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arm64: Change the tagged_addr sysctl control semantics to only prevent the opt-in 

First rename the sysctl control to abi.tagged_addr_disabled and make it
default off (zero). When abi.tagged_addr_disabled == 1, only block the
enabling of the TBI ABI via prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE).
Getting the status of the ABI or disabling it is still allowed.

Acked-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Catalin Marinas 2019-08-15 16:44:01 +01:00 committed by Will Deacon
parent 3e91ec89f5
commit 413235fced
1 changed files with 10 additions and 7 deletions
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17
arch/arm64/kernel/process.c
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@ -579,17 +579,22 @@ void arch_setup_new_exec(void)
/*
* Control the relaxed ABI allowing tagged user addresses into the kernel.
*/
static unsigned int tagged_addr_prctl_allowed = 1;
static unsigned int tagged_addr_disabled;
long set_tagged_addr_ctrl(unsigned long arg)
{
if (!tagged_addr_prctl_allowed)
return -EINVAL;
if (is_compat_task())
return -EINVAL;
if (arg & ~PR_TAGGED_ADDR_ENABLE)
return -EINVAL;
/*
* Do not allow the enabling of the tagged address ABI if globally
* disabled via sysctl abi.tagged_addr_disabled.
*/
if (arg & PR_TAGGED_ADDR_ENABLE && tagged_addr_disabled)
return -EINVAL;
update_thread_flag(TIF_TAGGED_ADDR, arg & PR_TAGGED_ADDR_ENABLE);
return 0;
@ -597,8 +602,6 @@ long set_tagged_addr_ctrl(unsigned long arg)
long get_tagged_addr_ctrl(void)
{
if (!tagged_addr_prctl_allowed)
return -EINVAL;
if (is_compat_task())
return -EINVAL;
@ -618,9 +621,9 @@ static int one = 1;
static struct ctl_table tagged_addr_sysctl_table[] = {
{
.procname = "tagged_addr",
.procname = "tagged_addr_disabled",
.mode = 0644,
.data = &tagged_addr_prctl_allowed,
.data = &tagged_addr_disabled,
.maxlen = sizeof(int),
.proc_handler = proc_dointvec_minmax,
.extra1 = &zero,