Merge branch 'fix-sockmap'

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John Fastabend says:

====================
Fix a splat introduced by recent changes to avoid skipping ingress policy
when kTLS is enabled. The RCU splat was introduced because in the non-TLS
case the caller is wrapped in an rcu_read_lock/unlock. But, in the TLS
case we have a reference to the psock and the caller did not wrap its
call in rcu_read_lock/unlock.

To fix extend the RCU section to include the redirect case which was
missed. From v1->v2 I changed the location a bit to simplify the code
some. See patch 1.

But, then Martin asked why it was not needed in the non-TLS case. The
answer for patch 1 was, as stated above, because the caller has the
rcu read lock. However, there was still a missing case where a BPF
user could in-theory line up a set of parameters to hit a case
where the code was entered from strparser side from a different context
then the initial caller. To hit this user would need a parser program
to return value greater than skb->len then an ENOMEM error could happen
in the strparser codepath triggering strparser to retry from a workqueue
and without rcu_read_lock original caller used. See patch 2 for details.

Finally, we don't actually have any selftests for parser returning a
value geater than skb->len so add one in patch 3. This is especially
needed because at least I don't have any code that uses the parser
to return value greater than skb->len. So I wouldn't have caught any
errors here in my own testing.

Thanks, John

v1->v2: simplify code in patch 1 some and add patches 2 and 3.
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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This commit is contained in:

Alexei Starovoitov 2020-06-28 08:33:28 -07:00

parent 7a64135f32 53792fa45b

commit 2bdeb3ed54

3 changed files with 40 additions and 9 deletions

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23

net/core/skmsg.c

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8

tools/testing/selftests/bpf/progs/test_sockmap_kern.h

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18

tools/testing/selftests/bpf/test_sockmap.c

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