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| author | Thomas Gleixner <tglx@linutronix.de> | 2022-09-15 13:10:43 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-10-17 16:40:56 +0200 |
| commit | 2cb15faaedeb67f52f2ddc32b5ca152acfc422c2 (patch) | |
| tree | 3285155905adb263c0d1baae94872f622de23cf7 | |
| parent | 1f19e2d50baf6515991844eaa8a84a0b0037da70 (diff) | |
| download | lwn-2cb15faaedeb67f52f2ddc32b5ca152acfc422c2.tar.gz lwn-2cb15faaedeb67f52f2ddc32b5ca152acfc422c2.zip | |
x86/cpu: Re-enable stackprotector
Commit 5416c2663517 ("x86: make sure load_percpu_segment has no
stackprotector") disabled the stackprotector for cpu/common.c because of
load_percpu_segment(). Back then the boot stack canary was initialized very
early in start_kernel(). Switching the per CPU area by loading the GDT
caused the stackprotector to fail with paravirt enabled kernels as the
GSBASE was not updated yet. In hindsight a wrong change because it would
have been sufficient to ensure that the canary is the same in both per CPU
areas.
Commit d55535232c3d ("random: move rand_initialize() earlier") moved the
stack canary initialization to a later point in the init sequence. As a
consequence the per CPU stack canary is 0 when switching the per CPU areas,
so there is no requirement anymore to exclude this file.
Add a comment to load_percpu_segment().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111143.303010511@infradead.org
| -rw-r--r-- | arch/x86/kernel/cpu/Makefile | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 3 |
2 files changed, 3 insertions, 3 deletions
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile index f10a921ee756..d7e3ceaf75c1 100644 --- a/arch/x86/kernel/cpu/Makefile +++ b/arch/x86/kernel/cpu/Makefile @@ -17,9 +17,6 @@ KMSAN_SANITIZE_common.o := n # As above, instrumenting secondary CPU boot code causes boot hangs. KCSAN_SANITIZE_common.o := n -# Make sure load_percpu_segment has no stackprotector -CFLAGS_common.o := -fno-stack-protector - obj-y := cacheinfo.o scattered.o topology.o obj-y += common.o obj-y += rdrand.o diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index f51928dd275a..8e873181759a 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -752,6 +752,9 @@ void __init switch_gdt_and_percpu_base(int cpu) * early mapping is still valid. That means the GSBASE update will * lose any prior per CPU data which was not copied over in * setup_per_cpu_areas(). + * + * This works even with stackprotector enabled because the + * per CPU stack canary is 0 in both per CPU areas. */ wrmsrl(MSR_GS_BASE, cpu_kernelmode_gs_base(cpu)); #else |