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| author | James Morse <james.morse@arm.com> | 2016-10-18 11:27:47 +0100 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2016-10-20 09:50:53 +0100 |
| commit | 7209c868600bd8926e37c10b9aae83124ccc1dd8 (patch) | |
| tree | 39995a8ef78a77bd77b9897da57c5b81aeba27f4 | |
| parent | 2a6dcb2b5f3e21592ca8dfa198dcce7bec09b020 (diff) | |
| download | linux-7209c868600bd8926e37c10b9aae83124ccc1dd8.tar.gz | |
arm64: mm: Set PSTATE.PAN from the cpu_enable_pan() call
Commit 338d4f49d6f7 ("arm64: kernel: Add support for Privileged Access
Never") enabled PAN by enabling the 'SPAN' feature-bit in SCTLR_EL1.
This means the PSTATE.PAN bit won't be set until the next return to the
kernel from userspace. On a preemptible kernel we may schedule work that
accesses userspace on a CPU before it has done this.
Now that cpufeature enable() calls are scheduled via stop_machine(), we
can set PSTATE.PAN from the cpu_enable_pan() call.
Add WARN_ON_ONCE(in_interrupt()) to check the PSTATE value we updated
is not immediately discarded.
Reported-by: Tony Thompson <anthony.thompson@arm.com>
Reported-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
[will: fixed typo in comment]
Signed-off-by: Will Deacon <will.deacon@arm.com>
| -rw-r--r-- | arch/arm64/mm/fault.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 3e9ff9b0c78d56..0f87883748153b 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -29,7 +29,9 @@ #include <linux/sched.h> #include <linux/highmem.h> #include <linux/perf_event.h> +#include <linux/preempt.h> +#include <asm/bug.h> #include <asm/cpufeature.h> #include <asm/exception.h> #include <asm/debug-monitors.h> @@ -672,7 +674,14 @@ NOKPROBE_SYMBOL(do_debug_exception); #ifdef CONFIG_ARM64_PAN int cpu_enable_pan(void *__unused) { + /* + * We modify PSTATE. This won't work from irq context as the PSTATE + * is discarded once we return from the exception. + */ + WARN_ON_ONCE(in_interrupt()); + config_sctlr_el1(SCTLR_EL1_SPAN, 0); + asm(SET_PSTATE_PAN(1)); return 0; } #endif /* CONFIG_ARM64_PAN */ |