From 4cb19355ea19995941ccaad115dbfac6b75215ca Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Wed, 16 Nov 2016 09:00:38 -0800 Subject: device-dax: fail all private mapping attempts The device-dax implementation originally tried to be tricky and allow private read-only mappings, but in the process allowed writable MAP_PRIVATE + MAP_NORESERVE mappings. For simplicity and predictability just fail all private mapping attempts since device-dax memory is statically allocated and will never support overcommit. Cc: Cc: Dave Hansen Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap") Reported-by: Pawel Lebioda Signed-off-by: Dan Williams --- drivers/dax/dax.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/dax/dax.c') diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c index 0e499bfca41c..3d94ff20fdca 100644 --- a/drivers/dax/dax.c +++ b/drivers/dax/dax.c @@ -270,8 +270,8 @@ static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma, if (!dax_dev->alive) return -ENXIO; - /* prevent private / writable mappings from being established */ - if ((vma->vm_flags & (VM_NORESERVE|VM_SHARED|VM_WRITE)) == VM_WRITE) { + /* prevent private mappings from being established */ + if ((vma->vm_flags & VM_SHARED) != VM_SHARED) { dev_info(dev, "%s: %s: fail, attempted private mapping\n", current->comm, func); return -EINVAL; -- cgit v1.2.3-70-g09d2 From 325896ffdf90f7cbd59fb873b7ba20d60d1ddf3c Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Tue, 6 Dec 2016 17:03:35 -0800 Subject: device-dax: fix private mapping restriction, permit read-only Hugh notes in response to commit 4cb19355ea19 "device-dax: fail all private mapping attempts": "I think that is more restrictive than you intended: haven't tried, but I believe it rejects a PROT_READ, MAP_SHARED, O_RDONLY fd mmap, leaving no way to mmap /dev/dax without write permission to it." Indeed it does restrict read-only mappings, switch to checking VM_MAYSHARE, not VM_SHARED. Cc: Cc: Dave Hansen Cc: Pawel Lebioda Fixes: 4cb19355ea19 ("device-dax: fail all private mapping attempts") Reported-by: Hugh Dickins Signed-off-by: Dan Williams --- drivers/dax/dax.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/dax/dax.c') diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c index 3d94ff20fdca..286447a83dab 100644 --- a/drivers/dax/dax.c +++ b/drivers/dax/dax.c @@ -271,7 +271,7 @@ static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma, return -ENXIO; /* prevent private mappings from being established */ - if ((vma->vm_flags & VM_SHARED) != VM_SHARED) { + if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) { dev_info(dev, "%s: %s: fail, attempted private mapping\n", current->comm, func); return -EINVAL; -- cgit v1.2.3-70-g09d2