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authorCatalin Marinas <catalin.marinas@arm.com>2019-08-15 16:44:01 +0100
committerWill Deacon <will@kernel.org>2019-08-20 18:18:10 +0100
commit413235fcedc7f61e925fe9818bc3f5eff8ad2494 (patch)
tree0c863fbe6a6cdb9cee727f52e5ae8cee565751ef /arch/arm64/kernel
parent3e91ec89f527b9870fe42dcbdb74fd389d123a95 (diff)
downloadlinux-413235fcedc7f61e925fe9818bc3f5eff8ad2494.tar.bz2
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>
Diffstat (limited to 'arch/arm64/kernel')
-rw-r--r--arch/arm64/kernel/process.c17
1 files changed, 10 insertions, 7 deletions
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 76b7c55026aa..03689c0beb34 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -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,