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Some file systems (e.g. ext4) may reuse inode numbers once the inode is
not in use anymore. Usually hostfs will keep an FD open for each inode,
but this is not always the case. In the case of sockets, this cannot
even be done properly.
As such, the following sequence of events was possible:
* application creates and deletes a socket
* hostfs creates/deletes the socket on the host
* inode is still in the hostfs cache
* hostfs creates a new file
* ext4 on the outside reuses the inode number
* hostfs finds the socket inode for the newly created file
* application receives -ENXIO when opening the file
As mentioned, this can only happen if the deleted file is a special file
that is never opened on the host (i.e. no .open fop).
As such, to prevent issues, it is sufficient to check that the inode
has the expected type. That said, also add a check for the inode birth
time, just to be on the safe side.
Fixes: 74ce793bcb ("hostfs: Fix ephemeral inodes")
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Reviewed-by: Mickaël Salaün <mic@digikod.net>
Tested-by: Mickaël Salaün <mic@digikod.net>
Link: https://patch.msgid.link/20250214092822.1241575-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.