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struct ethtool_link_settings tends to be used as a header for other structures that have trailing bytes[1], but has a trailing flexible array itself. Using this overlapped with other structures leads to ambiguous object sizing in the compiler, so we want to avoid such situations (which have caused real bugs in the past). Detecting this can be done with -Wflex-array-member-not-at-end, which will need to be enabled globally. Using a tagged struct_group() to create a new ethtool_link_settings_hdr structure isn't possible as it seems we cannot use the tagged variant of struct_group() due to syntax issues from C++'s perspective (even within "extern C")[2]. Instead, we can just leave the offending member defined in UAPI and remove it from the kernel's view of the structure, as Linux doesn't actually use this member at all. There is also no change in size since it was already a flexible array that didn't contribute to size returned by any use of sizeof(). Reported-by: Jakub Kicinski <kuba@kernel.org> Closes: https://lore.kernel.org/lkml/20241109100213.262a2fa0@kernel.org/ [2] Link: https://lore.kernel.org/lkml/0bc2809fe2a6c11dd4c8a9a10d9bd65cccdb559b.1730238285.git.gustavoars@kernel.org/ [1] Signed-off-by: Kees Cook <kees@kernel.org> Reviewed-by: Jakub Kicinski <kuba@kernel.org> Link: https://patch.msgid.link/20241115204308.3821419-3-kees@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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.