Re: [PATCH] virtio_pci_modern: don't sleep in atomic context in admin cmd submission

[sashiko-bot@kernel.org]

> virtqueue_exec_admin_cmd() calls virtqueue_add_sgs() with GFP_KERNEL while
> holding admin_vq->lock, which is taken with spin_lock_irqsave(). The admin
> virtqueue is created with ctx=false, so when the device has negotiated
> VIRTIO_RING_F_INDIRECT_DESC it uses indirect descriptors and
> virtqueue_add() allocates the indirect descriptor table with the passed
> gfp. Admin commands always have more than one sg (header plus status), so
> the indirect path is taken and a GFP_KERNEL allocation may sleep while
> interrupts are disabled under the spinlock, triggering a "BUG: sleeping
> function called from invalid context" splat with CONFIG_DEBUG_ATOMIC_SLEEP.
> 
> Use GFP_ATOMIC for the descriptor allocation that runs under the lock; the
> table is small and the -ENOMEM path is already handled.
> 
> Fixes: 4c3b54af907e ("virtio_pci_modern: use completion instead of busy loop to wait on admin cmd result")
> Cc: stable@vger.kernel.org
> Signed-off-by: Hyunjung Ko <hj351016@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261111075154.3017978-1-hj351016@gmail.com?part=1