diff options
| author | David Hildenbrand <david@redhat.com> | 2023-01-02 17:08:56 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-01-18 17:12:57 -0800 |
| commit | 997931ce02b72f15c40e742ee035ce5643ba574f (patch) | |
| tree | 1e144b743cb0dcceabb92be8662b668372541ebf /drivers/misc/open-dice.c | |
| parent | b6b7a8faf05c709cd9f63d3b7d9c66bd91bc3b0d (diff) | |
| download | linux-997931ce02b72f15c40e742ee035ce5643ba574f.tar.gz | |
drivers/misc/open-dice: don't touch VM_MAYSHARE
A MAP_SHARED mapping always has VM_MAYSHARE set, and writable
(VM_MAYWRITE) MAP_SHARED mappings have VM_SHARED set as well. To identify
a MAP_SHARED mapping, it's sufficient to look at VM_MAYSHARE.
We cannot have VM_MAYSHARE|VM_WRITE mappings without having VM_SHARED set.
Consequently, current code will never actually end up clearing
VM_MAYSHARE and that code is confusing, because nobody is supposed to mess
with VM_MAYWRITE.
Let's clean it up and restructure the code. No functional change intended.
Link: https://lkml.kernel.org/r/20230102160856.500584-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nicolas Pitre <nico@fluxnic.net>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'drivers/misc/open-dice.c')
| -rw-r--r-- | drivers/misc/open-dice.c | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/drivers/misc/open-dice.c b/drivers/misc/open-dice.c index c61be3404c6f2..9dda47b3fd709 100644 --- a/drivers/misc/open-dice.c +++ b/drivers/misc/open-dice.c @@ -90,15 +90,13 @@ static int open_dice_mmap(struct file *filp, struct vm_area_struct *vma) { struct open_dice_drvdata *drvdata = to_open_dice_drvdata(filp); - /* Do not allow userspace to modify the underlying data. */ - if ((vma->vm_flags & VM_WRITE) && (vma->vm_flags & VM_SHARED)) - return -EPERM; - - /* Ensure userspace cannot acquire VM_WRITE + VM_SHARED later. */ - if (vma->vm_flags & VM_WRITE) - vma->vm_flags &= ~VM_MAYSHARE; - else if (vma->vm_flags & VM_SHARED) + if (vma->vm_flags & VM_MAYSHARE) { + /* Do not allow userspace to modify the underlying data. */ + if (vma->vm_flags & VM_WRITE) + return -EPERM; + /* Ensure userspace cannot acquire VM_WRITE later. */ vma->vm_flags &= ~VM_MAYWRITE; + } /* Create write-combine mapping so all clients observe a wipe. */ vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot); |