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    Subject[PATCH 4.13 43/47] scsi: sg: protect against races between mmap() and SG_SET_RESERVED_SIZE
    Date
    4.13-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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
    @@ -1233,6 +1233,7 @@ 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;
    @@ -1243,8 +1244,11 @@ 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);
    @@ -1258,7 +1262,9 @@ 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

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