linux-kernel - [PATCH 8/8] waitid(): switch copyout of siginfo to unsafe_put

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Date:   Mon, 15 May 2017 23:37:16 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     linux-kernel@...r.kernel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Christoph Hellwig <hch@....de>
Subject: [PATCH 8/8] waitid(): switch copyout of siginfo to unsafe_put_user()

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

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 kernel/exit.c | 40 +++++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index e93876b06b28..a13dd4d0dc34 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1625,15 +1625,18 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
 	if (!infop)
 		return err;
 
-	if (put_user(err ? 0 : SIGCHLD, &infop->si_signo) ||
-	    put_user(0, &infop->si_errno) ||
-	    put_user((short)info.why, &infop->si_code) ||
-	    put_user(info.pid, &infop->si_pid) ||
-	    put_user(info.uid, &infop->si_uid) ||
-	    put_user(info.status, &infop->si_status))
-		err = -EFAULT;
-
+	user_access_begin();
+	unsafe_put_user(err ? 0 : SIGCHLD, &infop->si_signo, Efault);
+	unsafe_put_user(0, &infop->si_errno, Efault);
+	unsafe_put_user((short)info.why, &infop->si_code, Efault);
+	unsafe_put_user(info.pid, &infop->si_pid, Efault);
+	unsafe_put_user(info.uid, &infop->si_uid, Efault);
+	unsafe_put_user(info.status, &infop->si_status, Efault);
+	user_access_end();
 	return err;
+Efault:
+	user_access_end();
+	return -EFAULT;
 }
 
 static long kernel_wait4(pid_t upid, int __user *stat_addr,
@@ -1736,13 +1739,20 @@ COMPAT_SYSCALL_DEFINE5(waitid,
 			return -EFAULT;
 	}
 
-	if (put_user(err ? 0 : SIGCHLD, &uinfo->si_signo) ||
-	    put_user(0, &uinfo->si_errno) ||
-	    put_user((short)info.why, &uinfo->si_code) ||
-	    put_user(info.pid, &uinfo->si_pid) ||
-	    put_user(info.uid, &uinfo->si_uid) ||
-	    put_user(info.status, &uinfo->si_status))
-		err = -EFAULT;
+	if (!uinfo)
+		return err;
+
+	user_access_begin();
+	unsafe_put_user(err ? 0 : SIGCHLD, &infop->si_signo, Efault);
+	unsafe_put_user(0, &infop->si_errno, Efault);
+	unsafe_put_user((short)info.why, &infop->si_code, Efault);
+	unsafe_put_user(info.pid, &infop->si_pid, Efault);
+	unsafe_put_user(info.uid, &infop->si_uid, Efault);
+	unsafe_put_user(info.status, &infop->si_status, Efault);
+	user_access_end();
 	return err;
+Efault:
+	user_access_end();
+	return -EFAULT;
 }
 #endif
-- 
2.11.0