linux-kernel - [RFC][PATCH 20/22] x86: x32_setup_rt_frame(): consolidate uaccess areas

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Message-Id: <20200323183819.250124-20-viro@ZenIV.linux.org.uk>
Date:   Mon, 23 Mar 2020 18:38:17 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [RFC][PATCH 20/22] x86: x32_setup_rt_frame(): consolidate uaccess areas

From: Al Viro <viro@...iv.linux.org.uk>

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 arch/x86/kernel/signal.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 66bcb5539ae7..50679e8f42d7 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -514,7 +514,6 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
 	struct rt_sigframe_x32 __user *frame;
 	unsigned long uc_flags;
 	void __user *restorer;
-	int err = 0;
 	void __user *fpstate = NULL;
 
 	if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
@@ -522,14 +521,6 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
 
 	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 
-	if (!access_ok(frame, sizeof(*frame)))
-		return -EFAULT;
-
-	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
-		if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
-			return -EFAULT;
-	}
-
 	uc_flags = frame_uc_flags(regs);
 
 	if (!user_access_begin(frame, sizeof(*frame)))
@@ -545,11 +536,13 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
 	if (setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 				regs, set->sig[0]))
 		goto Efault;
+	unsafe_put_user(*(__u64 *)set, (__u64 __user *)&frame->uc.uc_sigmask, Efault);
 	user_access_end();
-	err |= __put_user(*(__u64 *)set, (__u64 __user *)&frame->uc.uc_sigmask);
 
-	if (err)
-		return -EFAULT;
+	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
+		if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
+			return -EFAULT;
+	}
 
 	/* Set up registers for signal handler */
 	regs->sp = (unsigned long) frame;
-- 
2.11.0