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

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commit 6a8dadcca8 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>
This commit is contained in:
Todd Poynor
2017-08-15 22:41:08 -07:00
committed by Greg Kroah-Hartman
parent 9a4cabf3bf
commit 0d7592a03b
1 changed files with 9 additions and 3 deletions
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12
drivers/scsi/sg.c
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@@ -1254,6 +1254,7 @@ 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;
@@ -1264,8 +1265,11 @@ 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);
@@ -1279,7 +1283,9 @@ 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