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[143.89.191.97]) by smtp.gmail.com with ESMTPSA id u5-20020aa78485000000b00671eb039b23sm4410638pfn.58.2023.06.27.09.43.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jun 2023 09:43:27 -0700 (PDT) From: Chengfeng Ye To: sean.wang@mediatek.com, vkoul@kernel.org, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com Cc: dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, Chengfeng Ye Subject: [PATCH] dmaengine: mediatek: mtk-hsdma: fix potential deadlock on &vc->lock Date: Tue, 27 Jun 2023 16:43:09 +0000 Message-Id: <20230627164309.59922-1-dg573847474@gmail.com> X-Mailer: git-send-email 2.17.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" As &vc->lock is acquired by the irq mtk_hsdma_irq(), other process context code acquiring the lock should disable irq. The terminate callback mtk_hsdma_terminate_all() acquires the same lock without closing irq. Possible deadlock scenario: mtk_hsdma_free_active_desc() -> spin_lock(&hvc->vc.lock) -> mtk_hsdma_irq() -> mtk_hsdma_free_rooms_in_ring() -> spin_lock(&hvc->vc.lock) (deadlock here) This flaw was found using an experimental static analysis tool we are developing for irq-related deadlock. The tentative patch fix the potential deadlock by spin_lock_irqsave(). Signed-off-by: Chengfeng Ye --- drivers/dma/mediatek/mtk-hsdma.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/dma/mediatek/mtk-hsdma.c b/drivers/dma/mediatek/mtk-hs= dma.c index 69cc61c0b262..6b6773575893 100644 --- a/drivers/dma/mediatek/mtk-hsdma.c +++ b/drivers/dma/mediatek/mtk-hsdma.c @@ -757,18 +757,19 @@ static void mtk_hsdma_free_active_desc(struct dma_cha= n *c) { struct mtk_hsdma_vchan *hvc =3D to_hsdma_vchan(c); bool sync_needed =3D false; + unsigned long flags; =20 /* * Once issue_synchronize is being set, which means once the hardware * consumes all descriptors for the channel in the ring, the * synchronization must be notified immediately it is completed. */ - spin_lock(&hvc->vc.lock); + spin_lock_irqsave(&hvc->vc.lock, flags); if (!list_empty(&hvc->desc_hw_processing)) { hvc->issue_synchronize =3D true; sync_needed =3D true; } - spin_unlock(&hvc->vc.lock); + spin_unlock_irqrestore(&hvc->vc.lock, flags); =20 if (sync_needed) wait_for_completion(&hvc->issue_completion); --=20 2.17.1