commit 284e6d39516cc7f9fbceebb259849fcb41559a7b
author Richard Weinberger <richard@nod.at> Sun Jul 20 13:09:15 2014 +0200
committer Richard Weinberger <richard@nod.at> Sun Jul 20 13:09:15 2014 +0200
tree b921cdd0911583d68e3de7fb48a9ef67b0883bd6
parent ae5db6d12341684913a78b6537c0b9c22c999b5c

um: Ensure that a stub page cannot get unmapped

Trinity discovered an execution path such that a task
can unmap his stub page.

Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/kernel/tlb.c

diff --git a/arch/um/kernel/tlb.c b/arch/um/kernel/tlb.c
index 9472079..1fc619e 100644
--- a/arch/um/kernel/tlb.c
+++ b/arch/um/kernel/tlb.c
@@ -124,6 +124,9 @@
 	struct host_vm_op *last;
 	int ret = 0;
 
+	if ((addr >= STUB_START) && (addr < STUB_END))
+		return -EINVAL;
+
 	if (hvc->index != 0) {
 		last = &hvc->ops[hvc->index - 1];
 		if ((last->type == MUNMAP) &&