[PATCH AUTOSEL 4.19 088/167] drm/i915: Sanity check mmap length against object size

[Sasha Levin]

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

[ Upstream commit 000c4f90e3f0194eef218ff2c6a8fd8ca1de4313 ]

We assumed that vm_mmap() would reject an attempt to mmap past the end of
the filp (our object), but we were wrong.

Applications that tried to use the mmap beyond the end of the object
would be greeted by a SIGBUS. After this patch, those applications will
be told about the error on creating the mmap, rather than at a random
moment on later access.

Reported-by: Antonio Argenziano <antonio.argenziano at intel.com>
Testcase: igt/gem_mmap/bad-size
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Antonio Argenziano <antonio.argenziano at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: stable at vger.kernel.org
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190314075829.16838-1-chris@chris-wilson.co.uk
(cherry picked from commit 794a11cb67201ad1bb61af510bb8460280feb3f3)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 drivers/gpu/drm/i915/i915_gem.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9634d3adb8d01..9372877100420 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1874,8 +1874,13 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
 	 * pages from.
 	 */
 	if (!obj->base.filp) {
-		i915_gem_object_put(obj);
-		return -ENXIO;
+		addr = -ENXIO;
+		goto err;
+	}
+
+	if (range_overflows(args->offset, args->size, (u64)obj->base.size)) {
+		addr = -EINVAL;
+		goto err;
 	}
 
 	addr = vm_mmap(obj->base.filp, 0, args->size,
@@ -1889,8 +1894,8 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
 		struct vm_area_struct *vma;
 
 		if (down_write_killable(&mm->mmap_sem)) {
-			i915_gem_object_put(obj);
-			return -EINTR;
+			addr = -EINTR;
+			goto err;
 		}
 		vma = find_vma(mm, addr);
 		if (vma && __vma_matches(vma, obj->base.filp, addr, args->size))
@@ -1908,12 +1913,10 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
 	i915_gem_object_put(obj);
 
 	args->addr_ptr = (uint64_t) addr;
-
 	return 0;
 
 err:
 	i915_gem_object_put(obj);
-
 	return addr;
 }
 
-- 
2.20.1