linux-kernel - [PATCH v4 5/8] ARM: kexec: Make .text R/W in machine

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1407949593-16121-6-git-send-email-keescook@chromium.org>
Date:	Wed, 13 Aug 2014 10:06:30 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	Kees Cook <keescook@...omium.org>,
	Nikolay Borisov <Nikolay.Borisov@....com>,
	Rob Herring <robh@...nel.org>,
	Laura Abbott <lauraa@...eaurora.org>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Mark Salter <msalter@...hat.com>, Rabin Vincent <rabin@....in>,
	Liu hua <sdu.liu@...wei.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Doug Anderson <dianders@...gle.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org
Subject: [PATCH v4 5/8] ARM: kexec: Make .text R/W in machine_kexec

From: Nikolay Borisov <Nikolay.Borisov@....com>

With the introduction of Kees Cook's patch to make the kernel .text
read-only the existing method by which kexec works got broken since it
directly pokes some values in the template code, which resides in the
.text section.

The current patch changes the way those values are inserted so that poking
.text section occurs only in machine_kexec (e.g when we are about to nuke
the old kernel and are beyond the point of return). This allows to use
set_kernel_text_rw() to directly patch the values in the .text section.

I had already sent a patch which achieved this but it was significantly
more complicated, so this is a cleaner/straight-forward approach.

Signed-off-by: Nikolay Borisov <Nikolay.Borisov@....com>
Acked-by: Will Deacon <will.deacon@....com>
[kees: collapsed kexec_boot_atags (will.daecon)]
[kees: for bisectability, moved set_kernel_text_rw() to RODATA patch]
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/arm/kernel/machine_kexec.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 8cf0996aa1a8..8f75250cbe30 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -29,6 +29,7 @@ extern unsigned long kexec_boot_atags;
 
 static atomic_t waiting_for_crash_ipi;
 
+static unsigned long dt_mem;
 /*
  * Provide a dummy crash_notes definition while crash dump arrives to arm.
  * This prevents breakage of crash_notes attribute in kernel/ksysfs.c.
@@ -64,7 +65,7 @@ int machine_kexec_prepare(struct kimage *image)
 			return err;
 
 		if (be32_to_cpu(header) == OF_DT_HEADER)
-			kexec_boot_atags = current_segment->mem;
+			dt_mem = current_segment->mem;
 	}
 	return 0;
 }
@@ -166,9 +167,8 @@ void machine_kexec(struct kimage *image)
 	kexec_start_address = image->start;
 	kexec_indirection_page = page_list;
 	kexec_mach_type = machine_arch_type;
-	if (!kexec_boot_atags)
-		kexec_boot_atags = image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET;
-
+	kexec_boot_atags = dt_mem ?: image->start - KEXEC_ARM_ZIMAGE_OFFSET
+				     + KEXEC_ARM_ATAGS_OFFSET;
 
 	/* copy our kernel relocation code to the control code page */
 	reboot_entry = fncpy(reboot_code_buffer,
-- 
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/