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: [PATCH] scsi: 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.
[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>
---
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 bda438e1fb1d..f5705a95319f 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1262,6 +1262,7 @@ 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;
@@ -1272,8 +1273,11 @@ 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);
@@ -1287,7 +1291,9 @@ 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
--
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