[PATCH -next] fork.c: Move check of clone NEWIPC and SYSVSEM to copy_process

From: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
To: unlisted-recipients:; (no To-header on input)
Cc: Marcos Paulo de Souza <marcos.souza.org@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>, Rik van Riel <riel@redhat.com>,
	Michal Hocko <mhocko@suse.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Hari Bathini <hbathini@linux.vnet.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH -next] fork.c: Move check of clone NEWIPC and SYSVSEM to copy_process
Date: Sun, 26 Nov 2017 14:06:52 -0200	[thread overview]
Message-ID: <20171126160717.14727-1-marcos.souza.org@gmail.com> (raw)

Currently this check for CLONE_NEWIPC with CLONE_SYSVSEM is done inside
copy_namespaces, resulting in a handful of error paths being executed if
these flags were used together. So, move this check to the beginning of
copy_process, exiting earlier if the condition is true.

This move is safe because copy_namespaces is called just from
copy_process function.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
---
 kernel/fork.c    | 11 +++++++++++
 kernel/nsproxy.c | 11 -----------
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 2113e252cb9d..691f9ba135fc 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1600,6 +1600,17 @@ static __latent_entropy struct task_struct *copy_process(
 		return ERR_PTR(-EINVAL);
 
 	/*
+	 * CLONE_NEWIPC must detach from the undolist: after switching
+	 * to a new ipc namespace, the semaphore arrays from the old
+	 * namespace are unreachable.  In clone parlance, CLONE_SYSVSEM
+	 * means share undolist with parent, so we must forbid using
+	 * it along with CLONE_NEWIPC.
+	 */
+	if ((clone_flags & (CLONE_NEWIPC | CLONE_SYSVSEM)) ==
+		(CLONE_NEWIPC | CLONE_SYSVSEM))
+		return ERR_PTR(-EINVAL);
+
+	/*
 	 * Thread groups must share signals as well, and detached threads
 	 * can only be started up within the thread group.
 	 */
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f6c5d330059a..30882727dff5 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -151,17 +151,6 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
 		return -EPERM;
 
-	/*
-	 * CLONE_NEWIPC must detach from the undolist: after switching
-	 * to a new ipc namespace, the semaphore arrays from the old
-	 * namespace are unreachable.  In clone parlance, CLONE_SYSVSEM
-	 * means share undolist with parent, so we must forbid using
-	 * it along with CLONE_NEWIPC.
-	 */
-	if ((flags & (CLONE_NEWIPC | CLONE_SYSVSEM)) ==
-		(CLONE_NEWIPC | CLONE_SYSVSEM)) 
-		return -EINVAL;
-
 	new_ns = create_new_namespaces(flags, tsk, user_ns, tsk->fs);
 	if (IS_ERR(new_ns))
 		return  PTR_ERR(new_ns);
-- 
2.13.6
