? 2018-03-22?? 22:21 +0000?James Hogan???

On Fri, Mar 16, 2018 at 03:55:16PM +0800, Huacai Chen wrote:

quoted

diff --git a/arch/mips/boot/compressed/decompress.c

b/arch/mips/boot/compressed/decompress.c
index fdf99e9..5ba431c 100644

--- a/arch/mips/boot/compressed/decompress.c
+++ b/arch/mips/boot/compressed/decompress.c

@@ -78,11 +78,6 @@ void error(char *x)
 
 unsigned long __stack_chk_guard;

...

quoted

diff --git a/arch/mips/boot/compressed/head.S

b/arch/mips/boot/compressed/head.S
index 409cb48..00d0ee0 100644

--- a/arch/mips/boot/compressed/head.S
+++ b/arch/mips/boot/compressed/head.S

@@ -32,6 +32,10 @@ start:
 	bne	a2, a0, 1b
 	 addiu	a0, a0, 4
 
+	PTR_LA	a0, __stack_chk_guard
+	PTR_LI	a1, 0x000a0dff
+	sw	a1, 0(a0)

Hi James

Huacai Can't reply this mail. His chenhc at lemote.com is blcoked by
Linux-MIPS mailing list while his Gmail didn't receive this email, so
I'm replying for him.

Should that not be LONG_S? Otherwise big endian MIPS64 would get a
word-swapped canary (which is probably mostly harmless, but still).

Yes, he said it's considerable.

Also I think it worth mentioning in the commit message the MIPS
configuration you hit this with, presumably a Loongson one? For me
decompress_kernel() gets a stack guard on loongson3_defconfig, but
not
malta_defconfig or malta_defconfig + 64-bit. I presume its sensitive
to
the compiler inlining stuff into decompress_kernel() or something
such
that it suddenly qualifies for a stack guard.

Have you tested with CONFIG_CC_STACKPROTECTOR_STRONG=y ?
Huacai reproduced the issue by this[1] config with GCC 4.9.

[1] https://github.com/loongson-community/linux-stable/blob/rebase-4.14
/arch/mips/configs/loongson3_defconfig

Cheers
James