Patch "scsi: sg: protect against races between mmap() and SG_SET_RESERVED_SIZE" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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

    scsi: sg: protect against races between mmap() and SG_SET_RESERVED_SIZE

to the 4.9-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:
     scsi-sg-protect-against-races-between-mmap-and-sg_set_reserved_size.patch
and it can be found in the queue-4.9 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 6a8dadcca81fceff9976e8828cceb072873b7bd5 Mon Sep 17 00:00:00 2001
From: Todd Poynor <toddpoynor@google.com>
Date: Tue, 15 Aug 2017 22:41:08 -0700
Subject: scsi: sg: protect against races between mmap() and SG_SET_RESERVED_SIZE

From: Todd Poynor <toddpoynor@google.com>

commit 6a8dadcca81fceff9976e8828cceb072873b7bd5 upstream.

Take f_mutex around mmap() processing to protect against races with the
SG_SET_RESERVED_SIZE ioctl.  Ensure the reserve buffer length remains
consistent during the mapping operation, and set the "mmap called" flag
to prevent further changes to the reserved buffer size as an atomic
operation with the mapping.

[mkp: fixed whitespace]

Signed-off-by: Todd Poynor <toddpoynor@google.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/scsi/sg.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1244,6 +1244,7 @@ sg_mmap(struct file *filp, struct vm_are
 	unsigned long req_sz, len, sa;
 	Sg_scatter_hold *rsv_schp;
 	int k, length;
+	int ret = 0;
 
 	if ((!filp) || (!vma) || (!(sfp = (Sg_fd *) filp->private_data)))
 		return -ENXIO;
@@ -1254,8 +1255,11 @@ sg_mmap(struct file *filp, struct vm_are
 	if (vma->vm_pgoff)
 		return -EINVAL;	/* want no offset */
 	rsv_schp = &sfp->reserve;
-	if (req_sz > rsv_schp->bufflen)
-		return -ENOMEM;	/* cannot map more than reserved buffer */
+	mutex_lock(&sfp->f_mutex);
+	if (req_sz > rsv_schp->bufflen) {
+		ret = -ENOMEM;	/* cannot map more than reserved buffer */
+		goto out;
+	}
 
 	sa = vma->vm_start;
 	length = 1 << (PAGE_SHIFT + rsv_schp->page_order);
@@ -1269,7 +1273,9 @@ sg_mmap(struct file *filp, struct vm_are
 	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
 	vma->vm_private_data = sfp;
 	vma->vm_ops = &sg_mmap_vm_ops;
-	return 0;
+out:
+	mutex_unlock(&sfp->f_mutex);
+	return ret;
 }
 
 static void


Patches currently in stable-queue which might be from toddpoynor@google.com are

queue-4.9/scsi-sg-recheck-mmap_io-request-length-with-lock-held.patch
queue-4.9/scsi-sg-protect-against-races-between-mmap-and-sg_set_reserved_size.patch