From 6a8dadcca81fceff9976e8828cceb072873b7bd5 Mon Sep 17 00:00:00 2001 From: Todd Poynor 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 Acked-by: Douglas Gilbert Signed-off-by: Martin K. Petersen --- 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 -- 2.11.0