From 000c4f90e3f0194eef218ff2c6a8fd8ca1de4313 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 14 Mar 2019 07:58:29 +0000
Subject: [PATCH] drm/i915: Sanity check mmap length against object size
Git-commit: 000c4f90e3f0194eef218ff2c6a8fd8ca1de4313
Patch-mainline: v5.1-rc2
No-fix: 794a11cb67201ad1bb61af510bb8460280feb3f3
References: bsc#1111666

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@intel.com>
Testcase: igt/gem_mmap/bad-size
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Antonio Argenziano <antonio.argenziano@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@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@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_gem.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1882,8 +1882,13 @@ i915_gem_mmap_ioctl(struct drm_device *d
 	 * 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,
@@ -1897,8 +1902,8 @@ i915_gem_mmap_ioctl(struct drm_device *d
 		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))
@@ -1916,12 +1921,10 @@ i915_gem_mmap_ioctl(struct drm_device *d
 	i915_gem_object_put(obj);
 
 	args->addr_ptr = (uint64_t) addr;
-
 	return 0;
 
 err:
 	i915_gem_object_put(obj);
-
 	return addr;
 }