Re: [PATCH] fix race in mark_mounts_for_expiry()
From: Miklos Szeredi
Date: Wed May 18 2005 - 07:12:05 EST
> What you're doing is tricky. It's asking for a race.
I know. The comment above the function is there to make sure the user
is aware of this.
> Admittedly, it may not
> occur in the particular situation you're looking at, but can you always
> guarantee that?
Yes, if it's always called under lock.
> Remember, it may be a race against some piece of code that's not yet
> written, by an author who doesn't realise what _you_ are doing here
> because their changeset doesn't intersect with yours.
> Remember: you have, in effect, made the usage count on that structure
But _only after_ it's has gone to zero. When in fact there are no
more references to it, so it shouldn't matter.
The fact that it does matter and that mark_mounts_for_expiry()
derefences mnt->mnt_namespace without actually having a proper
reference to the namespace is the real culprit here.
This is the third bug found by Jamie Lokier, Ram and me in the
mnt_namespace change. So if we are looking at proper solutions I
think that is what we should be examining.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/