[PATCH 5.15.y] s390/entry: Fix last breaking event handling in case of stack corruption

[PATCH 5.15.y] s390/entry: Fix last breaking event handling in case of stack corruption

[Heiko Carstens]

commit ae952eea6f4a7e2193f8721a5366049946e012e7 upstream.

Note: the GET_LC macro and all the infrastructe that comes with this does
not exist for this kernel release. Therefore the patch is slightly
different to the upstream variant.

In case of stack corruption stack_invalid() is called and the expectation
is that register r10 contains the last breaking event address. This
dependency is quite subtle and broke a couple of years ago without that
anybody noticed.

Fix this by getting rid of the dependency and read the last breaking event
address from lowcore.

Fixes: 56e62a737028 ("s390: convert to generic entry")
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/kernel/entry.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 160290049e8c..14a5eff4d027 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -676,7 +676,7 @@ ENTRY(stack_overflow)
 	stmg	%r0,%r7,__PT_R0(%r11)
 	stmg	%r8,%r9,__PT_PSW(%r11)
 	mvc	__PT_R8(64,%r11),0(%r14)
-	stg	%r10,__PT_ORIG_GPR2(%r11) # store last break to orig_gpr2
+	mvc	__PT_ORIG_GPR2(8,%r11),__LC_LAST_BREAK
 	xc	__SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
 	lgr	%r2,%r11		# pass pointer to pt_regs
 	jg	kernel_stack_overflow
-- 
2.48.1

Re: [PATCH 5.15.y] s390/entry: Fix last breaking event handling in case of stack corruption

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: ae952eea6f4a7e2193f8721a5366049946e012e7

Status in newer kernel trees:
6.15.y | Present (exact SHA1)
6.12.y | Present (different SHA1: 5c3b8f05756b)
6.6.y | Not found
6.1.y | Not found

Note: The patch differs from the upstream commit:
---
1:  ae952eea6f4a7 < -:  ------------- s390/entry: Fix last breaking event handling in case of stack corruption
-:  ------------- > 1:  16cf896acf5e0 s390/entry: Fix last breaking event handling in case of stack corruption
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |