On 10/11/23 10:03, Kees Cook wrote:
On Wed, Oct 11, 2023 at 08:03:43AM -0600, Gustavo A. R. Silva wrote:
Currently, a NULL pointer dereference will happen in function
`dma_fence_enable_sw_signaling()` (at line 615), in case `chain`
is not allocated in `mock_chain()` and this function returns
`NULL` (at line 86). See below:
drivers/dma-buf/st-dma-fence-chain.c:
86 chain = mock_chain(NULL, f, 1);
87 if (!chain)
88 err = -ENOMEM;
89
90 dma_fence_enable_sw_signaling(chain);
Instead of the larger patch, should line 88 here just do a "return
-ENOMEM" instead?
Nope. I would have to add a `goto` to skip `dma_fence_enable_sw_signaling(chain)`.
I originally thought of that, but as other _signaling() functions have
sanity-checks inside, I decided to go with that solution.
This bug has been there since Sep 2022. So, adding a sanity check inside that
function should prevent any other issue of this same kind to enter the codebase
and stay there for years.
--
Gustavo
-Kees
drivers/dma-buf/dma-fence.c:
611 void dma_fence_enable_sw_signaling(struct dma_fence *fence)
612 {
613 unsigned long flags;
614
615 spin_lock_irqsave(fence->lock, flags);
^^^^^^^^^^^
|
NULL pointer reference
if fence == NULL
616 __dma_fence_enable_signaling(fence);
617 spin_unlock_irqrestore(fence->lock, flags);
618 }
Fix this by adding a NULL check before dereferencing `fence` in
`dma_fence_enable_sw_signaling()`. This will prevent any other NULL
pointer dereference when the `fence` passed as an argument is `NULL`.
Addresses-Coverity: ("Dereference after null check")
Fixes: d62c43a953ce ("dma-buf: Enable signaling on fence for selftests")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
drivers/dma-buf/dma-fence.c | 9 ++++++++-
include/linux/dma-fence.h | 2 +-
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 8aa8f8cb7071..4d2f13560d0f 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -607,14 +607,21 @@ static bool __dma_fence_enable_signaling(struct dma_fence *fence)
* This will request for sw signaling to be enabled, to make the fence
* complete as soon as possible. This calls &dma_fence_ops.enable_signaling
* internally.
+ *
+ * Returns 0 on success and a negative error value when @fence is NULL.
*/
-void dma_fence_enable_sw_signaling(struct dma_fence *fence)
+int dma_fence_enable_sw_signaling(struct dma_fence *fence)
{
unsigned long flags;
+ if (!fence)
+ return -EINVAL;
+
spin_lock_irqsave(fence->lock, flags);
__dma_fence_enable_signaling(fence);
spin_unlock_irqrestore(fence->lock, flags);
+
+ return 0;
}
EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index ebe78bd3d121..1e4025e925e6 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -399,7 +399,7 @@ int dma_fence_add_callback(struct dma_fence *fence,
dma_fence_func_t func);
bool dma_fence_remove_callback(struct dma_fence *fence,
struct dma_fence_cb *cb);
-void dma_fence_enable_sw_signaling(struct dma_fence *fence);
+int dma_fence_enable_sw_signaling(struct dma_fence *fence);
/**
* dma_fence_is_signaled_locked - Return an indication if the fence
--
2.34.1
