linux-kernel - [PATCH] x86/prctl: Remove pointless task argument

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Message-ID: <87lev7vtxj.ffs@tglx>
Date:   Thu, 12 May 2022 14:04:08 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "H . J. Lu" <hjl.tools@...il.com>, Andi Kleen <ak@...ux.intel.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH] x86/prctl: Remove pointless task argument

The functions invoked via do_arch_prctl_common() can only operate on
the current task and none of these function uses the task argument.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/include/asm/fpu/api.h |    3 +--
 arch/x86/include/asm/proto.h   |    3 +--
 arch/x86/kernel/fpu/xstate.c   |    5 +----
 arch/x86/kernel/process.c      |    9 ++++-----
 arch/x86/kernel/process_32.c   |    2 +-
 arch/x86/kernel/process_64.c   |    4 ++--
 6 files changed, 10 insertions(+), 16 deletions(-)

--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -162,7 +162,6 @@ static inline bool fpstate_is_confidenti
 }
 
 /* prctl */
-struct task_struct;
-extern long fpu_xstate_prctl(struct task_struct *tsk, int option, unsigned long arg2);
+extern long fpu_xstate_prctl(int option, unsigned long arg2);
 
 #endif /* _ASM_X86_FPU_API_H */
--- a/arch/x86/include/asm/proto.h
+++ b/arch/x86/include/asm/proto.h
@@ -38,7 +38,6 @@ void x86_configure_nx(void);
 
 extern int reboot_force;
 
-long do_arch_prctl_common(struct task_struct *task, int option,
-			  unsigned long arg2);
+long do_arch_prctl_common(int option, unsigned long arg2);
 
 #endif /* _ASM_X86_PROTO_H */
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1705,16 +1705,13 @@ EXPORT_SYMBOL_GPL(xstate_get_guest_group
  * e.g. for AMX which requires XFEATURE_XTILE_CFG(17) and
  * XFEATURE_XTILE_DATA(18) this would be XFEATURE_XTILE_DATA(18).
  */
-long fpu_xstate_prctl(struct task_struct *tsk, int option, unsigned long arg2)
+long fpu_xstate_prctl(int option, unsigned long arg2)
 {
 	u64 __user *uptr = (u64 __user *)arg2;
 	u64 permitted, supported;
 	unsigned long idx = arg2;
 	bool guest = false;
 
-	if (tsk != current)
-		return -EPERM;
-
 	switch (option) {
 	case ARCH_GET_XCOMP_SUPP:
 		supported = fpu_user_cfg.max_features |	fpu_user_cfg.legacy_features;
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -332,7 +332,7 @@ static int get_cpuid_mode(void)
 	return !test_thread_flag(TIF_NOCPUID);
 }
 
-static int set_cpuid_mode(struct task_struct *task, unsigned long cpuid_enabled)
+static int set_cpuid_mode(unsigned long cpuid_enabled)
 {
 	if (!boot_cpu_has(X86_FEATURE_CPUID_FAULT))
 		return -ENODEV;
@@ -983,20 +983,19 @@ unsigned long __get_wchan(struct task_st
 	return addr;
 }
 
-long do_arch_prctl_common(struct task_struct *task, int option,
-			  unsigned long arg2)
+long do_arch_prctl_common(int option, unsigned long arg2)
 {
 	switch (option) {
 	case ARCH_GET_CPUID:
 		return get_cpuid_mode();
 	case ARCH_SET_CPUID:
-		return set_cpuid_mode(task, arg2);
+		return set_cpuid_mode(arg2);
 	case ARCH_GET_XCOMP_SUPP:
 	case ARCH_GET_XCOMP_PERM:
 	case ARCH_REQ_XCOMP_PERM:
 	case ARCH_GET_XCOMP_GUEST_PERM:
 	case ARCH_REQ_XCOMP_GUEST_PERM:
-		return fpu_xstate_prctl(task, option, arg2);
+		return fpu_xstate_prctl(option, arg2);
 	}
 
 	return -EINVAL;
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -219,5 +219,5 @@ EXPORT_SYMBOL_GPL(start_thread);
 
 SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
 {
-	return do_arch_prctl_common(current, option, arg2);
+	return do_arch_prctl_common(option, arg2);
 }
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -844,7 +844,7 @@ SYSCALL_DEFINE2(arch_prctl, int, option,
 
 	ret = do_arch_prctl_64(current, option, arg2);
 	if (ret == -EINVAL)
-		ret = do_arch_prctl_common(current, option, arg2);
+		ret = do_arch_prctl_common(option, arg2);
 
 	return ret;
 }
@@ -852,7 +852,7 @@ SYSCALL_DEFINE2(arch_prctl, int, option,
 #ifdef CONFIG_IA32_EMULATION
 COMPAT_SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
 {
-	return do_arch_prctl_common(current, option, arg2);
+	return do_arch_prctl_common(option, arg2);
 }
 #endif