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Commit 57923c95 authored by Todd Poynor's avatar Todd Poynor Committed by Greg Kroah-Hartman
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scsi: sg: protect against races between mmap() and SG_SET_RESERVED_SIZE 



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: default avatarTodd Poynor <toddpoynor@google.com>
Acked-by: default avatarDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 61b491f5

drivers/scsi/sg.c

+9 −3
Original line number Diff line number Diff line
@@ -1295,6 +1295,7 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma) 
	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;
@@ -1305,8 +1306,11 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma) 
	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);
@@ -1320,7 +1324,9 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma) 
	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