[PATCH v8 3/5] arm64: Change the tagged_addr sysctl control semantics to only prevent the opt-in
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2019-08-15 15:44:18
Also in:
linux-arch, linux-doc, linux-mm
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/kernel/process.c | 17 ++++++++++------- 1 file 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,
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