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The commit637bc8bbe6("inet: reset tb->fastreuseport when adding a reuseport sk") added a bind-address cache in tb->fast*. The tb->fast* caches the address of a sk which has successfully been binded with SO_REUSEPORT ON. The idea is to avoid the expensive conflict search in inet_csk_bind_conflict(). There is an issue with wildcard matching where sk_reuseport_match() should have returned false but it is currently returning true. It ends up hiding bind conflict. For example, bind("[::1]:443"); /* without SO_REUSEPORT. Succeed. */ bind("[::2]:443"); /* with SO_REUSEPORT. Succeed. */ bind("[::]:443"); /* with SO_REUSEPORT. Still Succeed where it shouldn't */ The last bind("[::]:443") with SO_REUSEPORT on should have failed because it should have a conflict with the very first bind("[::1]:443") which has SO_REUSEPORT off. However, the address "[::2]" is cached in tb->fast* in the second bind. In the last bind, the sk_reuseport_match() returns true because the binding sk's wildcard addr "[::]" matches with the "[::2]" cached in tb->fast*. The correct bind conflict is reported by removing the second bind such that tb->fast* cache is not involved and forces the bind("[::]:443") to go through the inet_csk_bind_conflict(): bind("[::1]:443"); /* without SO_REUSEPORT. Succeed. */ bind("[::]:443"); /* with SO_REUSEPORT. -EADDRINUSE */ The expected behavior for sk_reuseport_match() is, it should only allow the "cached" tb->fast* address to be used as a wildcard match but not the address of the binding sk. To do that, the current "bool match_wildcard" arg is split into "bool match_sk1_wildcard" and "bool match_sk2_wildcard". This change only affects the sk_reuseport_match() which is only used by inet_csk (e.g. TCP). The other use cases are calling inet_rcv_saddr_equal() and this patch makes it pass the same "match_wildcard" arg twice to the "ipv[46]_rcv_saddr_equal(..., match_wildcard, match_wildcard)". Cc: Josef Bacik <jbacik@fb.com> Fixes:637bc8bbe6("inet: reset tb->fastreuseport when adding a reuseport sk") Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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.