Commit 76721503 authored by Mark Rutland's avatar Mark Rutland Committed by Catalin Marinas
Browse files

arm64: kasan: mte: remove redundant mte_report_once logic 



We have special logic to suppress MTE tag check fault reporting, based
on a global `mte_report_once` and `reported` variables. These can be
used to suppress calling kasan_report() when taking a tag check fault,
but do not prevent taking the fault in the first place, nor does they
affect the way we disable tag checks upon taking a fault.

The core KASAN code already defaults to reporting a single fault, and
has a `multi_shot` control to permit reporting multiple faults. The only
place we transiently alter `mte_report_once` is in lib/test_kasan.c,
where we also the `multi_shot` state as the same time. Thus
`mte_report_once` and `reported` are redundant, and can be removed.

When a tag check fault is taken, tag checking will be disabled by
`do_tag_recovery` and must be explicitly re-enabled if desired. The test
code does this by calling kasan_enable_tagging_sync().

This patch removes the redundant mte_report_once() logic and associated
variables.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: default avatarAndrey Konovalov <andreyknvl@gmail.com>
Tested-by: default avatarAndrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20210714143843.56537-4-mark.rutland@arm.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 82868247

arch/arm64/include/asm/memory.h

+0 −1
Original line number Diff line number Diff line
@@ -243,7 +243,6 @@ static inline const void *__tag_set(const void *addr, u8 tag) 
#ifdef CONFIG_KASAN_HW_TAGS

#define arch_enable_tagging_sync()		mte_enable_kernel_sync()

#define arch_enable_tagging_async()		mte_enable_kernel_async()

#define arch_set_tagging_report_once(state)	mte_set_report_once(state)

#define arch_force_async_tag_fault()		mte_check_tfsr_exit()

#define arch_get_random_tag()			mte_get_random_tag()

#define arch_get_mem_tag(addr)			mte_get_mem_tag(addr)

arch/arm64/include/asm/mte-kasan.h

+0 −12
Original line number Diff line number Diff line
@@ -131,9 +131,6 @@ static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag, 
void mte_enable_kernel_sync(void);

void mte_enable_kernel_async(void);



void mte_set_report_once(bool state);

bool mte_report_once(void);



#else /* CONFIG_ARM64_MTE */



static inline u8 mte_get_ptr_tag(void *ptr)
@@ -164,15 +161,6 @@ static inline void mte_enable_kernel_async(void) 
{

}



static inline void mte_set_report_once(bool state)

{

}



static inline bool mte_report_once(void)

{

	return false;

}



#endif /* CONFIG_ARM64_MTE */



#endif /* __ASSEMBLY__ */

arch/arm64/kernel/mte.c

+0 −12
Original line number Diff line number Diff line
@@ -23,8 +23,6 @@ 
#include <asm/ptrace.h>

#include <asm/sysreg.h>



static bool report_fault_once = true;



static DEFINE_PER_CPU_READ_MOSTLY(u64, mte_tcf_preferred);



#ifdef CONFIG_KASAN_HW_TAGS
@@ -141,16 +139,6 @@ void mte_enable_kernel_async(void) 
}

#endif



void mte_set_report_once(bool state)

{

	WRITE_ONCE(report_fault_once, state);

}



bool mte_report_once(void)

{

	return READ_ONCE(report_fault_once);

}



#ifdef CONFIG_KASAN_HW_TAGS

void mte_check_tfsr_el1(void)

{

arch/arm64/mm/fault.c

+1 −14
Original line number Diff line number Diff line
@@ -309,24 +309,11 @@ static void die_kernel_fault(const char *msg, unsigned long addr, 
static void report_tag_fault(unsigned long addr, unsigned int esr,

			     struct pt_regs *regs)

{

	static bool reported;

	bool is_write;



	if (READ_ONCE(reported))

		return;



	/*

	 * This is used for KASAN tests and assumes that no MTE faults

	 * happened before running the tests.

	 */

	if (mte_report_once())

		WRITE_ONCE(reported, true);



	/*

	 * SAS bits aren't set for all faults reported in EL1, so we can't

	 * find out access size.

	 */

	is_write = !!(esr & ESR_ELx_WNR);

	bool is_write = !!(esr & ESR_ELx_WNR);

	kasan_report(addr, 0, is_write, regs->pc);

}

#else

lib/test_kasan.c

+0 −2
Original line number Diff line number Diff line
@@ -53,7 +53,6 @@ static int kasan_test_init(struct kunit *test) 
	}



	multishot = kasan_save_enable_multi_shot();

	kasan_set_tagging_report_once(false);

	fail_data.report_found = false;

	kunit_add_named_resource(test, NULL, NULL, &resource,

					"kasan_data", &fail_data);
@@ -62,7 +61,6 @@ static int kasan_test_init(struct kunit *test) 


static void kasan_test_exit(struct kunit *test)

{

	kasan_set_tagging_report_once(true);

	kasan_restore_multi_shot(multishot);

	KUNIT_EXPECT_FALSE(test, fail_data.report_found);

}