linux.git/kernel/bpf/sockmap.c, branch v4.19-rc2

bpf: sockmap: write_space events need to be passed to TCP handler

2018-08-22T19:58:20+00:00

When sockmap code is using the stream parser it also handles the write
space events in order to handle the case where (a) verdict redirects
skb to another socket and (b) the sockmap then sends the skb but due
to memory constraints (or other EAGAIN errors) needs to do a retry.

But the initial code missed a third case where the
skb_send_sock_locked() triggers an sk_wait_event(). A typically case
would be when sndbuf size is exceeded. If this happens because we
do not pass the write_space event to the lower layers we never wake
up the event and it will wait for sndtimeo. Which as noted in ktls
fix may be rather large and look like a hang to the user.

To reproduce the best test is to reduce the sndbuf size and send
1B data chunks to stress the memory handling. To fix this pass the
event from the upper layer to the lower layer.

Signed-off-by: John Fastabend 
Signed-off-by: Daniel Borkmann

bpf, sockmap: fix sock hash count in alloc_sock_hash_elem

2018-08-22T18:35:18+00:00

When we try to allocate a new sock hash entry and the allocation
fails, then sock hash map fails to reduce the map element counter,
meaning we keep accounting this element although it was never used.
Fix it by dropping the element counter on error.

Fixes: 81110384441a ("bpf: sockmap, add hash map support")
Signed-off-by: Daniel Borkmann 
Acked-by: John Fastabend

bpf, sockmap: fix sock_hash_alloc and reject zero-sized keys

2018-08-22T18:34:51+00:00

Currently, it is possible to create a sock hash map with key size
of 0 and have the kernel return a fd back to user space. This is
invalid for hash maps (and kernel also hasn't been tested for zero
key size support in general at this point). Thus, reject such
configuration.

Fixes: 81110384441a ("bpf: sockmap, add hash map support")
Signed-off-by: Daniel Borkmann 
Acked-by: John Fastabend 
Acked-by: Song Liu

bpf, sockmap: fix sock_map_ctx_update_elem race with exist/noexist

2018-08-16T21:58:08+00:00

The current code in sock_map_ctx_update_elem() allows for BPF_EXIST
and BPF_NOEXIST map update flags. While on array-like maps this approach
is rather uncommon, e.g. bpf_fd_array_map_update_elem() and others
enforce map update flags to be BPF_ANY such that xchg() can be used
directly, the current implementation in sock map does not guarantee
that such operation with BPF_EXIST / BPF_NOEXIST is atomic.

The initial test does a READ_ONCE(stab->sock_map[i]) to fetch the
socket from the slot which is then tested for NULL / non-NULL. However
later after __sock_map_ctx_update_elem(), the actual update is done
through osock = xchg(&stab->sock_map[i], sock). Problem is that in
the meantime a different CPU could have updated / deleted a socket
on that specific slot and thus flag contraints won't hold anymore.

I've been thinking whether best would be to just break UAPI and do
an enforcement of BPF_ANY to check if someone actually complains,
however trouble is that already in BPF kselftest we use BPF_NOEXIST
for the map update, and therefore it might have been copied into
applications already. The fix to keep the current behavior intact
would be to add a map lock similar to the sock hash bucket lock only
for covering the whole map.

Fixes: 174a79ff9515 ("bpf: sockmap with sk redirect support")
Signed-off-by: Daniel Borkmann 
Acked-by: John Fastabend 
Acked-by: Song Liu 
Signed-off-by: Alexei Starovoitov

bpf, sockmap: fix map elem deletion race with smap_stop_sock

2018-08-16T21:58:08+00:00

The smap_start_sock() and smap_stop_sock() are each protected under
the sock->sk_callback_lock from their call-sites except in the case
of sock_map_delete_elem() where we drop the old socket from the map
slot. This is racy because the same sock could be part of multiple
sock maps, so we run smap_stop_sock() in parallel, and given at that
point psock->strp_enabled might be true on both CPUs, we might for
example wrongly restore the sk->sk_data_ready / sk->sk_write_space.
Therefore, hold the sock->sk_callback_lock as well on delete. Looks
like 2f857d04601a ("bpf: sockmap, remove STRPARSER map_flags and add
multi-map support") had this right, but later on e9db4ef6bf4c ("bpf:
sockhash fix omitted bucket lock in sock_close") removed it again
from delete leaving this smap_stop_sock() instance unprotected.

Fixes: e9db4ef6bf4c ("bpf: sockhash fix omitted bucket lock in sock_close")
Signed-off-by: Daniel Borkmann 
Acked-by: John Fastabend 
Acked-by: Song Liu 
Signed-off-by: Alexei Starovoitov

bpf, sockmap: fix leakage of smap_psock_map_entry

2018-08-16T21:58:08+00:00

While working on sockmap I noticed that we do not always kfree the
struct smap_psock_map_entry list elements which track psocks attached
to maps. In the case of sock_hash_ctx_update_elem(), these map entries
are allocated outside of __sock_map_ctx_update_elem() with their
linkage to the socket hash table filled. In the case of sock array,
the map entries are allocated inside of __sock_map_ctx_update_elem()
and added with their linkage to the psock->maps. Both additions are
under psock->maps_lock each.

Now, we drop these elements from their psock->maps list in a few
occasions: i) in sock array via smap_list_map_remove() when an entry
is either deleted from the map from user space, or updated via
user space or BPF program where we drop the old socket at that map
slot, or the sock array is freed via sock_map_free() and drops all
its elements; ii) for sock hash via smap_list_hash_remove() in exactly
the same occasions as just described for sock array; iii) in the
bpf_tcp_close() where we remove the elements from the list via
psock_map_pop() and iterate over them dropping themselves from either
sock array or sock hash; and last but not least iv) once again in
smap_gc_work() which is a callback for deferring the work once the
psock refcount hit zero and thus the socket is being destroyed.

Problem is that the only case where we kfree() the list entry is
in case iv), which at that point should have an empty list in
normal cases. So in cases from i) to iii) we unlink the elements
without freeing where they go out of reach from us. Hence fix is
to properly kfree() them as well to stop the leakage. Given these
are all handled under psock->maps_lock there is no need for deferred
RCU freeing.

I later also ran with kmemleak detector and it confirmed the finding
as well where in the state before the fix the object goes unreferenced
while after the patch no kmemleak report related to BPF showed up.

  [...]
  unreferenced object 0xffff880378eadae0 (size 64):
    comm "test_sockmap", pid 2225, jiffies 4294720701 (age 43.504s)
    hex dump (first 32 bytes):
      00 01 00 00 00 00 ad de 00 02 00 00 00 00 ad de  ................
      50 4d 75 5d 03 88 ff ff 00 00 00 00 00 00 00 00  PMu]............
    backtrace:
      [<000000005225ac3c>] sock_map_ctx_update_elem.isra.21+0xd8/0x210
      [<0000000045dd6d3c>] bpf_sock_map_update+0x29/0x60
      [<00000000877723aa>] ___bpf_prog_run+0x1e1f/0x4960
      [<000000002ef89e83>] 0xffffffffffffffff
  unreferenced object 0xffff880378ead240 (size 64):
    comm "test_sockmap", pid 2225, jiffies 4294720701 (age 43.504s)
    hex dump (first 32 bytes):
      00 01 00 00 00 00 ad de 00 02 00 00 00 00 ad de  ................
      00 44 75 5d 03 88 ff ff 00 00 00 00 00 00 00 00  .Du]............
    backtrace:
      [<000000005225ac3c>] sock_map_ctx_update_elem.isra.21+0xd8/0x210
      [<0000000030e37a3a>] sock_map_update_elem+0x125/0x240
      [<000000002e5ce36e>] map_update_elem+0x4eb/0x7b0
      [<00000000db453cc9>] __x64_sys_bpf+0x1f9/0x360
      [<0000000000763660>] do_syscall_64+0x9a/0x300
      [<00000000422a2bb2>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
      [<000000002ef89e83>] 0xffffffffffffffff
  [...]

Fixes: e9db4ef6bf4c ("bpf: sockhash fix omitted bucket lock in sock_close")
Fixes: 54fedb42c653 ("bpf: sockmap, fix smap_list_map_remove when psock is in many maps")
Fixes: 2f857d04601a ("bpf: sockmap, remove STRPARSER map_flags and add multi-map support")
Signed-off-by: Daniel Borkmann 
Acked-by: John Fastabend 
Acked-by: Song Liu 
Signed-off-by: Alexei Starovoitov

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2018-08-13T17:07:23+00:00

Daniel Borkmann says:

====================
pull-request: bpf-next 2018-08-13

The following pull-request contains BPF updates for your *net-next* tree.

The main changes are:

1) Add driver XDP support for veth. This can be used in conjunction with
   redirect of another XDP program e.g. sitting on NIC so the xdp_frame
   can be forwarded to the peer veth directly without modification,
   from Toshiaki.

2) Add a new BPF map type REUSEPORT_SOCKARRAY and prog type SK_REUSEPORT
   in order to provide more control and visibility on where a SO_REUSEPORT
   sk should be located, and the latter enables to directly select a sk
   from the bpf map. This also enables map-in-map for application migration
   use cases, from Martin.

3) Add a new BPF helper bpf_skb_ancestor_cgroup_id() that returns the id
   of cgroup v2 that is the ancestor of the cgroup associated with the
   skb at the ancestor_level, from Andrey.

4) Implement BPF fs map pretty-print support based on BTF data for regular
   hash table and LRU map, from Yonghong.

5) Decouple the ability to attach BTF for a map from the key and value
   pretty-printer in BPF fs, and enable further support of BTF for maps for
   percpu and LPM trie, from Daniel.

6) Implement a better BPF sample of using XDP's CPU redirect feature for
   load balancing SKB processing to remote CPU. The sample implements the
   same XDP load balancing as Suricata does which is symmetric hash based
   on IP and L4 protocol, from Jesper.

7) Revert adding NULL pointer check with WARN_ON_ONCE() in __xdp_return()'s
   critical path as it is ensured that the allocator is present, from Björn.
====================

Signed-off-by: David S. Miller

bpf: decouple btf from seq bpf fs dump and enable more maps

2018-08-12T22:52:45+00:00

Commit a26ca7c982cb ("bpf: btf: Add pretty print support to
the basic arraymap") and 699c86d6ec21 ("bpf: btf: add pretty
print for hash/lru_hash maps") enabled support for BTF and
dumping via BPF fs for array and hash/lru map. However, both
can be decoupled from each other such that regular BPF maps
can be supported for attaching BTF key/value information,
while not all maps necessarily need to dump via map_seq_show_elem()
callback.

The basic sanity check which is a prerequisite for all maps
is that key/value size has to match in any case, and some maps
can have extra checks via map_check_btf() callback, e.g.
probing certain types or indicating no support in general. With
that we can also enable retrieving BTF info for per-cpu map
types and lpm.

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Acked-by: Yonghong Song

Merge ra.kernel.org:/pub/scm/linux/kernel/git/davem/net

2018-08-12T00:52:00+00:00

bpf, sockmap: fix leak in bpf_tcp_sendmsg wait for mem path

2018-08-08T19:06:17+00:00

In bpf_tcp_sendmsg() the sk_alloc_sg() may fail. In the case of
ENOMEM, it may also mean that we've partially filled the scatterlist
entries with pages. Later jumping to sk_stream_wait_memory()
we could further fail with an error for several reasons, however
we miss to call free_start_sg() if the local sk_msg_buff was used.

Fixes: 4f738adba30a ("bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data")
Signed-off-by: Daniel Borkmann 
Acked-by: John Fastabend 
Signed-off-by: Alexei Starovoitov