linux-toradex.git/net/bpf, branch v4.20-rc3

bpf: add tests for direct packet access from CGROUP_SKB

2018-10-19T20:49:34+00:00

Tests are added to make sure CGROUP_SKB cannot access:
  tc_classid, data_meta, flow_keys

and can read and write:
  mark, prority, and cb[0-4]

and can read other fields.

To make selftest with skb->sk work, a dummy sk is added in
bpf_prog_test_run_skb().

Signed-off-by: Song Liu 
Signed-off-by: Alexei Starovoitov

bpf: extend cgroup bpf core to allow multiple cgroup storage types

2018-10-01T14:18:32+00:00

In order to introduce per-cpu cgroup storage, let's generalize
bpf cgroup core to support multiple cgroup storage types.
Potentially, per-node cgroup storage can be added later.

This commit is mostly a formal change that replaces
cgroup_storage pointer with a array of cgroup_storage pointers.
It doesn't actually introduce a new storage type,
it will be done later.

Each bpf program is now able to have one cgroup storage of each type.

Signed-off-by: Roman Gushchin 
Acked-by: Song Liu 
Cc: Daniel Borkmann 
Cc: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann

bpf/test_run: support cgroup local storage

2018-08-02T22:47:32+00:00

Allocate a temporary cgroup storage to use for bpf program test runs.

Because the test program is not actually attached to a cgroup,
the storage is allocated manually just for the execution
of the bpf program.

If the program is executed multiple times, the storage is not zeroed
on each run, emulating multiple runs of the program, attached to
a real cgroup.

Signed-off-by: Roman Gushchin 
Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Acked-by: Martin KaFai Lau 
Signed-off-by: Daniel Borkmann

bpf: fix panic due to oob in bpf_prog_test_run_skb

2018-07-11T23:10:57+00:00

sykzaller triggered several panics similar to the below:

  [...]
  [  248.851531] BUG: KASAN: use-after-free in _copy_to_user+0x5c/0x90
  [  248.857656] Read of size 985 at addr ffff8808017ffff2 by task a.out/1425
  [...]
  [  248.865902] CPU: 1 PID: 1425 Comm: a.out Not tainted 4.18.0-rc4+ #13
  [  248.865903] Hardware name: Supermicro SYS-5039MS-H12TRF/X11SSE-F, BIOS 2.1a 03/08/2018
  [  248.865905] Call Trace:
  [  248.865910]  dump_stack+0xd6/0x185
  [  248.865911]  ? show_regs_print_info+0xb/0xb
  [  248.865913]  ? printk+0x9c/0xc3
  [  248.865915]  ? kmsg_dump_rewind_nolock+0xe4/0xe4
  [  248.865919]  print_address_description+0x6f/0x270
  [  248.865920]  kasan_report+0x25b/0x380
  [  248.865922]  ? _copy_to_user+0x5c/0x90
  [  248.865924]  check_memory_region+0x137/0x190
  [  248.865925]  kasan_check_read+0x11/0x20
  [  248.865927]  _copy_to_user+0x5c/0x90
  [  248.865930]  bpf_test_finish.isra.8+0x4f/0xc0
  [  248.865932]  bpf_prog_test_run_skb+0x6a0/0xba0
  [...]

After scrubbing the BPF prog a bit from the noise, turns out it called
bpf_skb_change_head() for the lwt_xmit prog with headroom of 2. Nothing
wrong in that, however, this was run with repeat >> 0 in bpf_prog_test_run_skb()
and the same skb thus keeps changing until the pskb_expand_head() called
from skb_cow() keeps bailing out in atomic alloc context with -ENOMEM.
So upon return we'll basically have 0 headroom left yet blindly do the
__skb_push() of 14 bytes and keep copying data from there in bpf_test_finish()
out of bounds. Fix to check if we have enough headroom and if pskb_expand_head()
fails, bail out with error.

Another bug independent of this fix (but related in triggering above) is
that BPF_PROG_TEST_RUN should be reworked to reset the skb/xdp buffer to
it's original state from input as otherwise repeating the same test in a
loop won't work for benchmarking when underlying input buffer is getting
changed by the prog each time and reused for the next run leading to
unexpected results.

Fixes: 1cf1cae963c2 ("bpf: introduce BPF_PROG_TEST_RUN command")
Reported-by: syzbot+709412e651e55ed96498@syzkaller.appspotmail.com
Reported-by: syzbot+54f39d6ab58f39720a55@syzkaller.appspotmail.com
Signed-off-by: Daniel Borkmann 
Signed-off-by: Alexei Starovoitov

bpf: making bpf_prog_test run aware of possible data_end ptr change

2018-04-18T21:34:16+00:00

after introduction of bpf_xdp_adjust_tail helper packet length
could be changed not only if xdp->data pointer has been changed
but xdp->data_end as well. making bpf_prog_test_run aware of this
possibility

Signed-off-by: Nikita V. Shirokov 
Signed-off-by: Daniel Borkmann

bpf: fix null pointer deref in bpf_prog_test_run_xdp

2018-02-01T15:43:56+00:00

syzkaller was able to generate the following XDP program ...

  (18) r0 = 0x0
  (61) r5 = *(u32 *)(r1 +12)
  (04) (u32) r0 += (u32) 0
  (95) exit

... and trigger a NULL pointer dereference in ___bpf_prog_run()
via bpf_prog_test_run_xdp() where this was attempted to run.

Reason is that recent xdp_rxq_info addition to XDP programs
updated all drivers, but not bpf_prog_test_run_xdp(), where
xdp_buff is set up. Thus when context rewriter does the deref
on the netdev it's NULL at runtime. Fix it by using xdp_rxq
from loopback dev. __netif_get_rx_queue() helper can also be
reused in various other locations later on.

Fixes: 02dd3291b2f0 ("bpf: finally expose xdp_rxq_info to XDP bpf-programs")
Reported-by: syzbot+1eb094057b338eb1fc00@syzkaller.appspotmail.com
Signed-off-by: Daniel Borkmann 
Cc: Jesper Dangaard Brouer 
Acked-by: Jesper Dangaard Brouer 
Signed-off-by: Alexei Starovoitov

bpf: add meta pointer for direct access

2017-09-26T20:36:44+00:00

This work enables generic transfer of metadata from XDP into skb. The
basic idea is that we can make use of the fact that the resulting skb
must be linear and already comes with a larger headroom for supporting
bpf_xdp_adjust_head(), which mangles xdp->data. Here, we base our work
on a similar principle and introduce a small helper bpf_xdp_adjust_meta()
for adjusting a new pointer called xdp->data_meta. Thus, the packet has
a flexible and programmable room for meta data, followed by the actual
packet data. struct xdp_buff is therefore laid out that we first point
to data_hard_start, then data_meta directly prepended to data followed
by data_end marking the end of packet. bpf_xdp_adjust_head() takes into
account whether we have meta data already prepended and if so, memmove()s
this along with the given offset provided there's enough room.

xdp->data_meta is optional and programs are not required to use it. The
rationale is that when we process the packet in XDP (e.g. as DoS filter),
we can push further meta data along with it for the XDP_PASS case, and
give the guarantee that a clsact ingress BPF program on the same device
can pick this up for further post-processing. Since we work with skb
there, we can also set skb->mark, skb->priority or other skb meta data
out of BPF, thus having this scratch space generic and programmable
allows for more flexibility than defining a direct 1:1 transfer of
potentially new XDP members into skb (it's also more efficient as we
don't need to initialize/handle each of such new members). The facility
also works together with GRO aggregation. The scratch space at the head
of the packet can be multiple of 4 byte up to 32 byte large. Drivers not
yet supporting xdp->data_meta can simply be set up with xdp->data_meta
as xdp->data + 1 as bpf_xdp_adjust_meta() will detect this and bail out,
such that the subsequent match against xdp->data for later access is
guaranteed to fail.

The verifier treats xdp->data_meta/xdp->data the same way as we treat
xdp->data/xdp->data_end pointer comparisons. The requirement for doing
the compare against xdp->data is that it hasn't been modified from it's
original address we got from ctx access. It may have a range marking
already from prior successful xdp->data/xdp->data_end pointer comparisons
though.

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Acked-by: John Fastabend 
Signed-off-by: David S. Miller

bpf: rename bpf_compute_data_end into bpf_compute_data_pointers

2017-09-26T20:36:44+00:00

Just do the rename into bpf_compute_data_pointers() as we'll add
one more pointer here to recompute.

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Acked-by: John Fastabend 
Signed-off-by: David S. Miller

bpf: Align packet data properly in program testing framework.

2017-05-02T15:46:28+00:00

Make sure we apply NET_IP_ALIGN when reserving headroom for SKB
and XDP test runs, just like a real driver would.

Signed-off-by: David S. Miller 
Acked-by: Daniel Borkmann

bpf: Do not dereference user pointer in bpf_test_finish().

2017-05-02T15:46:28+00:00

Instead, pass the kattr in which has a kernel side copy of this
data structure from userspace already.

Fix based upon a suggestion from Alexei Starovoitov.

Signed-off-by: David S. Miller 
Acked-by: Daniel Borkmann