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([2402:f000:1:1501:200:5efe:a66f:8b74]) by smtp.gmail.com with ESMTPSA id x4sm5309685pff.143.2019.12.18.18.32.22 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 18 Dec 2019 18:32:24 -0800 (PST) Subject: Re: [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp() To: Dominik Brodowski Cc: miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org References: <20191218140552.12249-1-baijiaju1990@gmail.com> <20191218172813.GA338501@light.dominikbrodowski.net> From: Jia-Ju Bai Message-ID: <42939a91-baab-54ad-bb4c-8a77e4418f2f@gmail.com> Date: Thu, 19 Dec 2019 10:32:24 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <20191218172813.GA338501@light.dominikbrodowski.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/12/19 1:28, Dominik Brodowski wrote: > On Wed, Dec 18, 2019 at 10:05:52PM +0800, Jia-Ju Bai wrote: >> The driver may sleep while holding a spinlock. >> The function call path (from bottom to top) in Linux 4.19 is: >> >> drivers/pcmcia/pcmcia_resource.c, 312: >> mutex_lock in pcmcia_fixup_vpp >> drivers/mtd/maps/pcmciamtd.c, 309: >> pcmcia_fixup_vpp in pcmciamtd_set_vpp >> drivers/mtd/maps/pcmciamtd.c, 306: >> _raw_spin_lock_irqsave in pcmciamtd_set_vpp >> >> drivers/pcmcia/pcmcia_resource.c, 312: >> mutex_lock in pcmcia_fixup_vpp >> drivers/mtd/maps/pcmciamtd.c, 312: >> pcmcia_fixup_vpp in pcmciamtd_set_vpp >> drivers/mtd/maps/pcmciamtd.c, 306: >> _raw_spin_lock_irqsave in pcmciamtd_set_vp >> >> mutex_lock() may sleep at runtime. > Thanks for noticing this issue. > >> To fix these bugs, pcmcia_fixup_vpp() is called without holding the >> spinlock. > I don't think that this is the right approach here -- we lose the protection > against races in calls to pcmcia_fixup_vpp(). Instead, we should change the > spinlock to a mutex, which seems to be sufficient here. Could you prepare > such a patch, please? Okay, thanks for the advice :) I will send a new patch. Best wishes, Jia-Ju Bai