[3.19.y-ckt stable] Patch "cxl: Fix off by one error allowing subsequent mmap page to be accessed" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    cxl: Fix off by one error allowing subsequent mmap page to be accessed

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt5.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 8c980662880f58631a3a72d9d46f6f28ffff501e Mon Sep 17 00:00:00 2001
From: Ian Munsie <imunsie at au1.ibm.com>
Date: Tue, 7 Jul 2015 15:45:45 +1000
Subject: cxl: Fix off by one error allowing subsequent mmap page to be
 accessed

commit 10a5894f2dedd8a26b3132497445b314c0d952c4 upstream.

It was discovered that if a process mmaped their problem state area they
were able to access one page more than expected, potentially allowing
them to access the problem state area of an unrelated process.

This was due to a simple off by one error in the mmap fault handler
introduced in 0712dc7e73e59d79bcead5d5520acf4e9e917e87 ("cxl: Fix issues
when unmapping contexts"), which is fixed in this patch.

Fixes: 0712dc7e73e5 ("cxl: Fix issues when unmapping contexts")
Signed-off-by: Ian Munsie <imunsie at au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/misc/cxl/context.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/cxl/context.c b/drivers/misc/cxl/context.c
index d1b55fe..e4dc8cd 100644
--- a/drivers/misc/cxl/context.c
+++ b/drivers/misc/cxl/context.c
@@ -113,11 +113,11 @@ static int cxl_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)

 	if (ctx->afu->current_mode == CXL_MODE_DEDICATED) {
 		area = ctx->afu->psn_phys;
-		if (offset > ctx->afu->adapter->ps_size)
+		if (offset >= ctx->afu->adapter->ps_size)
 			return VM_FAULT_SIGBUS;
 	} else {
 		area = ctx->psn_phys;
-		if (offset > ctx->psn_size)
+		if (offset >= ctx->psn_size)
 			return VM_FAULT_SIGBUS;
 	}

--
1.9.1