Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 28 Jun 2023 13:47:54 +0200 | From | Greg KH <> | Subject | Re: [PATCH v2] misc: bcm_vk: Fix potential deadlock on &vk->ctx_lock |
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On Wed, Jun 28, 2023 at 11:29:58AM +0000, Chengfeng Ye wrote: > As &vk->ctx_lock is acquired by timer bcm_vk_hb_poll() under softirq > context, other process context code should disable irq or bottom-half > before acquire the same lock, otherwise deadlock could happen if the > timer preempt the execution while the lock is held in process context > on the same CPU. > > Possible deadlock scenario > bcm_vk_open() > -> bcm_vk_get_ctx() > -> spin_lock(&vk->ctx_lock) > <timer iterrupt> > -> bcm_vk_hb_poll() > -> bcm_vk_blk_drv_access() > -> spin_lock_irqsave(&vk->ctx_lock, flags) (deadlock here) > > This flaw was found using an experimental static analysis tool we are > developing for irq-related deadlock, which reported the following > warning when analyzing the linux kernel 6.4-rc7 release. > > [Deadlock]: &vk->ctx_lock > [Interrupt]: bcm_vk_hb_poll > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_msg.c:176 > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_dev.c:512 > [Locking Unit]: bcm_vk_ioctl > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_dev.c:1181 > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_dev.c:512 > > [Deadlock]: &vk->ctx_lock > [Interrupt]: bcm_vk_hb_poll > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_msg.c:176 > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_dev.c:512 > [Locking Unit]: bcm_vk_ioctl > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_dev.c:1169 > > [Deadlock]: &vk->ctx_lock > [Interrupt]: bcm_vk_hb_poll > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_msg.c:176 > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_dev.c:512 > [Locking Unit]: bcm_vk_open > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_msg.c:216 > > [Deadlock]: &vk->ctx_lock > [Interrupt]: bcm_vk_hb_poll > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_msg.c:176 > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_dev.c:512 > [Locking Unit]: bcm_vk_release > -->/root/linux/drivers/misc/bcm-vk/bcm_vk_msg.c:306 > > The tentative patch fix the potential deadlock by spin_lock_irqsave(). > > Signed-off-by: Chengfeng Ye <dg573847474@gmail.com> > ---
You do not mention how you tested to verify that your change is correct :(
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