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FAILED: patch "[PATCH] drm/i915: Prevent a race during I915_GEM_MMAP ioctl with WC" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Feb 18, 2019

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Stable branch DRM drivers Intel i915
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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 <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2e7bd10e05afb866b5fb13eda25095c35d7a27cc Mon Sep 17 00:00:00 2001
From: Joonas Lahtinen <[email protected]>
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 <[email protected]>
Suggested-by Linus Torvalds <[email protected]>
Signed-off-by Joonas Lahtinen <[email protected]>
Cc <[email protected]> # v4.0+
Cc Akash Goel <[email protected]>
Cc Chris Wilson <[email protected]>
Cc Tvrtko Ursulin <[email protected]>
Cc Adam Zabrocki <[email protected]>
Reviewed-by Chris Wilson <[email protected]>
Reviewed-by Tvrtko Ursulin <[email protected]> #v1
Link https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit 5c4604e757ba9b193b09768d75a7d2105a5b883f)
Signed-off-by Jani Nikula <[email protected]>
drivers/gpu/drm/i915/i915_gem.c +11 -1
index 216f52b744a6..c882ea94172c 100644
@@ -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