Commit 00ec2c37 authored May 02, 2016 by Kees Cook Committed by Ingo Molnar May 03, 2016

x86/boot: Warn on future overlapping memcpy() use

If an overlapping memcpy() is ever attempted, we should at least report
it, in case it might lead to problems, so it could be changed to a
memmove() call instead.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Lasse Collin <lasse.collin@tukaani.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1462229461-3370-3-git-send-email-keescook@chromium.org

Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent dc425a6e

arch/x86/boot/compressed/string.c

+13 −3

Original line number	Diff line number	Diff line
		@@ -10,7 +10,7 @@
		#include "../string.c"

		#ifdef CONFIG_X86_32
		void memcpy(void dest, const void *src, size_t n)
		static void __memcpy(void dest, const void *src, size_t n)
		{
		int d0, d1, d2;
		asm volatile(
		@@ -24,7 +24,7 @@ void memcpy(void dest, const void *src, size_t n)
		return dest;
		}
		#else
		void memcpy(void dest, const void *src, size_t n)
		static void __memcpy(void dest, const void *src, size_t n)
		{
		long d0, d1, d2;
		asm volatile(
		@@ -55,10 +55,20 @@ void memmove(void dest, const void *src, size_t n)
		const unsigned char *s = src;

		if (d <= s \|\| d - s >= n)
		return memcpy(dest, src, n);
		return __memcpy(dest, src, n);

		while (n-- > 0)
		d[n] = s[n];

		return dest;
		}

		/* Detect and warn about potential overlaps, but handle them with memmove. */
		void memcpy(void dest, const void *src, size_t n)
		{
		if (dest > src && dest - src < n) {
		warn("Avoiding potentially unsafe overlapping memcpy()!");
		return memmove(dest, src, n);
		}
		return __memcpy(dest, src, n);
		}

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