This is a note to let you know that I've just added the patch titled
ARM: ensure the signal page contains defined contents
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-ensure-the-signal-page-contains-defined-contents.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 9c698bff66ab4914bb3d71da7dc6112519bde23e Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Date: Fri, 29 Jan 2021 10:19:07 +0000
Subject: ARM: ensure the signal page contains defined contents
From: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
commit 9c698bff66ab4914bb3d71da7dc6112519bde23e upstream.
Ensure that the signal page contains our poison instruction to increase
the protection against ROP attacks and also contains well defined
contents.
Acked-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Nobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/kernel/signal.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -625,18 +625,20 @@ struct page *get_signal_page(void)
addr = page_address(page);
+ /* Poison the entire page */
+ memset32(addr, __opcode_to_mem_arm(0xe7fddef1),
+ PAGE_SIZE / sizeof(u32));
+
/* Give the signal return code some randomness */
offset = 0x200 + (get_random_int() & 0x7fc);
signal_return_offset = offset;
- /*
- * Copy signal return handlers into the vector page, and
- * set sigreturn to be a pointer to these.
- */
+ /* Copy signal return handlers into the page */
memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
- ptr = (unsigned long)addr + offset;
- flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
+ /* Flush out all instructions in this page */
+ ptr = (unsigned long)addr;
+ flush_icache_range(ptr, ptr + PAGE_SIZE);
return page;
}
Patches currently in stable-queue which might be from rmk+kernel@xxxxxxxxxxxxxxx are
queue-4.4/lib-string.c-add-multibyte-memset-functions.patch
queue-4.4/arm-ensure-the-signal-page-contains-defined-contents.patch
