From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6533246AF0B for ; Fri, 15 May 2026 11:46:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778845574; cv=none; b=CkqtBPvo75LnDAvbUZuOjh8d/4V8ZcoU4v4jbKELTHoamrakuBbQVUV2+u/21/4o+Hg5By8M0j9pkRZRokMLRjz/ugYdr4KWIh3l6Imhis+jZ+rYLkaz2IBIjp9F+kcyirS80I6c3YpXJEgO1NMX907U2bIV/rNSnh5QMquSpqA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778845574; c=relaxed/simple; bh=u3OXNV1ZsGJ7YV+75tbKsC2Qixqc1UjjuVP+PF3T+n8=; h=Subject:To:From:Date:Message-ID:MIME-Version:Content-Type; b=krG7cFZsKZd7wnrwSNAI1qMUFsxfH8XNTIHpF/ijSH6dq1G8Q0CQOtLm0ebguVRiShaE82LAyFe6k64ozDCdlrqbdTaQ3AQGH7IWBOw64oVs/x/KWsOUDMnU19a3bgPPB+FZYlmUHEwbgowjHElwwCHw/F2hwmtWo62QT3OJPDc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=hx1YB6Ii; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="hx1YB6Ii" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BD3FEC2BCB0; Fri, 15 May 2026 11:46:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778845574; bh=u3OXNV1ZsGJ7YV+75tbKsC2Qixqc1UjjuVP+PF3T+n8=; h=Subject:To:From:Date:From; b=hx1YB6IiiVRhIp3W5wulLx/7V8N11LpcYJjLHzYKysJnEuU1Qcb7CM7sYlbL/aK60 Pz4OHIvWLEF2zNxAGfQPL91zWNujE8Jvraqfb55UOtb1ViZIfo9CATShyxtSuZ1THc WHmcn/KkP40uP5DH4Zh9OQ2UCtTv7sxh/EHLrsq4= Subject: patch "iio: buffer: Fix DMA fence leak in iio_buffer_enqueue_dmabuf()" added to char-misc-linus To: benoit.monin@bootlin.com,Stable@vger.kernel.org,jamesnuss@nanometrics.ca,jic23@kernel.org,paul@crapouillou.net From: Date: Fri, 15 May 2026 13:45:56 +0200 Message-ID: <2026051556-overrate-renegade-4eae@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is a note to let you know that I've just added the patch titled iio: buffer: Fix DMA fence leak in iio_buffer_enqueue_dmabuf() to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-linus branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will hopefully also be merged in Linus's tree for the next -rc kernel release. If you have any questions about this process, please let me know. >From a093999355084bdbfe6e97f1dd232e58a1525f0b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Beno=C3=AEt=20Monin?= Date: Wed, 1 Apr 2026 17:24:58 +0200 Subject: iio: buffer: Fix DMA fence leak in iio_buffer_enqueue_dmabuf() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit iio_buffer_enqueue_dmabuf() allocates a struct iio_dma_fence (104 bytes, kmalloc-128) via kmalloc_obj()+dma_fence_init(), which sets the initial kref to 1. It then calls dma_resv_add_fence() which takes a second reference (kref=2), and stores a raw pointer in block->fence. On the success path the function returns without calling dma_fence_put() to release the initial reference, so every buffer enqueue permanently leaks one kmalloc-128 allocation. The iio_buffer_cleanup() work item only releases the temporary reference taken during completion signalling by iio_buffer_signal_dmabuf_done(); the initial reference from dma_fence_init() is never released. With four iio_rwdev instances at 240kHz and 512 samples per buffer, this produces ~1875 kmalloc-128 allocations per second matching the observed slab growth exactly. A test with ftrace confirmed that the dma_fence_destroy event was never triggered. Fix by calling dma_fence_put() after dma_resv_add_fence(), transferring ownership of the fence to the DMA reservation object. The DMA fence then gets properly discarded after being signalled. Fixes: 3e26d9f08fbe0 ("iio: core: Add new DMABUF interface infrastructure") Originally-by: James Nuss Signed-off-by: Benoît Monin Reviewed-by: Paul Cercueil Cc: Signed-off-by: Jonathan Cameron --- drivers/iio/industrialio-buffer.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c index 46f36a6ed271..5c3df993bea2 100644 --- a/drivers/iio/industrialio-buffer.c +++ b/drivers/iio/industrialio-buffer.c @@ -1909,6 +1909,7 @@ static int iio_buffer_enqueue_dmabuf(struct iio_dev_buffer_pair *ib, dma_resv_add_fence(dmabuf->resv, &fence->base, dma_to_ram ? DMA_RESV_USAGE_WRITE : DMA_RESV_USAGE_READ); + dma_fence_put(&fence->base); dma_resv_unlock(dmabuf->resv); cookie = dma_fence_begin_signalling(); -- 2.54.0