linux-kernel - [PATCH v5 3/4] scm: Convert put

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Message-ID: <793219313f641eda09a892d06768d2837246bf9f.1763396724.git.christophe.leroy@csgroup.eu>
Date: Mon, 17 Nov 2025 17:43:43 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>,
	Ingo Molnar <mingo@...hat.com>,
	Darren Hart <dvhart@...radead.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	"Andre Almeida" <andrealmeid@...lia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Kuniyuki Iwashima <kuniyu@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Willem de Bruijn <willemb@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	Simon Horman <horms@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nichlas Piggin <npiggin@...il.com>,
	linux-block@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v5 3/4] scm: Convert put_cmsg() to scoped user access

Replace the open coded implementation with the scoped user access
guards.

No functional change intended.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
v5: New
---
 net/core/scm.c | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/net/core/scm.c b/net/core/scm.c
index 66eaee783e8b..cd87f66671aa 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -273,17 +273,13 @@ int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
 
 		check_object_size(data, cmlen - sizeof(*cm), true);
 
-		if (can_do_masked_user_access())
-			cm = masked_user_access_begin(cm);
-		else if (!user_write_access_begin(cm, cmlen))
-			goto efault;
-
-		unsafe_put_user(cmlen, &cm->cmsg_len, efault_end);
-		unsafe_put_user(level, &cm->cmsg_level, efault_end);
-		unsafe_put_user(type, &cm->cmsg_type, efault_end);
-		unsafe_copy_to_user(CMSG_USER_DATA(cm), data,
-				    cmlen - sizeof(*cm), efault_end);
-		user_write_access_end();
+		scoped_user_write_access_size(cm, cmlen, efault) {
+			unsafe_put_user(cmlen, &cm->cmsg_len, efault);
+			unsafe_put_user(level, &cm->cmsg_level, efault);
+			unsafe_put_user(type, &cm->cmsg_type, efault);
+			unsafe_copy_to_user(CMSG_USER_DATA(cm), data,
+					    cmlen - sizeof(*cm), efault);
+		}
 	} else {
 		struct cmsghdr *cm = msg->msg_control;
 
@@ -301,8 +297,6 @@ int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
 	msg->msg_controllen -= cmlen;
 	return 0;
 
-efault_end:
-	user_write_access_end();
 efault:
 	return -EFAULT;
 }
-- 
2.49.0