[PATCH 5.18 59/61] x86/kexec: Disable RET on kexec

Greg Kroah-Hartman
2022-07-12T19:15:11Z

From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

commit 697977d8415d61f3acbc4ee6d564c9dcf0309507 upstream.

All the invocations unroll to __x86_return_thunk and this file
must be PIC independent.

This fixes kexec on 64-bit AMD boxes.

[ bp: Fix 32-bit build. ]

Reported-by: Edward Tran <edward.tran@oracle.com>
Reported-by: Awais Tanveer <awais.tanveer@oracle.com>
Suggested-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/relocate_kernel_32.S | 25 +++++++++++++++++++------
arch/x86/kernel/relocate_kernel_64.S | 23 +++++++++++++++++------
2 files changed, 36 insertions(+), 12 deletions(-)

--- a/arch/x86/kernel/relocate_kernel_32.S
+++ b/arch/x86/kernel/relocate_kernel_32.S
@@ -7,10 +7,12 @@
#include <linux/linkage.h>
#include <asm/page_types.h>
#include <asm/kexec.h>
+#include <asm/nospec-branch.h>
#include <asm/processor-flags.h>

/*
- * Must be relocatable PIC code callable as a C function
+ * Must be relocatable PIC code callable as a C function, in particular
+ * there must be a plain RET and not jump to return thunk.
*/

#define PTR(x) (x << 2)
@@ -91,7 +93,9 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
movl %edi, %eax
addl $(identity_mapped - relocate_kernel), %eax
pushl %eax
- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
SYM_CODE_END(relocate_kernel)

SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
@@ -159,12 +163,15 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_ma
xorl %edx, %edx
xorl %esi, %esi
xorl %ebp, %ebp
- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
1:
popl %edx
movl CP_PA_SWAP_PAGE(%edi), %esp
addl $PAGE_SIZE, %esp
2:
+ ANNOTATE_RETPOLINE_SAFE
call *%edx

/* get the re-entry point of the peer system */
@@ -190,7 +197,9 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_ma
movl %edi, %eax
addl $(virtual_mapped - relocate_kernel), %eax
pushl %eax
- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
SYM_CODE_END(identity_mapped)

SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
@@ -208,7 +217,9 @@ SYM_CODE_START_LOCAL_NOALIGN(virtual_map
popl %edi
popl %esi
popl %ebx
- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
SYM_CODE_END(virtual_mapped)

/* Do the copies */
@@ -271,7 +282,9 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
popl %edi
popl %ebx
popl %ebp
- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
SYM_CODE_END(swap_pages)

.globl kexec_control_code_size
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -13,7 +13,8 @@
#include <asm/unwind_hints.h>

/*
- * Must be relocatable PIC code callable as a C function
+ * Must be relocatable PIC code callable as a C function, in particular
+ * there must be a plain RET and not jump to return thunk.
*/

#define PTR(x) (x << 3)
@@ -105,7 +106,9 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
/* jump to identity mapped page */
addq $(identity_mapped - relocate_kernel), %r8
pushq %r8
- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
SYM_CODE_END(relocate_kernel)

SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
@@ -200,7 +203,9 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_ma
xorl %r14d, %r14d
xorl %r15d, %r15d

- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3

1:
popq %rdx
@@ -219,7 +224,9 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_ma
call swap_pages
movq $virtual_mapped, %rax
pushq %rax
- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
SYM_CODE_END(identity_mapped)

SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
@@ -241,7 +248,9 @@ SYM_CODE_START_LOCAL_NOALIGN(virtual_map
popq %r12
popq %rbp
popq %rbx
- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
SYM_CODE_END(virtual_mapped)

/* Do the copies */
@@ -298,7 +307,9 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
lea PAGE_SIZE(%rax), %rsi
jmp 0b
3:
- RET
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
SYM_CODE_END(swap_pages)

.globl kexec_control_code_size