ipc: sysvsem: refuse clone(CLONE_SYSVSEM|CLONE_NEWIPC)

02fdb36a · Serge E. Hallyn <[email protected]> · 2008-04-29 01:01:00 -07:00

CLONE_NEWIPC|CLONE_SYSVSEM interaction isn't handled properly.  This can cause
a kernel memory corruption.  CLONE_NEWIPC must detach from the existing undo
lists.

Fix, part 3: refuse clone(CLONE_SYSVSEM|CLONE_NEWIPC).

With unshare, specifying CLONE_SYSVSEM means unshare the sysvsem.  So it seems
reasonable that CLONE_NEWIPC without CLONE_SYSVSEM would just imply
CLONE_SYSVSEM.

However with clone, specifying CLONE_SYSVSEM means *share* the sysvsem.  So
calling clone(CLONE_SYSVSEM|CLONE_NEWIPC) is explicitly asking for something
we can't allow.  So return -EINVAL in that case.

[[email protected]: cleanups]
Signed-off-by: Serge E. Hallyn <[email protected]>
Cc: Manfred Spraul <[email protected]>
Acked-by: "Eric W. Biederman" <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Pierre Peiffer <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: 02fdb36ae7f55db7757b623acd27a62d5000d755
Parents: 6013f67f

Changes

1 files changed · +12 −0

File	Status	Add	Del	Content
kernel/nsproxy.c	modified	+12	−0	View file

kernel/nsproxy.c

View file

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f5d332c..adc7851 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -139,6 +139,18 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 		goto out;
 	}
 
+	/*
+	 * 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) && (flags & CLONE_SYSVSEM)) {
+		err = -EINVAL;
+		goto out;
+	}
+
 	new_ns = create_new_namespaces(flags, tsk, tsk->fs);
 	if (IS_ERR(new_ns)) {
 		err = PTR_ERR(new_ns);