We check whether the multiplies will overflow prior to calling
kmalloc_array so that we can respond with -EINVAL for the invalid user
arguments rather than treating it as an -ENOMEM that would otherwise
occur. However, as Dan Carpenter pointed out, we did an addition on the
unsigned int prior to passing to kmalloc_array where it would be
promoted to size_t for the calculation, thereby allowing it to overflow
and underallocate.
v2: buffer_count is currently limited to INT_MAX because we treat it as
signaled variable for LUT_HANDLE in eb_lookup_vma
v3: Move common checks for eb1/eb2 into the same function
v4: Put the check back for nfence*sizeof(user_fence) overflow
v5: access_ok uses ULONG_MAX but kvmalloc_array uses SIZE_MAX
v6: size_t and unsigned long are not type-equivalent on 32b
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 66 +++++++++++++++++++-----------
1 file changed, 43 insertions(+), 23 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 435ed95df144..53ccb27bfe91 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -2074,23 +2074,27 @@ static struct drm_syncobj **
get_fence_array(struct drm_i915_gem_execbuffer2 *args,
struct drm_file *file)
{
- const unsigned int nfences = args->num_cliprects;
+ const unsigned long nfences = args->num_cliprects;
struct drm_i915_gem_exec_fence __user *user;
struct drm_syncobj **fences;
- unsigned int n;
+ unsigned long n;
int err;
if (!(args->flags & I915_EXEC_FENCE_ARRAY))
return NULL;
- if (nfences > SIZE_MAX / sizeof(*fences))
+ /* Check multiplication overflow for access_ok() and kvmalloc_array() */
+ BUILD_BUG_ON(sizeof(size_t) > sizeof(unsigned long));
+ if (nfences > min_t(unsigned long,
+ ULONG_MAX / sizeof(*user),
+ SIZE_MAX / sizeof(*fences)))
return ERR_PTR(-EINVAL);
user = u64_to_user_ptr(args->cliprects_ptr);
- if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
+ if (!access_ok(VERIFY_READ, user, nfences * sizeof(*user)))
return ERR_PTR(-EFAULT);
- fences = kvmalloc_array(args->num_cliprects, sizeof(*fences),
+ fences = kvmalloc_array(nfences, sizeof(*fences),
__GFP_NOWARN | GFP_KERNEL);
if (!fences)
return ERR_PTR(-ENOMEM);
@@ -2447,6 +2451,26 @@ i915_gem_do_execbuffer(struct drm_device *dev,
return err;
}
+static size_t eb_element_size(void)
+{
+ return (sizeof(struct drm_i915_gem_exec_object2) +
+ sizeof(struct i915_vma *) +
+ sizeof(unsigned int));
+}
+
+static bool check_buffer_count(size_t count)
+{
+ const size_t sz = eb_element_size();
+
+ /*
+ * When using LUT_HANDLE, we impose a limit of INT_MAX for the lookup
+ * array size (see eb_create()). Otherwise, we can accept an array as
+ * large as can be addressed (though use large arrays at your peril)!
+ */
+
+ return !(count < 1 || count > INT_MAX || count > SIZE_MAX / sz - 1);
+}
+
/*
* Legacy execbuffer just creates an exec2 list from the original exec object
* list array and passes it to the real function.
@@ -2455,18 +2479,16 @@ int
i915_gem_execbuffer(struct drm_device *dev, void *data,
struct drm_file *file)
{
- const size_t sz = (sizeof(struct drm_i915_gem_exec_object2) +
- sizeof(struct i915_vma *) +
- sizeof(unsigned int));
struct drm_i915_gem_execbuffer *args = data;
struct drm_i915_gem_execbuffer2 exec2;
struct drm_i915_gem_exec_object *exec_list = NULL;
struct drm_i915_gem_exec_object2 *exec2_list = NULL;
+ const size_t count = args->buffer_count;
unsigned int i;
int err;
- if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
- DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
+ if (!check_buffer_count(count)) {
+ DRM_DEBUG("execbuf2 with %zd buffers\n", count);
return -EINVAL;
}
@@ -2485,9 +2507,9 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
return -EINVAL;
/* Copy in the exec list from userland */
- exec_list = kvmalloc_array(args->buffer_count, sizeof(*exec_list),
+ exec_list = kvmalloc_array(count, sizeof(*exec_list),
__GFP_NOWARN | GFP_KERNEL);
- exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
+ exec2_list = kvmalloc_array(count + 1, eb_element_size(),
__GFP_NOWARN | GFP_KERNEL);
if (exec_list == NULL || exec2_list == NULL) {
DRM_DEBUG("Failed to allocate exec list for %d buffers\n",
@@ -2498,7 +2520,7 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
}
err = copy_from_user(exec_list,
u64_to_user_ptr(args->buffers_ptr),
- sizeof(*exec_list) * args->buffer_count);
+ sizeof(*exec_list) * count);
if (err) {
DRM_DEBUG("copy %d exec entries failed %d\n",
args->buffer_count, err);
@@ -2548,16 +2570,14 @@ int
i915_gem_execbuffer2(struct drm_device *dev, void *data,
struct drm_file *file)
{
- const size_t sz = (sizeof(struct drm_i915_gem_exec_object2) +
- sizeof(struct i915_vma *) +
- sizeof(unsigned int));
struct drm_i915_gem_execbuffer2 *args = data;
struct drm_i915_gem_exec_object2 *exec2_list;
struct drm_syncobj **fences = NULL;
+ const size_t count = args->buffer_count;
int err;
- if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
- DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
+ if (!check_buffer_count(count)) {
+ DRM_DEBUG("execbuf2 with %zd buffers\n", count);
return -EINVAL;
}
@@ -2565,17 +2585,17 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
return -EINVAL;
/* Allocate an extra slot for use by the command parser */
- exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
+ exec2_list = kvmalloc_array(count + 1, eb_element_size(),
__GFP_NOWARN | GFP_KERNEL);
if (exec2_list == NULL) {
- DRM_DEBUG("Failed to allocate exec list for %d buffers\n",
- args->buffer_count);
+ DRM_DEBUG("Failed to allocate exec list for %zd buffers\n",
+ count);
return -ENOMEM;
}
if (copy_from_user(exec2_list,
u64_to_user_ptr(args->buffers_ptr),
- sizeof(*exec2_list) * args->buffer_count)) {
- DRM_DEBUG("copy %d exec entries failed\n", args->buffer_count);
+ sizeof(*exec2_list) * count)) {
+ DRM_DEBUG("copy %zd exec entries failed\n", count);
kvfree(exec2_list);
return -EFAULT;
}
