2017-08-16 05:41:29

by Todd Poynor

Subject: [PATCH] sg: protect against races between mmap() and SG_SET_RESERVED_SIZE

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.

Signed-off-by: Todd Poynor <[email protected]>
---
drivers/scsi/sg.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 3a44b4bc872b..a20718e9f1f4 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1233,6 +1233,7 @@ 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;
@@ -1243,8 +1244,11 @@ 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);
@@ -1258,7 +1262,9 @@ 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
--
2.14.1.480.gb18f417b89-goog

2017-08-23 01:48:57

by Douglas Gilbert

Subject: Re: [PATCH] sg: protect against races between mmap() and SG_SET_RESERVED_SIZE

On 2017-08-16 01:41 AM, Todd Poynor wrote:
> 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.
>
> Signed-off-by: Todd Poynor <[email protected]>
Acked-by: Douglas Gilbert <[email protected]>

Thanks.

> ---
> drivers/scsi/sg.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index 3a44b4bc872b..a20718e9f1f4 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -1233,6 +1233,7 @@ 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;
> @@ -1243,8 +1244,11 @@ 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);
> @@ -1258,7 +1262,9 @@ 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
>

2017-08-23 02:21:19

by Martin K. Petersen

Subject: Re: [PATCH] sg: protect against races between mmap() and SG_SET_RESERVED_SIZE

Todd,

> 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.

Applied to 4.14/scsi-queue (with a slight whitespace fix). Thanks!

--
Martin K. Petersen Oracle Linux Engineering