From 6fe9d02cb75c381b65b83f40c90ebc8d5870639a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <ckoenig.leichtzumerken@gmail.com>
Date: Wed, 10 Aug 2022 19:26:17 +0200
Subject: dma-buf/dma-resv: check if the new fence is really later
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Git-commit: a3f7c10a269d5b77dd5822ade822643ced3057f0
Patch-mainline: v6.0-rc4
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225 jsc#PED-2849
Previously when we added a fence to a dma_resv object we always
assumed the the newer than all the existing fences.
With Jason's work to add an UAPI to explicit export/import that's not
necessary the case any more. So without this check we would allow
userspace to force the kernel into an use after free error.
Since the change is very small and defensive it's probably a good
idea to backport this to stable kernels as well just in case others
are using the dma_resv object in the same way.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220810172617.140047-1-christian.koenig@amd.com
Cc: stable@vger.kernel.org # v5.19+
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/dma-buf/dma-resv.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 205acb2c744d..e3885c90a3ac 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -295,7 +295,8 @@ void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
enum dma_resv_usage old_usage;
dma_resv_list_entry(fobj, i, obj, &old, &old_usage);
- if ((old->context == fence->context && old_usage >= usage) ||
+ if ((old->context == fence->context && old_usage >= usage &&
+ dma_fence_is_later(fence, old)) ||
dma_fence_is_signaled(old)) {
dma_resv_list_set(fobj, i, fence, usage);
dma_fence_put(old);
--
2.38.1