linux-kernel - RE: [PATCH v3 vfio 3/3] pds/vfio: Fix possible sleep while in atomic context

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Message-ID: <BN9PR11MB52769E037CB356AB15A0D9B88CA0A@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Tue, 31 Oct 2023 06:14:45 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Brett Creeley <brett.creeley@....com>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        "yishaih@...dia.com" <yishaih@...dia.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "dan.carpenter@...aro.org" <dan.carpenter@...aro.org>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "shannon.nelson@....com" <shannon.nelson@....com>
Subject: RE: [PATCH v3 vfio 3/3] pds/vfio: Fix possible sleep while in atomic
 context

> From: Brett Creeley <brett.creeley@....com>
> Sent: Saturday, October 28, 2023 6:37 AM
> 
> The driver could possibly sleep while in atomic context resulting
> in the following call trace while CONFIG_DEBUG_ATOMIC_SLEEP=y is
> set:
> 
> BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:283
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2817, name: bash
> preempt_count: 1, expected: 0
> RCU nest depth: 0, expected: 0
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x36/0x50
>  __might_resched+0x123/0x170
>  mutex_lock+0x1e/0x50
>  pds_vfio_put_lm_file+0x1e/0xa0 [pds_vfio_pci]
>  pds_vfio_put_save_file+0x19/0x30 [pds_vfio_pci]
>  pds_vfio_state_mutex_unlock+0x2e/0x80 [pds_vfio_pci]
>  pci_reset_function+0x4b/0x70
>  reset_store+0x5b/0xa0
>  kernfs_fop_write_iter+0x137/0x1d0
>  vfs_write+0x2de/0x410
>  ksys_write+0x5d/0xd0
>  do_syscall_64+0x3b/0x90
>  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
> 
> This can happen if pds_vfio_put_restore_file() and/or
> pds_vfio_put_save_file() grab the mutex_lock(&lm_file->lock)
> while the spin_lock(&pds_vfio->reset_lock) is held, which can
> happen during while calling pds_vfio_state_mutex_unlock().
> 
> Fix this by changing the reset_lock to reset_mutex so there are no such
> conerns. Also, make sure to destroy the reset_mutex in the driver specific
> VFIO device release function.
> 
> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> Closes: https://lore.kernel.org/kvm/1f9bc27b-3de9-4891-9687-
> ba2820c1b390@...oto.mountain/
> Signed-off-by: Brett Creeley <brett.creeley@....com>
> Reviewed-by: Shannon Nelson <shannon.nelson@....com>

better change all three drivers together...