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commit7361d44896upstream. When user returns SK_DROP we need to reset the number of copied bytes to indicate to the user the bytes were dropped and not sent. If we don't reset the copied arg sendmsg will return as if those bytes were copied giving the user a positive return value. This works as expected today except in the case where the user also pops bytes. In the pop case the sg.size is reduced but we don't correctly account for this when copied bytes is reset. The popped bytes are not accounted for and we return a small positive value potentially confusing the user. The reason this happens is due to a typo where we do the wrong comparison when accounting for pop bytes. In this fix notice the if/else is not needed and that we have a similar problem if we push data except its not visible to the user because if delta is larger the sg.size we return a negative value so it appears as an error regardless. Fixes:7246d8ed4d("bpf: helper to pop data from messages") Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/bpf/20200111061206.8028-9-john.fastabend@gmail.com 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.
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.