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drm/i915: Avoid undefined behaviour of "u32 >> 32" 

When computing a hash for looking up relocation target handles in an
execbuf, we start with a large size for the hashtable and proceed to
halve it until the allocation succeeds. The final attempt is with an
order of 0 (i.e. a single element). This means that we then pass bits=0
to hash_32() which then computes "hash >> (32 - 0)" to lookup the single
element. Right shifting a value by the width of the operand is
undefined, so limit the smallest hash table we use to order 1.

v2: Keep the retry allocation flag for the final pass

Fixes: 4ff4b44cbb ("drm/i915: Store a direct lookup from object handle to vma")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170629150425.27508-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2017-06-29 16:04:25 +01:00
parent 886015a0ad
commit 4d470f7359
1 changed files with 24 additions and 14 deletions
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38
drivers/gpu/drm/i915/i915_gem_execbuffer.c
View File

@ -288,20 +288,26 @@ static int eb_create(struct i915_execbuffer *eb)
* direct lookup.
*/
do {
unsigned int flags;
/* While we can still reduce the allocation size, don't
* raise a warning and allow the allocation to fail.
* On the last pass though, we want to try as hard
* as possible to perform the allocation and warn
* if it fails.
*/
flags = GFP_TEMPORARY;
if (size > 1)
flags |= __GFP_NORETRY | __GFP_NOWARN;
eb->buckets = kzalloc(sizeof(struct hlist_head) << size,
GFP_TEMPORARY |
__GFP_NORETRY |
__GFP_NOWARN);
flags);
if (eb->buckets)
break;
} while (--size);
if (unlikely(!eb->buckets)) {
eb->buckets = kzalloc(sizeof(struct hlist_head),
GFP_TEMPORARY);
if (unlikely(!eb->buckets))
return -ENOMEM;
}
if (unlikely(!size))
return -ENOMEM;
eb->lut_size = size;
} else {
@ -452,7 +458,7 @@ eb_add_vma(struct i915_execbuffer *eb,
return err;
}
if (eb->lut_size >= 0) {
if (eb->lut_size > 0) {
vma->exec_handle = entry->handle;
hlist_add_head(&vma->exec_node,
&eb->buckets[hash_32(entry->handle,
@ -895,7 +901,7 @@ static void eb_release_vmas(const struct i915_execbuffer *eb)
static void eb_reset_vmas(const struct i915_execbuffer *eb)
{
eb_release_vmas(eb);
if (eb->lut_size >= 0)
if (eb->lut_size > 0)
memset(eb->buckets, 0,
sizeof(struct hlist_head) << eb->lut_size);
}
@ -904,7 +910,7 @@ static void eb_destroy(const struct i915_execbuffer *eb)
{
GEM_BUG_ON(eb->reloc_cache.rq);
if (eb->lut_size >= 0)
if (eb->lut_size > 0)
kfree(eb->buckets);
}
@ -2180,8 +2186,11 @@ i915_gem_do_execbuffer(struct drm_device *dev,
}
}
if (eb_create(&eb))
return -ENOMEM;
err = eb_create(&eb);
if (err)
goto err_out_fence;
GEM_BUG_ON(!eb.lut_size);
err = eb_select_context(&eb);
if (unlikely(err))
@ -2341,6 +2350,7 @@ err_rpm:
i915_gem_context_put(eb.ctx);
err_destroy:
eb_destroy(&eb);
err_out_fence:
if (out_fence_fd != -1)
put_unused_fd(out_fence_fd);
err_in_fence: