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Revision 8ec7791bae1327b1c279c5cd6e929c3b12daaf0a authored by Michael Ellerman on 06 May 2021, 04:49:58 UTC, committed by Michael Ellerman on 14 May 2021, 07:27:36 UTC 
powerpc/64s: Fix crashes when toggling stf barrier
 
The STF (store-to-load forwarding) barrier mitigation can be
enabled/disabled at runtime via a debugfs file (stf_barrier), which
causes the kernel to patch itself to enable/disable the relevant
mitigations.

However depending on which mitigation we're using, it may not be safe to
do that patching while other CPUs are active. For example the following
crash:

  User access of kernel address (c00000003fff5af0) - exploit attempt? (uid: 0)
  segfault (11) at c00000003fff5af0 nip 7fff8ad12198 lr 7fff8ad121f8 code 1
  code: 40820128 e93c00d0 e9290058 7c292840 40810058 38600000 4bfd9a81 e8410018
  code: 2c030006 41810154 3860ffb6 e9210098 <e94d8ff0> 7d295279 39400000 40820a3c

Shows that we returned to userspace without restoring the user r13
value, due to executing the partially patched STF exit code.

Fix it by doing the patching under stop machine. The CPUs that aren't
doing the patching will be spinning in the core of the stop machine
logic. That is currently sufficient for our purposes, because none of
the patching we do is to that code or anywhere in the vicinity.

Fixes: a048a07d7f45 ("powerpc/64s: Add support for a store forwarding barrier at kernel entry/exit")
Cc: stable@vger.kernel.org # v4.17+
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210506044959.1298123-1-mpe@ellerman.id.au
1 parent da3bb20
Raw File
aegis128-neon.c 
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2019 Linaro Ltd <ard.biesheuvel@linaro.org>
 */

#include <asm/cpufeature.h>
#include <asm/neon.h>

#include "aegis.h"

void crypto_aegis128_init_neon(void *state, const void *key, const void *iv);
void crypto_aegis128_update_neon(void *state, const void *msg);
void crypto_aegis128_encrypt_chunk_neon(void *state, void *dst, const void *src,
					unsigned int size);
void crypto_aegis128_decrypt_chunk_neon(void *state, void *dst, const void *src,
					unsigned int size);
int crypto_aegis128_final_neon(void *state, void *tag_xor,
			       unsigned int assoclen,
			       unsigned int cryptlen,
			       unsigned int authsize);

int aegis128_have_aes_insn __ro_after_init;

bool crypto_aegis128_have_simd(void)
{
	if (cpu_have_feature(cpu_feature(AES))) {
		aegis128_have_aes_insn = 1;
		return true;
	}
	return IS_ENABLED(CONFIG_ARM64);
}

void crypto_aegis128_init_simd(struct aegis_state *state,
			       const union aegis_block *key,
			       const u8 *iv)
{
	kernel_neon_begin();
	crypto_aegis128_init_neon(state, key, iv);
	kernel_neon_end();
}

void crypto_aegis128_update_simd(struct aegis_state *state, const void *msg)
{
	kernel_neon_begin();
	crypto_aegis128_update_neon(state, msg);
	kernel_neon_end();
}

void crypto_aegis128_encrypt_chunk_simd(struct aegis_state *state, u8 *dst,
					const u8 *src, unsigned int size)
{
	kernel_neon_begin();
	crypto_aegis128_encrypt_chunk_neon(state, dst, src, size);
	kernel_neon_end();
}

void crypto_aegis128_decrypt_chunk_simd(struct aegis_state *state, u8 *dst,
					const u8 *src, unsigned int size)
{
	kernel_neon_begin();
	crypto_aegis128_decrypt_chunk_neon(state, dst, src, size);
	kernel_neon_end();
}

int crypto_aegis128_final_simd(struct aegis_state *state,
			       union aegis_block *tag_xor,
			       unsigned int assoclen,
			       unsigned int cryptlen,
			       unsigned int authsize)
{
	int ret;

	kernel_neon_begin();
	ret = crypto_aegis128_final_neon(state, tag_xor, assoclen, cryptlen,
					 authsize);
	kernel_neon_end();

	return ret;
}
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