Re: [PATCH 0/2] kernfs, autofs: fix pipe lock cycles through sysfs stores

[Tejun Heo]

Hello, Krystian.

On Wed, Oct 21, 2026 at 02:51:48PM +0200, Krystian Kaniewski wrote:
> syzbot reports a lockdep cycle &pipe->mutex --> &of->mutex -->
> &sbi->pipe_mutex. splice holds a pipe mutex while it calls the write or
> read handler of a kernfs file, kernfs takes of->mutex there, and a write
> to /sys/power/resume looks up a path that can make autofs write a request
> into its daemon pipe and wait for the daemon.

This is an extremely convoluted case that isn't going to happen in any
realistic scenario, and it doesn't make sense to change the locking scheme
for it. Can we just disallow splice on /sys/power/resume instead?

Thanks.

--
tejun