[PATCH 3.16 113/366] zboot: fix stack protector in compressed boot phase

[Ben Hutchings]

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Huacai Chen <chenhc@xxxxxxxxxx>

commit 7bbaf27d9c83037b6e60a818e57bdbedf6bc15be upstream.

Calling __stack_chk_guard_setup() in decompress_kernel() is too late
that stack checking always fails for decompress_kernel() itself.  So
remove __stack_chk_guard_setup() and initialize __stack_chk_guard before
we call decompress_kernel().

Original code comes from ARM but also used for MIPS and SH, so fix them
together.  If without this fix, compressed booting of these archs will
fail because stack checking is enabled by default (>=4.16).

Link: http://lkml.kernel.org/r/1522226933-29317-1-git-send-email-chenhc@xxxxxxxxxx
Fixes: 8779657d29c0 ("stackprotector: Introduce CONFIG_CC_STACKPROTECTOR_STRONG")
Signed-off-by: Huacai Chen <chenhc@xxxxxxxxxx>
Acked-by: James Hogan <jhogan@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Rich Felker <dalias@xxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16: Only ARM has this problem]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/arch/arm/boot/compressed/misc.c
+++ b/arch/arm/boot/compressed/misc.c
@@ -127,12 +127,7 @@ asmlinkage void __div0(void)
 	error("Attempting division by 0!");
 }
 
-unsigned long __stack_chk_guard;
-
-void __stack_chk_guard_setup(void)
-{
-	__stack_chk_guard = 0x000a0dff;
-}
+const unsigned long __stack_chk_guard = 0x000a0dff;
 
 void __stack_chk_fail(void)
 {
@@ -149,8 +144,6 @@ decompress_kernel(unsigned long output_s
 {
 	int ret;
 
-	__stack_chk_guard_setup();
-
 	output_data		= (unsigned char *)output_start;
 	free_mem_ptr		= free_mem_ptr_p;
 	free_mem_end_ptr	= free_mem_ptr_end_p;