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store: Avoid access to Forgotten() before configured #1599

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@ktock ktock commented Mar 11, 2024

Fixes #1594

Our Lookup() implementation returns a newly created *fusefs.Inode to go-fuse. Then that *fusefs.Inode is configured and managed by go-fuse lib.

Though *fusefs.Inode.Forgotten() allows status check of that object, it shouldn't be called until that *fusefs.Inode is fully configured by go-fuse. Otherwize we hit issue like #1594.

To avoid this race, this commit adds a lock for avoiding calling *fusefs.Inode.Forgotten() during configuration on-going in go-fuse.

Our `Lookup()` implementation returns a newly created `*fusefs.Inode` to
go-fuse. Then that `*fusefs.Inode` is configured and managed by go-fuse lib.

Though [`*fusefs.Inode.Forgotten()`](https://github.com/hanwen/go-fuse/blob/e9e7c22af17af4611b5783a16458647088cc8dec/fs/inode.go#L258)
allows status check of that object, it shouldn't be called until that
`*fusefs.Inode` is [fully configured by
go-fuse](https://github.com/hanwen/go-fuse/blob/e9e7c22af17af4611b5783a16458647088cc8dec/fs/bridge.go#L209-L210).

To avoid this race, this commit adds a lock for avoiding calling Forgotten API
during configuration on-going in go-fuse.

Signed-off-by: Kohei Tokunaga <[email protected]>
@ktock ktock changed the title Avoid access to Forgotten() before initialized Avoid access to Forgotten() before configured Mar 11, 2024
@ktock ktock changed the title Avoid access to Forgotten() before configured store: Avoid access to Forgotten() before configured Mar 11, 2024
@iain-macdonald
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iain-macdonald commented Mar 11, 2024

My understanding of the interactions between the go-fuse and stargz-snapshotter parts of the code may be off here, but won't the RLock/RUnlock calls in fsLocker surround the Lock/Unlock calls nested in newNodeWithID, causing deadlock? And if not, then isn't the lock in releasable insufficient as it doesn't guard the entire period from creation to initialization?

I think a simpler fix would be to used Inode.changeCounter to detect when an Inode hasn't been initialized and pair that with the Forgotten() check that's already present. I asked about this possibility in hanwen/go-fuse#504, so what would you think about seeing what Han-Wen says and then coming up with a more elaborate solution if that doesn't work?

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ktock commented Oct 8, 2024

Fixed in #1808.

@ktock ktock closed this Oct 8, 2024
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ino reuse in newInodeWithID
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