From: Alexander Bluhm <bluhm@openbsd.org>
Subject: mbuf pulldown replace memmove with memcpy
To: tech@openbsd.org
Date: Thu, 29 Aug 2024 16:21:01 +0200

Hi,

m_pulldown() copies memory between different mbufs.  So they cannot
overlap and memcpy() should be enough.

ok?

bluhm

Index: kern/uipc_mbuf2.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/kern/uipc_mbuf2.c,v
diff -u -p -r1.46 uipc_mbuf2.c
--- kern/uipc_mbuf2.c	29 Aug 2024 10:44:40 -0000	1.46
+++ kern/uipc_mbuf2.c	29 Aug 2024 14:04:56 -0000
@@ -171,7 +171,7 @@ m_pulldown(struct mbuf *m, int off, int 
 		n->m_next->m_data -= hlen;
 		n->m_next->m_len += hlen;
 		counters_inc(mbstat, MBSTAT_PULLDOWN_COPY);
-		memmove(mtod(n->m_next, caddr_t), mtod(n, caddr_t) + off, hlen);
+		memcpy(mtod(n->m_next, caddr_t), mtod(n, caddr_t) + off, hlen);
 		n->m_len -= hlen;
 		n = n->m_next;
 		off = 0;
@@ -201,7 +201,7 @@ m_pulldown(struct mbuf *m, int off, int 
 	}
 	/* get hlen from <n, off> into <o, 0> */
 	o->m_len = hlen;
-	memmove(mtod(o, caddr_t), mtod(n, caddr_t) + off, hlen);
+	memcpy(mtod(o, caddr_t), mtod(n, caddr_t) + off, hlen);
 	n->m_len -= hlen;
 	/* get tlen from <n->m_next, 0> into <o, hlen> */
 	m_copydata(n->m_next, 0, tlen, mtod(o, caddr_t) + o->m_len);