epoll: Keep a reference on files added to the check list

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When adding a new fd to an epoll, and that this new fd is an
epoll fd itself, we recursively scan the fds attached to it
to detect cycles, and add non-epool files to a "check list"
that gets subsequently parsed.

However, this check list isn't completely safe when deletions
can happen concurrently. To sidestep the issue, make sure that
a struct file placed on the check list sees its f_count increased,
ensuring that a concurrent deletion won't result in the file
disapearing from under our feet.

Cc: stable@vger.kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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Marc Zyngier 2020-08-19 17:12:17 +01:00 • committed by Al Viro

parent 9123e3a74e

commit a9ed4a6560

1 changed files with 9 additions and 2 deletions

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fs/eventpoll.c

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