The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 2e7bd10e05afb866b5fb13eda25095c35d7a27cc Mon Sep 17 00:00:00 2001
From: Joonas Lahtinen joonas.lahtinen@linux.intel.com Date: Thu, 7 Feb 2019 10:54:53 +0200 Subject: [PATCH] drm/i915: Prevent a race during I915_GEM_MMAP ioctl with WC set
Make sure the underlying VMA in the process address space is the same as it was during vm_mmap to avoid applying WC to wrong VMA.
A more long-term solution would be to have vm_mmap_locked variant in linux/mmap.h for when caller wants to hold mmap_sem for an extended duration.
v2: - Refactor the compare function
Fixes: 1816f9236303 ("drm/i915: Support creation of unbound wc user mappings for objects") Reported-by: Adam Zabrocki adamza@microsoft.com Suggested-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Joonas Lahtinen joonas.lahtinen@linux.intel.com Cc: stable@vger.kernel.org # v4.0+ Cc: Akash Goel akash.goel@intel.com Cc: Chris Wilson chris@chris-wilson.co.uk Cc: Tvrtko Ursulin tvrtko.ursulin@linux.intel.com Cc: Adam Zabrocki adamza@microsoft.com Reviewed-by: Chris Wilson chris@chris-wilson.co.uk Reviewed-by: Tvrtko Ursulin tvrtko.ursulin@intel.com #v1 Link: https://patchwork.freedesktop.org/patch/msgid/20190207085454.10598-1-joonas.... (cherry picked from commit 5c4604e757ba9b193b09768d75a7d2105a5b883f) Signed-off-by: Jani Nikula jani.nikula@intel.com
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 216f52b744a6..c882ea94172c 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1824,6 +1824,16 @@ i915_gem_sw_finish_ioctl(struct drm_device *dev, void *data, return 0; }
+static inline bool +__vma_matches(struct vm_area_struct *vma, struct file *filp, + unsigned long addr, unsigned long size) +{ + if (vma->vm_file != filp) + return false; + + return vma->vm_start == addr && (vma->vm_end - vma->vm_start) == size; +} + /** * i915_gem_mmap_ioctl - Maps the contents of an object, returning the address * it is mapped to. @@ -1882,7 +1892,7 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data, return -EINTR; } vma = find_vma(mm, addr); - if (vma) + if (vma && __vma_matches(vma, obj->base.filp, addr, args->size)) vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags)); else