Patch "s390/sclp_ctl: fix potential information leak with /dev/sclp" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    s390/sclp_ctl: fix potential information leak with /dev/sclp

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:
     s390-sclp_ctl-fix-potential-information-leak-with-dev-sclp.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 532c34b5fbf1687df63b3fcd5b2846312ac943c6 Mon Sep 17 00:00:00 2001
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Mon, 25 Apr 2016 17:54:28 +0200
Subject: s390/sclp_ctl: fix potential information leak with /dev/sclp

From: Martin Schwidefsky <schwidefsky@de.ibm.com>

commit 532c34b5fbf1687df63b3fcd5b2846312ac943c6 upstream.

The sclp_ctl_ioctl_sccb function uses two copy_from_user calls to
retrieve the sclp request from user space. The first copy_from_user
fetches the length of the request which is stored in the first two
bytes of the request. The second copy_from_user gets the complete
sclp request, but this copies the length field a second time.
A malicious user may have changed the length in the meantime.

Reported-by: Pengfei Wang <wpengfeinudt@gmail.com>
Reviewed-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Juerg Haefliger <juerg.haefliger@hpe.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/s390/char/sclp_ctl.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/s390/char/sclp_ctl.c
+++ b/drivers/s390/char/sclp_ctl.c
@@ -56,6 +56,7 @@ static int sclp_ctl_ioctl_sccb(void __us
 {
 	struct sclp_ctl_sccb ctl_sccb;
 	struct sccb_header *sccb;
+	unsigned long copied;
 	int rc;
 
 	if (copy_from_user(&ctl_sccb, user_area, sizeof(ctl_sccb)))
@@ -65,14 +66,15 @@ static int sclp_ctl_ioctl_sccb(void __us
 	sccb = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
 	if (!sccb)
 		return -ENOMEM;
-	if (copy_from_user(sccb, u64_to_uptr(ctl_sccb.sccb), sizeof(*sccb))) {
+	copied = PAGE_SIZE -
+		copy_from_user(sccb, u64_to_uptr(ctl_sccb.sccb), PAGE_SIZE);
+	if (offsetof(struct sccb_header, length) +
+	    sizeof(sccb->length) > copied || sccb->length > copied) {
 		rc = -EFAULT;
 		goto out_free;
 	}
-	if (sccb->length > PAGE_SIZE || sccb->length < 8)
-		return -EINVAL;
-	if (copy_from_user(sccb, u64_to_uptr(ctl_sccb.sccb), sccb->length)) {
-		rc = -EFAULT;
+	if (sccb->length < 8) {
+		rc = -EINVAL;
 		goto out_free;
 	}
 	rc = sclp_sync_request(ctl_sccb.cmdw, sccb);


Patches currently in stable-queue which might be from schwidefsky@de.ibm.com are

queue-4.4/0059-s390-cio-fix-measurement-characteristics-memleak.patch
queue-4.4/0061-s390-cio-update-measurement-characteristics.patch
queue-4.4/0094-s390-pci_dma-fix-DMA-table-corruption-with-4-TB-main.patch
queue-4.4/0103-s390-crypto-provide-correct-file-mode-at-device-regi.patch
queue-4.4/s390-sclp_ctl-fix-potential-information-leak-with-dev-sclp.patch
queue-4.4/0060-s390-cio-ensure-consistent-measurement-state.patch