patch "USB: fix usbmon BUG trigger" added to usb-linus

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    USB: fix usbmon BUG trigger

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>From 46eb14a6e1585d99c1b9f58d0e7389082a5f466b Mon Sep 17 00:00:00 2001
From: Pete Zaitcev <zaitcev@redhat.com>
Date: Mon, 8 Jan 2018 15:46:41 -0600
Subject: USB: fix usbmon BUG trigger

Automated tests triggered this by opening usbmon and accessing the
mmap while simultaneously resizing the buffers. This bug was with
us since 2006, because typically applications only size the buffers
once and thus avoid racing. Reported by Kirill A. Shutemov.

Reported-by: <syzbot+f9831b881b3e849829fc@syzkaller.appspotmail.com>
Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/mon/mon_bin.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/mon/mon_bin.c b/drivers/usb/mon/mon_bin.c
index f6ae753ab99b..f932f40302df 100644
--- a/drivers/usb/mon/mon_bin.c
+++ b/drivers/usb/mon/mon_bin.c
@@ -1004,7 +1004,9 @@ static long mon_bin_ioctl(struct file *file, unsigned int cmd, unsigned long arg
 		break;
 
 	case MON_IOCQ_RING_SIZE:
+		mutex_lock(&rp->fetch_lock);
 		ret = rp->b_size;
+		mutex_unlock(&rp->fetch_lock);
 		break;
 
 	case MON_IOCT_RING_SIZE:
@@ -1231,12 +1233,16 @@ static int mon_bin_vma_fault(struct vm_fault *vmf)
 	unsigned long offset, chunk_idx;
 	struct page *pageptr;
 
+	mutex_lock(&rp->fetch_lock);
 	offset = vmf->pgoff << PAGE_SHIFT;
-	if (offset >= rp->b_size)
+	if (offset >= rp->b_size) {
+		mutex_unlock(&rp->fetch_lock);
 		return VM_FAULT_SIGBUS;
+	}
 	chunk_idx = offset / CHUNK_SIZE;
 	pageptr = rp->b_vec[chunk_idx].pg;
 	get_page(pageptr);
+	mutex_unlock(&rp->fetch_lock);
 	vmf->page = pageptr;
 	return 0;
 }
-- 
2.15.1