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commitd5f6545934upstream. In commitb7213ffa0e("qnx4: avoid stringop-overread errors") I tried to teach gcc about how the directory entry structure can be two different things depending on a status flag. It made the code clearer, and it seemed to make gcc happy. However, Arnd points to a gcc bug, where despite using two different members of a union, gcc then gets confused, and uses the size of one of the members to decide if a string overrun happens. And not necessarily the rigth one. End result: with some configurations, gcc-11 will still complain about the source buffer size being overread: fs/qnx4/dir.c: In function 'qnx4_readdir': fs/qnx4/dir.c:76:32: error: 'strnlen' specified bound [16, 48] exceeds source size 1 [-Werror=stringop-overread] 76 | size = strnlen(name, size); | ^~~~~~~~~~~~~~~~~~~ fs/qnx4/dir.c:26:22: note: source object declared here 26 | char de_name; | ^~~~~~~ because gcc will get confused about which union member entry is actually getting accessed, even when the source code is very clear about it. Gcc internally will have combined two "redundant" pointers (pointing to different union elements that are at the same offset), and takes the size checking from one or the other - not necessarily the right one. This is clearly a gcc bug, but we can work around it fairly easily. The biggest thing here is the big honking comment about why we do what we do. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6 Reported-and-tested-by: Arnd Bergmann <arnd@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
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.