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Fri, 04 Apr 2025 01:27:42 -0700 (PDT) Date: Fri, 4 Apr 2025 11:27:39 +0300 From: Dan Carpenter To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: Rob Clark , Sumit Semwal , Gustavo Padovan , Dmitry Baryshkov , Pekka Paalanen , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH] dma-buf/sw_sync: Decrement refcount on error in sw_sync_ioctl_get_deadline() Message-ID: <03c838ab-3bc8-4e5a-9f0a-331254701b0c@stanley.mountain> References: <5dbd6105-3acf-47ad-84d6-2920171916ac@stanley.mountain> <0e832ed8-9692-43ba-869d-8db3b419f3a9@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0e832ed8-9692-43ba-869d-8db3b419f3a9@amd.com> On Mon, Mar 31, 2025 at 02:02:44PM +0200, Christian König wrote: > Am 31.03.25 um 11:45 schrieb Dan Carpenter: > > Call dma_fence_put(fence) before returning an error on this error path. > > > > Fixes: 70e67aaec2f4 ("dma-buf/sw_sync: Add fence deadline support") > > Signed-off-by: Dan Carpenter > > --- > > drivers/dma-buf/sw_sync.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c > > index f5905d67dedb..b7615c5c6cac 100644 > > --- a/drivers/dma-buf/sw_sync.c > > +++ b/drivers/dma-buf/sw_sync.c > > @@ -438,8 +438,10 @@ static int sw_sync_ioctl_get_deadline(struct sync_timeline *obj, unsigned long a > > return -EINVAL; > > > > pt = dma_fence_to_sync_pt(fence); > > - if (!pt) > > + if (!pt) { > > + dma_fence_put(fence); > > return -EINVAL; > > + } > > Good catch. > > I think it would be cleaner if we add an error label and then use "ret = -EINVAL; goto error;" here as well as a few lines below when ret is set to -ENOENT. > > This way we can also avoid the ret = 0 in the declaration and let the compiler actually check the lifetime of the assignment. > I had some issues with my email and it silently ate a bunch of outgoing email without saving a single trace of anything I had sent. I see this was one that was eaten. Unwind ladders don't work really well for things where you just take it for a little while and then drop it a few lines later. Such as here you take reference and then drop it or you take a lock and then drop it. Normally, you can add things to anywere in the unwind ladder but if you add an unlock to the ladder than you to add a weird bunny hop if the goto isn't holding the lock. It ends up getting confusing. With that kind of thing, I prefer to do the unlock before the goto. free_c: free(c); goto free_b; <-- bunny hop; unlock: unlock(); free_b: free(b); free_a: free(a); return ret; regards, dan carpenter diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c index f5905d67dedb..22a808995f10 100644 --- a/drivers/dma-buf/sw_sync.c +++ b/drivers/dma-buf/sw_sync.c @@ -438,15 +438,17 @@ static int sw_sync_ioctl_get_deadline(struct sync_timeline *obj, unsigned long a return -EINVAL; pt = dma_fence_to_sync_pt(fence); - if (!pt) - return -EINVAL; + if (!pt) { + ret = -EINVAL; + goto put_fence; + } spin_lock_irqsave(fence->lock, flags); - if (test_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags)) { - data.deadline_ns = ktime_to_ns(pt->deadline); - } else { + if (!test_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags)) { ret = -ENOENT; + goto unlock; } + data.deadline_ns = ktime_to_ns(pt->deadline); spin_unlock_irqrestore(fence->lock, flags); dma_fence_put(fence); @@ -458,6 +460,13 @@ static int sw_sync_ioctl_get_deadline(struct sync_timeline *obj, unsigned long a return -EFAULT; return 0; + +unlock: + spin_unlock_irqrestore(fence->lock, flags); +put_fence: + dma_fence_put(fence); + + return ret; } static long sw_sync_ioctl(struct file *file, unsigned int cmd,