From: Tadeusz Struk tadeusz.struk@linaro.org
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" dvyukov@google.com Cc: stable stable@kernel.org Fixes: 6f23ee1fefdc ("USB: add binary API to usbmon") Suggested-by: PaX Team pageexec@freemail.hu # for the VM_MAYRITE portion Link: https://syzkaller.appspot.com/bug?id=2eb1f35d6525fa4a74d75b4244971e5b1411c95... Reported-by: syzbot+23f57c5ae902429285d7@syzkaller.appspotmail.com Signed-off-by: Tadeusz Struk tadeusz.struk@linaro.org Link: https://lore.kernel.org/r/20220919215957.205681-1-tadeusz.struk@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/mon/mon_bin.c | 5 +++++ 1 file changed, 5 insertions(+)
--- 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 *fil { /* 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);