Patch "staging: comedi: jr3_pci: fix possible null pointer dereference" has been added to the 4.4-stable tree

Patch "staging: comedi: jr3_pci: fix possible null pointer dereference" has been added to the 4.4-stable tree

[gregkh]

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

    staging: comedi: jr3_pci: fix possible null pointer dereference

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     staging-comedi-jr3_pci-fix-possible-null-pointer-dereference.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 45292be0b3db0b7f8286683b376e2d9f949d11f9 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Fri, 17 Feb 2017 11:09:08 +0000
Subject: staging: comedi: jr3_pci: fix possible null pointer dereference

From: Ian Abbott <abbotti@mev.co.uk>

commit 45292be0b3db0b7f8286683b376e2d9f949d11f9 upstream.

For some reason, the driver does not consider allocation of the
subdevice private data to be a fatal error when attaching the COMEDI
device.  It tests the subdevice private data pointer for validity at
certain points, but omits some crucial tests.  In particular,
`jr3_pci_auto_attach()` calls `jr3_pci_alloc_spriv()` to allocate and
initialize the subdevice private data, but the same function
subsequently dereferences the pointer to access the `next_time_min` and
`next_time_max` members without checking it first.  The other missing
test is in the timer expiry routine `jr3_pci_poll_dev()`, but it will
crash before it gets that far.

Fix the bug by returning `-ENOMEM` from `jr3_pci_auto_attach()` as soon
as one of the calls to `jr3_pci_alloc_spriv()` returns `NULL`.  The
COMEDI core will subsequently call `jr3_pci_detach()` to clean up.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/staging/comedi/drivers/jr3_pci.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/drivers/staging/comedi/drivers/jr3_pci.c
+++ b/drivers/staging/comedi/drivers/jr3_pci.c
@@ -726,11 +726,12 @@ static int jr3_pci_auto_attach(struct co
 		s->insn_read	= jr3_pci_ai_insn_read;
 
 		spriv = jr3_pci_alloc_spriv(dev, s);
-		if (spriv) {
-			/* Channel specific range and maxdata */
-			s->range_table_list	= spriv->range_table_list;
-			s->maxdata_list		= spriv->maxdata_list;
-		}
+		if (!spriv)
+			return -ENOMEM;
+
+		/* Channel specific range and maxdata */
+		s->range_table_list	= spriv->range_table_list;
+		s->maxdata_list		= spriv->maxdata_list;
 	}
 
 	/*  Reset DSP card */


Patches currently in stable-queue which might be from abbotti@mev.co.uk are

queue-4.4/staging-comedi-jr3_pci-fix-possible-null-pointer-dereference.patch
queue-4.4/staging-comedi-jr3_pci-cope-with-jiffies-wraparound.patch