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arm64: reject prctl(PR_PAC_RESET_KEYS) on compat tasks

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It doesn't make sense to issue prctl(PR_PAC_RESET_KEYS) on a
compat task because the 32-bit instruction set does not offer PAuth
instructions. For consistency with other 64-bit only prctls such as
{SET,GET}_TAGGED_ADDR_CTRL, reject the prctl on compat tasks.

Although this is a userspace-visible change, maybe it isn't too late
to make this change given that the hardware isn't available yet and
it's very unlikely that anyone has 32-bit software that actually
depends on this succeeding.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Ie885a1ff84ab498cc9f62d6451e9f2cfd4b1d06a
Link: https://lore.kernel.org/r/20201014052430.11630-1-pcc@google.com
[will: Do the same for the SVE prctl()s]
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Peter Collingbourne 2020-10-13 22:24:30 -07:00 committed by Will Deacon
parent d13027bb35
commit 4b7a6ce71e
2 changed files with 6 additions and 2 deletions
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4
arch/arm64/kernel/fpsimd.c
View File

@ -678,7 +678,7 @@ int sve_set_current_vl(unsigned long arg)
vl = arg & PR_SVE_VL_LEN_MASK;
flags = arg & ~vl;
if (!system_supports_sve())
if (!system_supports_sve() || is_compat_task())
return -EINVAL;
ret = sve_set_vector_length(current, vl, flags);
@ -691,7 +691,7 @@ int sve_set_current_vl(unsigned long arg)
/* PR_SVE_GET_VL */
int sve_get_current_vl(void)
{
if (!system_supports_sve())
if (!system_supports_sve() || is_compat_task())
return -EINVAL;
return sve_prctl_status(0);

4
arch/arm64/kernel/pointer_auth.c
View File

@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/compat.h>
#include <linux/errno.h>
#include <linux/prctl.h>
#include <linux/random.h>
@ -17,6 +18,9 @@ int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
if (!system_supports_address_auth() && !system_supports_generic_auth())
return -EINVAL;
if (is_compat_thread(task_thread_info(tsk)))
return -EINVAL;
if (!arg) {
ptrauth_keys_init_user(keys);
return 0;