From 5c4604e757ba9b193b09768d75a7d2105a5b883f Mon Sep 17 00:00:00 2001 From: Joonas Lahtinen 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 Suggested-by: Linus Torvalds Signed-off-by: Joonas Lahtinen Cc: # v4.0+ Cc: Akash Goel Cc: Chris Wilson Cc: Tvrtko Ursulin Cc: Adam Zabrocki Reviewed-by: Chris Wilson Reviewed-by: Tvrtko Ursulin #v1 Link: https://patchwork.freedesktop.org/patch/msgid/20190207085454.10598-1-joonas.lahtinen@linux.intel.com --- drivers/gpu/drm/i915/i915_gem.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 52b5a24be42b..2ea9b423de49 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1679,6 +1679,16 @@ 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. @@ -1737,7 +1747,7 @@ 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 -- 2.30.2