android/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

arm64: Stash shadow stack pointer in the task struct on interrupt

Browse Source 
commit 59b37fe52f49955791a460752c37145f1afdcad1 upstream.

Instead of reloading the shadow call stack pointer from the ordinary
stack, which may be vulnerable to the kind of gadget based attacks
shadow call stacks were designed to prevent, let's store a task's shadow
call stack pointer in the task struct when switching to the shadow IRQ
stack.

Given that currently, the task_struct::scs_sp field is only used to
preserve the shadow call stack pointer while a task is scheduled out or
running in user space, reusing this field to preserve and restore it
while running off the IRQ stack must be safe, as those occurrences are
guaranteed to never overlap. (The stack switching logic only switches
stacks when running from the task stack, and so the value being saved
here always corresponds to the task mode shadow stack)

While at it, fold a mov/add/mov sequence into a single add.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20230109174800.3286265-3-ardb@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ardb: v5.10 backport, which doesn't have call_on_irq_stack() yet *]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ard Biesheuvel 2023-01-09 18:48:00 +01:00 committed by Greg Kroah-Hartman
parent 9134b5a464
commit 3f225f29c6
1 changed files with 2 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/arm64/kernel/entry.S
View File

@ -431,9 +431,7 @@ SYM_CODE_END(__swpan_exit_el0)
.macro irq_stack_entry
mov x19, sp // preserve the original sp
#ifdef CONFIG_SHADOW_CALL_STACK
mov x24, scs_sp // preserve the original shadow stack
#endif
scs_save tsk // preserve the original shadow stack
/*
* Compare sp with the base of the task stack.
@ -467,9 +465,7 @@ SYM_CODE_END(__swpan_exit_el0)
*/
.macro irq_stack_exit
mov sp, x19
#ifdef CONFIG_SHADOW_CALL_STACK
mov scs_sp, x24
#endif
scs_load_current
.endm
/* GPRs used by entry code */