linux-kernel - [PATCH] x86/fpu: Replace vmalloc + copy_from_user with vmemdup_user in xstateregs

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Message-ID: <20250917100536.57810-1-thorsten.blum@linux.dev>
Date: Wed, 17 Sep 2025 12:05:34 +0200
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc: Thorsten Blum <thorsten.blum@...ux.dev>,
	Ingo Molnar <mingo@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] x86/fpu: Replace vmalloc + copy_from_user with vmemdup_user in xstateregs_set

Replace vmalloc() followed by copy_from_user() with vmemdup_user() to
improve and simplify xstateregs_set(). Use kvfree() to free.

Return early if an error occurs and remove the obsolete 'out' label.

No functional changes intended.

Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
---
 arch/x86/kernel/fpu/regset.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c
index 0986c2200adc..00cc009918e6 100644
--- a/arch/x86/kernel/fpu/regset.c
+++ b/arch/x86/kernel/fpu/regset.c
@@ -3,6 +3,7 @@
  * FPU register's regset abstraction, for ptrace, core dumps, etc.
  */
 #include <linux/sched/task_stack.h>
+#include <linux/string.h>
 #include <linux/vmalloc.h>
 
 #include <asm/fpu/api.h>
@@ -157,21 +158,15 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
 		return -EFAULT;
 
 	if (!kbuf) {
-		tmpbuf = vmalloc(count);
-		if (!tmpbuf)
-			return -ENOMEM;
-
-		if (copy_from_user(tmpbuf, ubuf, count)) {
-			ret = -EFAULT;
-			goto out;
-		}
+		tmpbuf = vmemdup_user(ubuf, count);
+		if (IS_ERR(tmpbuf))
+			return PTR_ERR(tmpbuf);
 	}
 
 	fpu_force_restore(fpu);
 	ret = copy_uabi_from_kernel_to_xstate(fpu->fpstate, kbuf ?: tmpbuf, &target->thread.pkru);
 
-out:
-	vfree(tmpbuf);
+	kvfree(tmpbuf);
 	return ret;
 }
 
-- 
2.51.0