tree 2d4d320606408356b5bfb4f54ac5ab278545c404
parent d2f96e17ca75f183cfd50ff0b6655fb74e502a1e
author Jann Horn <jannh@google.com> 1529944450 +0200
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1536516084 +0200

sys: don't hold uts_sem while accessing userspace memory

commit 42a0cc3478584d4d63f68f2f5af021ddbea771fa upstream.

Holding uts_sem as a writer while accessing userspace memory allows a
namespace admin to stall all processes that attempt to take uts_sem.
Instead, move data through stack buffers and don't access userspace memory
while uts_sem is held.

Cc: stable@vger.kernel.org
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>