From: Ben Gras <ben@minix3.org>
Date: Wed, 20 Feb 2013 19:29:09 +0000 (+0100)
Subject: ARM: kernel: fix sanity check for copying
X-Git-Tag: v3.3.0~1139
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/zlib_tech.html?a=commitdiff_plain;h=2aa82a9c7ba80ca1eb07b0db118e2316581baa92;p=minix.git

ARM: kernel: fix sanity check for copying

	. phys_copy() (taken from memcpy) can legitimately
	  cause pagefaults below the source/dest address due
	  to word-alignment

Change-Id: Ibee8f069781d16caea671246c021fb17a2a892b1
---

diff --git a/kernel/arch/earm/memory.c b/kernel/arch/earm/memory.c
index f31a1bf4e..e3ebedd2d 100644
--- a/kernel/arch/earm/memory.c
+++ b/kernel/arch/earm/memory.c
@@ -196,12 +196,19 @@ static int lin_lin_copy(struct proc *srcproc, vir_bytes srclinaddr,
 		PHYS_COPY_CATCH(srcptr, dstptr, chunk, addr);
 
 		if(addr) {
-			/* If addr is nonzero, a page fault was caught. */
-
-			if(addr >= srcptr && addr < (srcptr + chunk)) {
+			/* If addr is nonzero, a page fault was caught.
+			 *
+			 * phys_copy does all memory accesses word-aligned (rounded
+			 * down), so pagefaults can occur at a lower address than
+			 * the specified offsets. compute the lower bounds for sanity
+			 * check use.
+			 */
+			vir_bytes src_aligned = srcptr & ~0x3, dst_aligned = dstptr & ~0x3;
+
+			if(addr >= src_aligned && addr < (srcptr + chunk)) {
 				return EFAULT_SRC;
 			}
-			if(addr >= dstptr && addr < (dstptr + chunk)) {
+			if(addr >= dst_aligned && addr < (dstptr + chunk)) {
 				return EFAULT_DST;
 			}