Patch "MIPS: Ensure bss section ends on a long-aligned address" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    MIPS: Ensure bss section ends on a long-aligned address

to the 4.9-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:
     mips-ensure-bss-section-ends-on-a-long-aligned-address.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Thu Oct  5 10:28:31 CEST 2017
From: Paul Burton <paul.burton@imgtec.com>
Date: Mon, 7 Nov 2016 11:52:19 +0000
Subject: MIPS: Ensure bss section ends on a long-aligned address

From: Paul Burton <paul.burton@imgtec.com>


[ Upstream commit 3f00f4d8f083bc61005d0a1ef592b149f5c88bbd ]

When clearing the .bss section in kernel_entry we do so using LONG_S
instructions, and branch whilst the current write address doesn't equal
the end of the .bss section minus the size of a long integer. The .bss
section always begins at a long-aligned address and we always increment
the write pointer by the size of a long integer - we therefore rely upon
the .bss section ending at a long-aligned address. If this is not the
case then the long-aligned write address can never be equal to the
non-long-aligned end address & we will continue to increment past the
end of the .bss section, attempting to zero the rest of memory.

Despite this requirement that .bss end at a long-aligned address we pass
0 as the end alignment requirement to the BSS_SECTION macro and thus
don't guarantee any particular alignment, allowing us to hit the error
condition described above.

Fix this by instead passing 8 bytes as the end alignment argument to
the BSS_SECTION macro, ensuring that the end of the .bss section is
always at least long-aligned.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14526/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/mips/kernel/vmlinux.lds.S |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -182,7 +182,7 @@ SECTIONS
 	 * Force .bss to 64K alignment so that .bss..swapper_pg_dir
 	 * gets that alignment.	 .sbss should be empty, so there will be
 	 * no holes after __init_end. */
-	BSS_SECTION(0, 0x10000, 0)
+	BSS_SECTION(0, 0x10000, 8)
 
 	_end = . ;
 


Patches currently in stable-queue which might be from paul.burton@imgtec.com are

queue-4.9/mips-irq-stack-unwind-irq-stack-onto-task-stack.patch
queue-4.9/mips-smp-cps-fix-retrieval-of-vpe-mask-on-big-endian-cpus.patch
queue-4.9/mips-ensure-bss-section-ends-on-a-long-aligned-address.patch