From b29f76fcf2db6615b416d98e28c7d81eff4c89a2 Mon Sep 17 00:00:00 2001 From: Tadeusz Struk Date: Mon, 19 Sep 2022 14:59:57 -0700 Subject: [PATCH] usb: mon: make mmapped memory read only commit a659daf63d16aa883be42f3f34ff84235c302198 upstream. Syzbot found an issue in usbmon module, where the user space client can corrupt the monitor's internal memory, causing the usbmon module to crash the kernel with segfault, UAF, etc. The reproducer mmaps the /dev/usbmon memory to user space, and overwrites it with arbitrary data, which causes all kinds of issues. Return an -EPERM error from mon_bin_mmap() if the flag VM_WRTIE is set. Also clear VM_MAYWRITE to make it impossible to change it to writable later. Cc: "Dmitry Vyukov" Cc: stable Fixes: 6f23ee1fefdc ("USB: add binary API to usbmon") Suggested-by: PaX Team # for the VM_MAYRITE portion Link: https://syzkaller.appspot.com/bug?id=2eb1f35d6525fa4a74d75b4244971e5b1411c95a Reported-by: syzbot+23f57c5ae902429285d7@syzkaller.appspotmail.com Signed-off-by: Tadeusz Struk Link: https://lore.kernel.org/r/20220919215957.205681-1-tadeusz.struk@linaro.org Signed-off-by: Greg Kroah-Hartman --- drivers/usb/mon/mon_bin.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/usb/mon/mon_bin.c b/drivers/usb/mon/mon_bin.c index 156aebf62e61..a6da9b72f46b 100644 --- a/drivers/usb/mon/mon_bin.c +++ b/drivers/usb/mon/mon_bin.c @@ -1267,6 +1267,11 @@ static int mon_bin_mmap(struct file *filp, struct vm_area_struct *vma) { /* don't do anything here: "fault" will set up page table entries */ vma->vm_ops = &mon_bin_vm_ops; + + if (vma->vm_flags & VM_WRITE) + return -EPERM; + + vma->vm_flags &= ~VM_MAYWRITE; vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP; vma->vm_private_data = filp->private_data; mon_bin_vma_open(vma); -- 2.20.1