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
1 parent da3bb20
rsa_helper.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* RSA key extract helper
*
* Copyright (c) 2015, Intel Corporation
* Authors: Tadeusz Struk <tadeusz.struk@intel.com>
*/
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/err.h>
#include <linux/fips.h>
#include <crypto/internal/rsa.h>
#include "rsapubkey.asn1.h"
#include "rsaprivkey.asn1.h"
int rsa_get_n(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
const u8 *ptr = value;
size_t n_sz = vlen;
/* invalid key provided */
if (!value || !vlen)
return -EINVAL;
if (fips_enabled) {
while (n_sz && !*ptr) {
ptr++;
n_sz--;
}
/* In FIPS mode only allow key size 2K and higher */
if (n_sz < 256) {
pr_err("RSA: key size not allowed in FIPS mode\n");
return -EINVAL;
}
}
key->n = value;
key->n_sz = vlen;
return 0;
}
int rsa_get_e(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
/* invalid key provided */
if (!value || !key->n_sz || !vlen || vlen > key->n_sz)
return -EINVAL;
key->e = value;
key->e_sz = vlen;
return 0;
}
int rsa_get_d(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
/* invalid key provided */
if (!value || !key->n_sz || !vlen || vlen > key->n_sz)
return -EINVAL;
key->d = value;
key->d_sz = vlen;
return 0;
}
int rsa_get_p(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
/* invalid key provided */
if (!value || !vlen || vlen > key->n_sz)
return -EINVAL;
key->p = value;
key->p_sz = vlen;
return 0;
}
int rsa_get_q(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
/* invalid key provided */
if (!value || !vlen || vlen > key->n_sz)
return -EINVAL;
key->q = value;
key->q_sz = vlen;
return 0;
}
int rsa_get_dp(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
/* invalid key provided */
if (!value || !vlen || vlen > key->n_sz)
return -EINVAL;
key->dp = value;
key->dp_sz = vlen;
return 0;
}
int rsa_get_dq(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
/* invalid key provided */
if (!value || !vlen || vlen > key->n_sz)
return -EINVAL;
key->dq = value;
key->dq_sz = vlen;
return 0;
}
int rsa_get_qinv(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
/* invalid key provided */
if (!value || !vlen || vlen > key->n_sz)
return -EINVAL;
key->qinv = value;
key->qinv_sz = vlen;
return 0;
}
/**
* rsa_parse_pub_key() - decodes the BER encoded buffer and stores in the
* provided struct rsa_key, pointers to the raw key as is,
* so that the caller can copy it or MPI parse it, etc.
*
* @rsa_key: struct rsa_key key representation
* @key: key in BER format
* @key_len: length of key
*
* Return: 0 on success or error code in case of error
*/
int rsa_parse_pub_key(struct rsa_key *rsa_key, const void *key,
unsigned int key_len)
{
return asn1_ber_decoder(&rsapubkey_decoder, rsa_key, key, key_len);
}
EXPORT_SYMBOL_GPL(rsa_parse_pub_key);
/**
* rsa_parse_priv_key() - decodes the BER encoded buffer and stores in the
* provided struct rsa_key, pointers to the raw key
* as is, so that the caller can copy it or MPI parse it,
* etc.
*
* @rsa_key: struct rsa_key key representation
* @key: key in BER format
* @key_len: length of key
*
* Return: 0 on success or error code in case of error
*/
int rsa_parse_priv_key(struct rsa_key *rsa_key, const void *key,
unsigned int key_len)
{
return asn1_ber_decoder(&rsaprivkey_decoder, rsa_key, key, key_len);
}
EXPORT_SYMBOL_GPL(rsa_parse_priv_key);
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