db/hash_page.c: Reswap memory buffer in __put_page when dealing with a different byte order

[bnovkov]

Summary

__put_page appropriately swaps the contents of its in-memory buffers
when operating on a database that was created on a machine with a
different byte order. However, it does not revert the buffer to its
original state, leading to a corrupted buffer and possible
database corruption.

Address this by "unswapping" the buffer before returning from the function.

Sponsored by: Klara, Inc.
Inspired by: https://github.com/apple-oss-distributions/Libc

[markj]

lib/libc/db/hash/hash_page.c

584

Here we're copying the caller-supplied buffer onto the stack and byte-swapping that, so I don't think there's any purpose in restoring the original order?

[bnovkov]

lib/libc/db/hash/hash_page.c

584

oh, I hadn't noticed that memcpy, thanks!

In that case yes, there's no need to restore the order.
I'll go ahead and abandon the revision.