linux-kernel - [PATCH v4 06/11] coredump: validate socket name as it is written

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Message-Id: <20250507-work-coredump-socket-v4-6-af0ef317b2d0@kernel.org>
Date: Wed, 07 May 2025 18:13:39 +0200
From: Christian Brauner <brauner@...nel.org>
To: Kuniyuki Iwashima <kuniyu@...zon.com>, linux-fsdevel@...r.kernel.org, 
 Jann Horn <jannh@...gle.com>
Cc: Eric Dumazet <edumazet@...gle.com>, Oleg Nesterov <oleg@...hat.com>, 
 "David S. Miller" <davem@...emloft.net>, 
 Alexander Viro <viro@...iv.linux.org.uk>, 
 Daan De Meyer <daan.j.demeyer@...il.com>, 
 David Rheinsberg <david@...dahead.eu>, Jakub Kicinski <kuba@...nel.org>, 
 Jan Kara <jack@...e.cz>, Lennart Poettering <lennart@...ttering.net>, 
 Luca Boccassi <bluca@...ian.org>, Mike Yuan <me@...dnzj.com>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, 
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
 Christian Brauner <brauner@...nel.org>, 
 Alexander Mikhalitsyn <alexander@...alicyn.com>
Subject: [PATCH v4 06/11] coredump: validate socket name as it is written

In contrast to other parameters written into
/proc/sys/kernel/core_pattern that never fail we can validate enabling
the new AF_UNIX support. This is obviously racy as hell but it's always
been that way.

Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 fs/coredump.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index d61e15d855d2..0f00f77be988 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -1200,10 +1200,21 @@ void validate_coredump_safety(void)
 static int proc_dostring_coredump(const struct ctl_table *table, int write,
 		  void *buffer, size_t *lenp, loff_t *ppos)
 {
-	int error = proc_dostring(table, write, buffer, lenp, ppos);
+	int error;
+	ssize_t retval;
+	char old_core_pattern[CORENAME_MAX_SIZE];

-	if (!error)
-		validate_coredump_safety();
+	retval = strscpy(old_core_pattern, core_pattern, CORENAME_MAX_SIZE);
+
+	error = proc_dostring(table, write, buffer, lenp, ppos);
+	if (error)
+		return error;
+	if (core_pattern[0] == '@' && strcmp(core_pattern, "@linuxafsk/coredump.socket")) {
+		strscpy(core_pattern, old_core_pattern, retval + 1);
+		return -EINVAL;
+	}
+
+	validate_coredump_safety();
 	return error;
 }

-- 
2.47.2