Am 25.10.24 um 08:52 schrieb Friedrich Vock:
On 24.10.24 22:29, Matthew Brost wrote:
On Thu, Oct 24, 2024 at 02:41:57PM +0200, Christian König wrote:
Reports indicates that some userspace applications try to merge more
than
80k of fences into a single dma_fence_array leading to a warning from
Really, yikes.
Not really IME. Unless Christian means some reports I don't have access
to, the cases where userspace applications tried to do that were really
just cases where the fence count exploded exponentially because
dma_fence_unwrap_merge failed to actually merge identical fences (see
patch 2). At no point have I actually seen apps trying to merge 80k+
unique fences.
While working on it I've modified our stress test tool to send the same
1GiB SDMA copy to 100k different contexts.
Turned out it's perfectly possible to create so many fences, there is
nothing blocking userspace to do it.
While this isn't a realistic use case the kernel should at least not
crash or spill a warning, but either handle or reject it gracefully.
Friedrich can you confirm that patch two in this series fixes the
problem? I would really like to get it into drm-misc-fixes before 6.12
comes out.
Thanks,
Christian.
Regards,
Friedrich
kzalloc() that the requested size becomes to big.
While that is clearly an userspace bug we should probably handle
that case
gracefully in the kernel.
So we can either reject requests to merge more than a reasonable
amount of
fences (64k maybe?) or we can start to use kvzalloc() instead of
kzalloc().
This patch here does the later.
This patch seems reasonable to me if the above use is in fact valid.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
CC: stable@xxxxxxxxxxxxxxx
Fixes tag?
Patch itself LGTM:
Reviewed-by: Matthew Brost <matthew.brost@xxxxxxxxx>
---
drivers/dma-buf/dma-fence-array.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/dma-buf/dma-fence-array.c
b/drivers/dma-buf/dma-fence-array.c
index 8a08ffde31e7..46ac42bcfac0 100644
--- a/drivers/dma-buf/dma-fence-array.c
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -119,8 +119,8 @@ static void dma_fence_array_release(struct
dma_fence *fence)
for (i = 0; i < array->num_fences; ++i)
dma_fence_put(array->fences[i]);
- kfree(array->fences);
- dma_fence_free(fence);
+ kvfree(array->fences);
+ kvfree_rcu(fence, rcu);
}
static void dma_fence_array_set_deadline(struct dma_fence *fence,
@@ -153,7 +153,7 @@ struct dma_fence_array
*dma_fence_array_alloc(int num_fences)
{
struct dma_fence_array *array;
- return kzalloc(struct_size(array, callbacks, num_fences),
GFP_KERNEL);
+ return kvzalloc(struct_size(array, callbacks, num_fences),
GFP_KERNEL);
}
EXPORT_SYMBOL(dma_fence_array_alloc);
--
2.34.1
