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[ Upstream commit9c3de619e1] When receiving netlink messages, libbpf was using a statically allocated stack buffer of 4k bytes. This happened to work fine on systems with a 4k page size, but on systems with larger page sizes it can lead to truncated messages. The user-visible impact of this was that libbpf would insist no XDP program was attached to some interfaces because that bit of the netlink message got chopped off. Fix this by switching to a dynamically allocated buffer; we borrow the approach from iproute2 of using recvmsg() with MSG_PEEK|MSG_TRUNC to get the actual size of the pending message before receiving it, adjusting the buffer as necessary. While we're at it, also add retries on interrupted system calls around the recvmsg() call. v2: - Move peek logic to libbpf_netlink_recv(), don't double free on ENOMEM. Fixes:8bbb77b7c7("libbpf: Add various netlink helpers") Reported-by: Zhiqian Guan <zhguan@redhat.com> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/bpf/20220211234819.612288-1-toke@redhat.com Signed-off-by: Sasha Levin <sashal@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 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.