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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Tvrtko Ursulin <tvrtko.ursulin@intel.com>,
        Chris Wilson <chris@chris-wilson.co.uk>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>
Subject: [PATCH 4.19 189/205] drm/i915: Large page offsets for pread/pwrite
Date:   Mon, 19 Nov 2018 17:28:16 +0100
Message-Id: <20181119162641.847991372@linuxfoundation.org>
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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chris Wilson <chris@chris-wilson.co.uk>

commit ab0d6a141843e0b4b2709dfd37b53468b5452c3a upstream.

Handle integer overflow when computing the sub-page length for shmem
backed pread/pwrite.

Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181012140228.29783-1-chris@chris-wilson.co.uk
(cherry picked from commit a5e856a5348f6cd50889d125c40bbeec7328e466)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/i915/i915_gem.c |   12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1122,11 +1122,7 @@ i915_gem_shmem_pread(struct drm_i915_gem
 	offset = offset_in_page(args->offset);
 	for (idx = args->offset >> PAGE_SHIFT; remain; idx++) {
 		struct page *page = i915_gem_object_get_page(obj, idx);
-		int length;
-
-		length = remain;
-		if (offset + length > PAGE_SIZE)
-			length = PAGE_SIZE - offset;
+		unsigned int length = min_t(u64, remain, PAGE_SIZE - offset);
 
 		ret = shmem_pread(page, offset, length, user_data,
 				  page_to_phys(page) & obj_do_bit17_swizzling,
@@ -1570,11 +1566,7 @@ i915_gem_shmem_pwrite(struct drm_i915_ge
 	offset = offset_in_page(args->offset);
 	for (idx = args->offset >> PAGE_SHIFT; remain; idx++) {
 		struct page *page = i915_gem_object_get_page(obj, idx);
-		int length;
-
-		length = remain;
-		if (offset + length > PAGE_SIZE)
-			length = PAGE_SIZE - offset;
+		unsigned int length = min_t(u64, remain, PAGE_SIZE - offset);
 
 		ret = shmem_pwrite(page, offset, length, user_data,
 				   page_to_phys(page) & obj_do_bit17_swizzling,