Don't use memcpy when source and dest. buffers may overlap

meyering · Junio C Hamano · commit 554a2636f7c5 · 2006-12-11T14:04:43.000-08:00
git-index-pack can call memcpy with overlapping source and destination
buffers.  The patch below makes it use memmove instead.

If you want to demonstrate a failure, add the following two lines

+               if (input_offset &lt; input_len)
+                 abort ();

before the existing memcpy call (shown in the patch below),
and then run this:

  (cd t; sh ./t5500-fetch-pack.sh)

Signed-off-by: Jim Meyering &lt;jim@meyering.net&gt;
Signed-off-by: Junio C Hamano &lt;junkio@cox.net&gt;
diff --git a/index-pack.c b/index-pack.c
@@ -96,7 +96,7 @@ static void flush(void)
 		if (output_fd >= 0)
 			write_or_die(output_fd, input_buffer, input_offset);
 		SHA1_Update(&input_ctx, input_buffer, input_offset);
-		memcpy(input_buffer, input_buffer + input_offset, input_len);
+		memmove(input_buffer, input_buffer + input_offset, input_len);
 		input_offset = 0;
 	}
 }

Original file line number	Diff line number	Diff line change
`@@ -96,7 +96,7 @@ static void flush(void)`
`96`	`96`	`if (output_fd >= 0)`
`97`	`97`	`write_or_die(output_fd, input_buffer, input_offset);`
`98`	`98`	`SHA1_Update(&input_ctx, input_buffer, input_offset);`
`99`		`- memcpy(input_buffer, input_buffer + input_offset, input_len);`
	`99`	`+ memmove(input_buffer, input_buffer + input_offset, input_len);`
`100`	`100`	`input_offset = 0;`
`101`	`101`	`}`
`102`	`102`	`}`