[PATCH v4 1/8] arm64/gcs: task_gcs_el0_enable() should use passed task
From: Jeremy Linton <hidden>
Date: 2025-07-19 04:37:53
Also in:
linux-arm-kernel, linux-perf-users, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
Mark Rutland noticed that the task parameter is ignored and
'current' is being used instead. Since this is usually
what its passed, it hasn't yet been causing problems but likely
will as the code gets more testing.
But, once this is fixed, it creates a new bug in copy_thread_gcs()
since the gcs_el_mode isn't yet set for the task before its being
checked. Move gcs_alloc_thread_stack() after the new task's
gcs_el0_mode initialization to avoid this.
Fixes: fc84bc5378a8 ("arm64/gcs: Context switch GCS state for EL0")
Signed-off-by: Jeremy Linton <redacted>
Reviewed-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/include/asm/gcs.h | 2 +-
arch/arm64/kernel/process.c | 6 +++---
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/gcs.h b/arch/arm64/include/asm/gcs.h
index f50660603ecf..5bc432234d3a 100644
--- a/arch/arm64/include/asm/gcs.h
+++ b/arch/arm64/include/asm/gcs.h@@ -58,7 +58,7 @@ static inline u64 gcsss2(void) static inline bool task_gcs_el0_enabled(struct task_struct *task) { - return current->thread.gcs_el0_mode & PR_SHADOW_STACK_ENABLE; + return task->thread.gcs_el0_mode & PR_SHADOW_STACK_ENABLE; } void gcs_set_el0_mode(struct task_struct *task);
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 08b7042a2e2d..3e1baff5e88d 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c@@ -307,13 +307,13 @@ static int copy_thread_gcs(struct task_struct *p, p->thread.gcs_base = 0; p->thread.gcs_size = 0; + p->thread.gcs_el0_mode = current->thread.gcs_el0_mode; + p->thread.gcs_el0_locked = current->thread.gcs_el0_locked; + gcs = gcs_alloc_thread_stack(p, args); if (IS_ERR_VALUE(gcs)) return PTR_ERR((void *)gcs); - p->thread.gcs_el0_mode = current->thread.gcs_el0_mode; - p->thread.gcs_el0_locked = current->thread.gcs_el0_locked; - return 0; }
--
2.50.1