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
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

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Raw File
ripemd.h
/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Common values for RIPEMD algorithms
 */

#ifndef _CRYPTO_RMD_H
#define _CRYPTO_RMD_H

#define RMD160_DIGEST_SIZE      20
#define RMD160_BLOCK_SIZE       64

/* initial values  */
#define RMD_H0  0x67452301UL
#define RMD_H1  0xefcdab89UL
#define RMD_H2  0x98badcfeUL
#define RMD_H3  0x10325476UL
#define RMD_H4  0xc3d2e1f0UL

/* constants */
#define RMD_K1  0x00000000UL
#define RMD_K2  0x5a827999UL
#define RMD_K3  0x6ed9eba1UL
#define RMD_K4  0x8f1bbcdcUL
#define RMD_K5  0xa953fd4eUL
#define RMD_K6  0x50a28be6UL
#define RMD_K7  0x5c4dd124UL
#define RMD_K8  0x6d703ef3UL
#define RMD_K9  0x7a6d76e9UL

#endif
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