usb: mon: make mmapped memory read only

stable inclusion
from stable-v5.10.148
commit 1b257f97fec43d7a8a4c9ada8538d14421861b0a
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5XTU4
CVE: CVE-2022-43750

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1b257f97fec43d7a8a4c9ada8538d14421861b0a

--------------------------------

commit a659daf6 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: 6f23ee1f ("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=2eb1f35d6525fa4a74d75b4244971e5b1411c95a
Reported-by: syzbot+23f57c5ae902429285d7@syzkaller.appspotmail.com
Signed-off-by: NTadeusz Struk <tadeusz.struk@linaro.org>
Link: https://lore.kernel.org/r/20220919215957.205681-1-tadeusz.struk@linaro.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZhao Wenhui <zhaowenhui8@huawei.com>
Reviewed-by: NZhang Qiao <zhangqiao22@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: NChen Hui <judy.chenhui@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/usb/mon/mon_bin.c

@@ -1268,6 +1268,11 @@ 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);