On Thu, Nov 07, 2013 at 12:36:56AM +0000, Liu, Chuansheng wrote: > > > > -----Original Message----- > > From: Tejun Heo [mailto:hte...@gmail.com] On Behalf Of t...@kernel.org > > Sent: Thursday, November 07, 2013 8:30 AM > > To: Liu, Chuansheng > > Cc: Greg KH; dmitry.torok...@gmail.com; linux-kernel@vger.kernel.org > > Subject: Re: [PATCH] devres: Freeing the drs after all release() are called > > > > Hello, Liu. > > > > On Thu, Nov 07, 2013 at 12:27:56AM +0000, Liu, Chuansheng wrote: > > > The driver code is as below: > > > _INIT() { > > > > > > A = devm_kzalloc(); > > > B= devm_request_threaded_irq(isr_handler); > > > C = devm_kzalloc(); > > > } > > > > > > When driver _EXIT, the devres_release_all () will be called. > > > The C will be kfreed before B, but when freeing irq B, the pending > > > isr_handler() > > possibly > > > will access the memory B which has been freed. > > > Then the memory corruption occurred. > > > > > > This patch can solve this scenario. > > > > Isn't the bug there IRQ being requested before all its resources are > > allocated? The proposed change just masks the underlying issue or > > incorrectly ordered operations. > Yes, I knew I can put the code always like below: > A = devm_kzalloc(); > C = devm_kzalloc(); > ... > B= devm_request_threaded_irq(isr_handler); > > But, the above is just one simple coding prototype, if there are many calling: > E -- > F -- > D -- >... then to devm_kzalloc(). > > To be honest, it will make code too hard to always adapt the rule? > And I trying to find out every potential devm_kzalloc() before irq requesting.
Such code is already broken anyway and has to be fixed - if your IRQ handler accesses data allocated by devm_kzalloc that you call only _after_ you called devm_request_irq() then interrupt arriving at unfortunate moment will crash your driver at the probing stage. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
