Close our side of memfd #88
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Sending a file descriptor through a socket effectively duplicates the file descriptor; it does not move the file descriptor out of the current process. Hence we need to close our side of the file descriptor explicitly to avoid leaking file descriptors.
lucab
approved these changes
Nov 8, 2021
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Ouch! Good find. Did you spot this on a running process? Does it need a minor bugfix release on its own? |
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No I found this accidentally. It only occurs for very large messages. But still, I'd like to fix it 🙂 |
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Thanks for merging. I don't think it's that urgent, so I'd make #87 next and then cut a new release? |
dfreese
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Dec 23, 2022
This was added in lucab#88, however, drop is already implicitly called on all objects when they go out of scope. This, for memfd happens a couple lines later, so the drop is redundant. The primary problem that lucab#88 solved was changing `into_raw_fd()` to `as_raw_fd()`, which no longer transferred ownership, requiring a manual close. From the [std::os::fd::IntoRawFd](https://doc.rust-lang.org/stable/std/os/fd/trait.IntoRawFd.html) docs: > This function is typically used to transfer ownership of the underlying file descriptor to the caller. When used in this way, callers are then the unique owners of the file descriptor and must close it once it’s no longer needed. It seems that the primary problem that close was not being called on memfd when it was consumed into a RawFd.
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Sending a file descriptor through a socket effectively duplicates the
file descriptor; it does not move the file descriptor out of the current
process.
Hence we need to close our side of the file descriptor explicitly to
avoid leaking file descriptors.