function is needed with a good avalanche effect, which the
current one is not.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Acked-by: James Carter <jwcart2@gmail.com>
---
 libselinux/src/avc_sidtab.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/src/avc_sidtab.c b/src/avc_sidtab.c
index f179d855..e396a938 100644
--- a/src/avc_sidtab.c
+++ b/src/avc_sidtab.c
@@ -15,16 +15,13 @@
 
 static inline unsigned sidtab_hash(const char * key)
 {
-	const char *p;
-	unsigned int size;
-	unsigned int val;
-
-	val = 0;
-	size = strlen(key);
-	for (p = key; (unsigned int)(p - key) < size; p++)
-		val =
-		    (val << 4 | (val >> (8 * sizeof(unsigned int) - 4))) ^ (*p);
-	return val & (SIDTAB_SIZE - 1);
+	unsigned int hash = 5381;
+	unsigned char c;
+
+	while ((c = *(unsigned const char *)key++))
+		hash = ((hash << 5) + hash) ^ c;
+
+	return hash & (SIDTAB_SIZE - 1);
 }
 
 int sidtab_init(struct sidtab *s)
-- 
2.27.0