4.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Richard Weinberger <rich...@nod.at>
commit 56b88a3bf97a39d3f4f010509917b76a865a6dc8 upstream.
We have to exclude memory locations <= PAGE_SIZE from
the condition and let the kernel mode fault path catch it.
Otherwise a kernel NULL pointer exception will be reported
as a kernel user space access.
Fixes: d2313084e2c (um: Catch unprotected user memory access)
Signed-off-by: Richard Weinberger <rich...@nod.at>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/um/kernel/trap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -220,7 +220,7 @@ unsigned long segv(struct faultinfo fi,
show_regs(container_of(regs, struct pt_regs, regs));
panic("Segfault with no mm");
}
- else if (!is_user && address < TASK_SIZE) {
+ else if (!is_user && address > PAGE_SIZE && address < TASK_SIZE) {
show_regs(container_of(regs, struct pt_regs, regs));
panic("Kernel tried to access user memory at addr 0x%lx, ip
0x%lx",
address, ip);
--
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