[PATCH v2] diff-delta: use safe integer arithmetic

From: Srujith A Poojary via GitGitGadget <gitgitgadget@gmail.com>
Date: Oct 23, 2026, 05:56 UTC
Message-ID: <pull.2276.v2.git.1792734993812.gitgitgadget@gmail.com>
In-Reply-To: <pull.2276.git.1792727808109.gitgitgadget@gmail.com>

From: Srujith A Poojary <poojarysrujith@gmail.com>

Replace manual multiplication and addition in create_delta_index() with safe integer helpers (st_mult, st_add, st_add3) to prevent overflows.

Signed-off-by: Srujith A Poojary <poojarysrujith@gmail.com>
---
    [Outreachy PATCH] diff-delta: use safe integer arithmetic

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2276%2Fpoojarysrujith%2Fc-refactor-target-name-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2276/poojarysrujith/c-refactor-target-name-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/2276

Range-diff vs v1:

 1:  a0aafe63a7 ! 1:  14ffd630ca [Outreachy PATCH] diff-delta: use safe integer arithmetic
     @@ Metadata
      Author: Srujith A Poojary <poojarysrujith@gmail.com>
      
       ## Commit message ##
     -    [Outreachy PATCH] diff-delta: use safe integer arithmetic
     +    diff-delta: use safe integer arithmetic
      
          Replace manual multiplication and addition in create_delta_index()
          with safe integer helpers (st_mult, st_add, st_add3) to prevent
     -    overflows while preserving NULL returns on failure.
     +    overflows.
      
          Signed-off-by: Srujith A Poojary <poojarysrujith@gmail.com>

 diff-delta.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/diff-delta.c b/diff-delta.c
index 7cbedeb507..45df070ab9 100644
--- a/diff-delta.c
+++ b/diff-delta.c
@@ -162,8 +162,8 @@ struct delta_index * create_delta_index(const void *buf, size_t bufsize)
 	hmask = hsize - 1;
 
 	/* allocate lookup index */
-	memsize = sizeof(*hash) * hsize +
-		  sizeof(*entry) * entries;
+	memsize = st_add(st_mult(sizeof(*hash), hsize),
+				st_mult(sizeof(*entry), entries));
 	mem = malloc(memsize);
 	if (!mem)
 		return NULL;
@@ -258,9 +258,9 @@ struct delta_index * create_delta_index(const void *buf, size_t bufsize)
 	 * Now create the packed index in array form
 	 * rather than linked lists.
 	 */
-	memsize = sizeof(*index)
-		+ sizeof(*packed_hash) * (hsize+1)
-		+ sizeof(*packed_entry) * entries;
+	memsize = st_add3(sizeof(*index),
+			st_mult(sizeof(*packed_hash), hsize + 1),
+			st_mult(sizeof(*packed_entry), entries));
 	mem = malloc(memsize);
 	if (!mem) {
 		free(hash);

base-commit: 47fdf2208c5b94c8cc01c106b8f7c85efb91c926

-- 
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