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3e104c2381
When sk_msg_pop() is called where the pop operation is working on
the end of a sge element and there is no additional trailing data
and there _is_ data in front of pop, like the following case,
|____________a_____________|__pop__|
We have out of order operations where we incorrectly set the pop
variable so that instead of zero'ing pop we incorrectly leave it
untouched, effectively. This can cause later logic to shift the
buffers around believing it should pop extra space. The result is
we have 'popped' more data then we expected potentially breaking
program logic.
It took us a while to hit this case because typically we pop headers
which seem to rarely be at the end of a scatterlist elements but
we can't rely on this.
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>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/158861288359.14306.7654891716919968144.stgit@john-Precision-5820-Tower
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.