patch "xhci: Don't add a virt_dev to the devs array before it's fully" added to usb-linus

[<gregkh@linuxfoundation.org>]

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

    xhci: Don't add a virt_dev to the devs array before it's fully

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 5d9b70f7d52eb14bb37861c663bae44de9521c35 Mon Sep 17 00:00:00 2001
From: Mathias Nyman <mathias.nyman@linux.intel.com>
Date: Fri, 8 Dec 2017 18:10:05 +0200
Subject: xhci: Don't add a virt_dev to the devs array before it's fully
 allocated

Avoid null pointer dereference if some function is walking through the
devs array accessing members of a new virt_dev that is mid allocation.

Add the virt_dev to xhci->devs[i] _after_ the virt_device and all its
members are properly allocated.

issue found by KASAN: null-ptr-deref in xhci_find_slot_id_by_port

"Quick analysis suggests that xhci_alloc_virt_device() is not mutex
protected. If so, there is a time frame where xhci->devs[slot_id] is set
but not fully initialized. Specifically, xhci->devs[i]->udev can be NULL."

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/host/xhci-mem.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 15f7d422885f..3a29b32a3bd0 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -971,10 +971,9 @@ int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
 		return 0;
 	}
 
-	xhci->devs[slot_id] = kzalloc(sizeof(*xhci->devs[slot_id]), flags);
-	if (!xhci->devs[slot_id])
+	dev = kzalloc(sizeof(*dev), flags);
+	if (!dev)
 		return 0;
-	dev = xhci->devs[slot_id];
 
 	/* Allocate the (output) device context that will be used in the HC. */
 	dev->out_ctx = xhci_alloc_container_ctx(xhci, XHCI_CTX_TYPE_DEVICE, flags);
@@ -1015,9 +1014,17 @@ int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
 
 	trace_xhci_alloc_virt_device(dev);
 
+	xhci->devs[slot_id] = dev;
+
 	return 1;
 fail:
-	xhci_free_virt_device(xhci, slot_id);
+
+	if (dev->in_ctx)
+		xhci_free_container_ctx(xhci, dev->in_ctx);
+	if (dev->out_ctx)
+		xhci_free_container_ctx(xhci, dev->out_ctx);
+	kfree(dev);
+
 	return 0;
 }
 
-- 
2.15.1