<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/samples/bpf, branch v4.9.20</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>bpf/samples: Fix PT_REGS_IP on s390x and use it</title>
<updated>2016-11-28T21:26:46+00:00</updated>
<author>
<name>Michael Holzheu</name>
<email>holzheu@linux.vnet.ibm.com</email>
</author>
<published>2016-11-28T12:48:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=2dbb4c05d048995455857a7c2927a4297fc66c3b'/>
<id>2dbb4c05d048995455857a7c2927a4297fc66c3b</id>
<content type='text'>
The files "sampleip_kern.c" and "trace_event_kern.c" directly access
"ctx-&gt;regs.ip" which is not available on s390x. Fix this and use the
PT_REGS_IP() macro instead.

Also fix the macro for s390x and use "psw.addr" from "pt_regs".

Reported-by: Zvonko Kosic &lt;zvonko.kosic@de.ibm.com&gt;
Signed-off-by: Michael Holzheu &lt;holzheu@linux.vnet.ibm.com&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The files "sampleip_kern.c" and "trace_event_kern.c" directly access
"ctx-&gt;regs.ip" which is not available on s390x. Fix this and use the
PT_REGS_IP() macro instead.

Also fix the macro for s390x and use "psw.addr" from "pt_regs".

Reported-by: Zvonko Kosic &lt;zvonko.kosic@de.ibm.com&gt;
Signed-off-by: Michael Holzheu &lt;holzheu@linux.vnet.ibm.com&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpf: Add test for bpf_redirect to ipip/ip6tnl</title>
<updated>2016-11-13T04:38:07+00:00</updated>
<author>
<name>Martin KaFai Lau</name>
<email>kafai@fb.com</email>
</author>
<published>2016-11-09T23:36:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=90e02896f1a4627b14624245fbcbc19f8fd916cb'/>
<id>90e02896f1a4627b14624245fbcbc19f8fd916cb</id>
<content type='text'>
The test creates two netns, ns1 and ns2.  The host (the default netns)
has an ipip or ip6tnl dev configured for tunneling traffic to the ns2.

    ping VIPS from ns1 &lt;----&gt; host &lt;--tunnel--&gt; ns2 (VIPs at loopback)

The test is to have ns1 pinging VIPs configured at the loopback
interface in ns2.

The VIPs are 10.10.1.102 and 2401:face::66 (which are configured
at lo@ns2). [Note: 0x66 =&gt; 102].

At ns1, the VIPs are routed _via_ the host.

At the host, bpf programs are installed at the veth to redirect packets
from a veth to the ipip/ip6tnl.  The test is configured in a way so
that both ingress and egress can be tested.

At ns2, the ipip/ip6tnl dev is configured with the local and remote address
specified.  The return path is routed to the dev ipip/ip6tnl.

During egress test, the host also locally tests pinging the VIPs to ensure
that bpf_redirect at egress also works for the direct egress (i.e. not
forwarding from dev ve1 to ve2).

Acked-by: Alexei Starovoitov &lt;ast@fb.com&gt;
Signed-off-by: Martin KaFai Lau &lt;kafai@fb.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The test creates two netns, ns1 and ns2.  The host (the default netns)
has an ipip or ip6tnl dev configured for tunneling traffic to the ns2.

    ping VIPS from ns1 &lt;----&gt; host &lt;--tunnel--&gt; ns2 (VIPs at loopback)

The test is to have ns1 pinging VIPs configured at the loopback
interface in ns2.

The VIPs are 10.10.1.102 and 2401:face::66 (which are configured
at lo@ns2). [Note: 0x66 =&gt; 102].

At ns1, the VIPs are routed _via_ the host.

At the host, bpf programs are installed at the veth to redirect packets
from a veth to the ipip/ip6tnl.  The test is configured in a way so
that both ingress and egress can be tested.

At ns2, the ipip/ip6tnl dev is configured with the local and remote address
specified.  The return path is routed to the dev ipip/ip6tnl.

During egress test, the host also locally tests pinging the VIPs to ensure
that bpf_redirect at egress also works for the direct egress (i.e. not
forwarding from dev ve1 to ve2).

Acked-by: Alexei Starovoitov &lt;ast@fb.com&gt;
Signed-off-by: Martin KaFai Lau &lt;kafai@fb.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpf: fix samples to add fake KBUILD_MODNAME</title>
<updated>2016-10-29T18:46:12+00:00</updated>
<author>
<name>Daniel Borkmann</name>
<email>daniel@iogearbox.net</email>
</author>
<published>2016-10-25T22:37:53+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=96a8eb1eeed2c3485cdba198fab3a2faaec386d3'/>
<id>96a8eb1eeed2c3485cdba198fab3a2faaec386d3</id>
<content type='text'>
Some of the sample files are causing issues when they are loaded with tc
and cls_bpf, meaning tc bails out while trying to parse the resulting ELF
file as program/map/etc sections are not present, which can be easily
spotted with readelf(1).

Currently, BPF samples are including some of the kernel headers and mid
term we should change them to refrain from this, really. When dynamic
debugging is enabled, we bail out due to undeclared KBUILD_MODNAME, which
is easily overlooked in the build as clang spills this along with other
noisy warnings from various header includes, and llc still generates an
ELF file with mentioned characteristics. For just playing around with BPF
examples, this can be a bit of a hurdle to take.

Just add a fake KBUILD_MODNAME as a band-aid to fix the issue, same is
done in xdp*_kern samples already.

Fixes: 65d472fb007d ("samples/bpf: add 'pointer to packet' tests")
Fixes: 6afb1e28b859 ("samples/bpf: Add tunnel set/get tests.")
Fixes: a3f74617340b ("cgroup: bpf: Add an example to do cgroup checking in BPF")
Reported-by: Chandrasekar Kannan &lt;ckannan@console.to&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Some of the sample files are causing issues when they are loaded with tc
and cls_bpf, meaning tc bails out while trying to parse the resulting ELF
file as program/map/etc sections are not present, which can be easily
spotted with readelf(1).

Currently, BPF samples are including some of the kernel headers and mid
term we should change them to refrain from this, really. When dynamic
debugging is enabled, we bail out due to undeclared KBUILD_MODNAME, which
is easily overlooked in the build as clang spills this along with other
noisy warnings from various header includes, and llc still generates an
ELF file with mentioned characteristics. For just playing around with BPF
examples, this can be a bit of a hurdle to take.

Just add a fake KBUILD_MODNAME as a band-aid to fix the issue, same is
done in xdp*_kern samples already.

Fixes: 65d472fb007d ("samples/bpf: add 'pointer to packet' tests")
Fixes: 6afb1e28b859 ("samples/bpf: Add tunnel set/get tests.")
Fixes: a3f74617340b ("cgroup: bpf: Add an example to do cgroup checking in BPF")
Reported-by: Chandrasekar Kannan &lt;ckannan@console.to&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpf: allow access into map value arrays</title>
<updated>2016-09-29T05:35:35+00:00</updated>
<author>
<name>Josef Bacik</name>
<email>jbacik@fb.com</email>
</author>
<published>2016-09-28T14:54:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=484611357c19f9e19ef742ebef4505a07d243cc9'/>
<id>484611357c19f9e19ef742ebef4505a07d243cc9</id>
<content type='text'>
Suppose you have a map array value that is something like this

struct foo {
	unsigned iter;
	int array[SOME_CONSTANT];
};

You can easily insert this into an array, but you cannot modify the contents of
foo-&gt;array[] after the fact.  This is because we have no way to verify we won't
go off the end of the array at verification time.  This patch provides a start
for this work.  We accomplish this by keeping track of a minimum and maximum
value a register could be while we're checking the code.  Then at the time we
try to do an access into a MAP_VALUE we verify that the maximum offset into that
region is a valid access into that memory region.  So in practice, code such as
this

unsigned index = 0;

if (foo-&gt;iter &gt;= SOME_CONSTANT)
	foo-&gt;iter = index;
else
	index = foo-&gt;iter++;
foo-&gt;array[index] = bar;

would be allowed, as we can verify that index will always be between 0 and
SOME_CONSTANT-1.  If you wish to use signed values you'll have to have an extra
check to make sure the index isn't less than 0, or do something like index %=
SOME_CONSTANT.

Signed-off-by: Josef Bacik &lt;jbacik@fb.com&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Suppose you have a map array value that is something like this

struct foo {
	unsigned iter;
	int array[SOME_CONSTANT];
};

You can easily insert this into an array, but you cannot modify the contents of
foo-&gt;array[] after the fact.  This is because we have no way to verify we won't
go off the end of the array at verification time.  This patch provides a start
for this work.  We accomplish this by keeping track of a minimum and maximum
value a register could be while we're checking the code.  Then at the time we
try to do an access into a MAP_VALUE we verify that the maximum offset into that
region is a valid access into that memory region.  So in practice, code such as
this

unsigned index = 0;

if (foo-&gt;iter &gt;= SOME_CONSTANT)
	foo-&gt;iter = index;
else
	index = foo-&gt;iter++;
foo-&gt;array[index] = bar;

would be allowed, as we can verify that index will always be between 0 and
SOME_CONSTANT-1.  If you wish to use signed values you'll have to have an extra
check to make sure the index isn't less than 0, or do something like index %=
SOME_CONSTANT.

Signed-off-by: Josef Bacik &lt;jbacik@fb.com&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpf samples: update tracex5 sample to use __seccomp_filter</title>
<updated>2016-09-27T07:48:58+00:00</updated>
<author>
<name>Naveen N. Rao</name>
<email>naveen.n.rao@linux.vnet.ibm.com</email>
</author>
<published>2016-09-23T20:40:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=973d94d8a87c32661f1308a118074972ac5d483a'/>
<id>973d94d8a87c32661f1308a118074972ac5d483a</id>
<content type='text'>
seccomp_phase1() does not exist anymore. Instead, update sample to use
__seccomp_filter(). While at it, set max locked memory to unlimited.

Signed-off-by: Naveen N. Rao &lt;naveen.n.rao@linux.vnet.ibm.com&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
seccomp_phase1() does not exist anymore. Instead, update sample to use
__seccomp_filter(). While at it, set max locked memory to unlimited.

Signed-off-by: Naveen N. Rao &lt;naveen.n.rao@linux.vnet.ibm.com&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpf samples: fix compiler errors with sockex2 and sockex3</title>
<updated>2016-09-27T07:48:58+00:00</updated>
<author>
<name>Naveen N. Rao</name>
<email>naveen.n.rao@linux.vnet.ibm.com</email>
</author>
<published>2016-09-23T20:40:04+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=2b064fff8527a1052c7060c65c22cae80a9343b9'/>
<id>2b064fff8527a1052c7060c65c22cae80a9343b9</id>
<content type='text'>
These samples fail to compile as 'struct flow_keys' conflicts with
definition in net/flow_dissector.h. Fix the same by renaming the
structure used in the sample.

Signed-off-by: Naveen N. Rao &lt;naveen.n.rao@linux.vnet.ibm.com&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
These samples fail to compile as 'struct flow_keys' conflicts with
definition in net/flow_dissector.h. Fix the same by renaming the
structure used in the sample.

Signed-off-by: Naveen N. Rao &lt;naveen.n.rao@linux.vnet.ibm.com&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpf: add test cases for direct packet access</title>
<updated>2016-09-21T03:32:11+00:00</updated>
<author>
<name>Daniel Borkmann</name>
<email>daniel@iogearbox.net</email>
</author>
<published>2016-09-19T22:26:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=7d95b0ab5bbe2dc9bf3fd99c27e80ced5bfa8acf'/>
<id>7d95b0ab5bbe2dc9bf3fd99c27e80ced5bfa8acf</id>
<content type='text'>
Add couple of test cases for direct write and the negative size issue, and
also adjust the direct packet access test4 since it asserts that writes are
not possible, but since we've just added support for writes, we need to
invert the verdict to ACCEPT, of course. Summary: 133 PASSED, 0 FAILED.

Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Add couple of test cases for direct write and the negative size issue, and
also adjust the direct packet access test4 since it asserts that writes are
not possible, but since we've just added support for writes, we need to
invert the verdict to ACCEPT, of course. Summary: 133 PASSED, 0 FAILED.

Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>samples/bpf: add comprehensive ipip, ipip6, ip6ip6 test</title>
<updated>2016-09-17T14:13:07+00:00</updated>
<author>
<name>Alexei Starovoitov</name>
<email>ast@fb.com</email>
</author>
<published>2016-09-15T20:00:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=173ca26e9b5136faa82dee37c77cbfb36974d079'/>
<id>173ca26e9b5136faa82dee37c77cbfb36974d079</id>
<content type='text'>
the test creates 3 namespaces with veth connected via bridge.
First two namespaces simulate two different hosts with the same
IPv4 and IPv6 addresses configured on the tunnel interface and they
communicate with outside world via standard tunnels.
Third namespace creates collect_md tunnel that is driven by BPF
program which selects different remote host (either first or
second namespace) based on tcp dest port number while tcp dst
ip is the same.
This scenario is rough approximation of load balancer use case.
The tests check both traditional tunnel configuration and collect_md mode.

Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
the test creates 3 namespaces with veth connected via bridge.
First two namespaces simulate two different hosts with the same
IPv4 and IPv6 addresses configured on the tunnel interface and they
communicate with outside world via standard tunnels.
Third namespace creates collect_md tunnel that is driven by BPF
program which selects different remote host (either first or
second namespace) based on tcp dest port number while tcp dst
ip is the same.
This scenario is rough approximation of load balancer use case.
The tests check both traditional tunnel configuration and collect_md mode.

Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>samples/bpf: extend test_tunnel_bpf.sh with IPIP test</title>
<updated>2016-09-17T14:13:07+00:00</updated>
<author>
<name>Alexei Starovoitov</name>
<email>ast@fb.com</email>
</author>
<published>2016-09-15T20:00:31+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=a1c82704d13fd0d0ab0eb10d33a9bb7af83c90e3'/>
<id>a1c82704d13fd0d0ab0eb10d33a9bb7af83c90e3</id>
<content type='text'>
extend existing tests for vxlan, geneve, gre to include IPIP tunnel.
It tests both traditional tunnel configuration and
dynamic via bpf helpers.

Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
extend existing tests for vxlan, geneve, gre to include IPIP tunnel.
It tests both traditional tunnel configuration and
dynamic via bpf helpers.

Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpf: fix range propagation on direct packet access</title>
<updated>2016-09-09T00:28:37+00:00</updated>
<author>
<name>Daniel Borkmann</name>
<email>daniel@iogearbox.net</email>
</author>
<published>2016-09-07T23:03:42+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=2d2be8cab26ed918e94d2deae89580003242a123'/>
<id>2d2be8cab26ed918e94d2deae89580003242a123</id>
<content type='text'>
LLVM can generate code that tests for direct packet access via
skb-&gt;data/data_end in a way that currently gets rejected by the
verifier, example:

  [...]
   7: (61) r3 = *(u32 *)(r6 +80)
   8: (61) r9 = *(u32 *)(r6 +76)
   9: (bf) r2 = r9
  10: (07) r2 += 54
  11: (3d) if r3 &gt;= r2 goto pc+12
   R1=inv R2=pkt(id=0,off=54,r=0) R3=pkt_end R4=inv R6=ctx
   R9=pkt(id=0,off=0,r=0) R10=fp
  12: (18) r4 = 0xffffff7a
  14: (05) goto pc+430
  [...]

  from 11 to 24: R1=inv R2=pkt(id=0,off=54,r=0) R3=pkt_end R4=inv
                 R6=ctx R9=pkt(id=0,off=0,r=0) R10=fp
  24: (7b) *(u64 *)(r10 -40) = r1
  25: (b7) r1 = 0
  26: (63) *(u32 *)(r6 +56) = r1
  27: (b7) r2 = 40
  28: (71) r8 = *(u8 *)(r9 +20)
  invalid access to packet, off=20 size=1, R9(id=0,off=0,r=0)

The reason why this gets rejected despite a proper test is that we
currently call find_good_pkt_pointers() only in case where we detect
tests like rX &gt; pkt_end, where rX is of type pkt(id=Y,off=Z,r=0) and
derived, for example, from a register of type pkt(id=Y,off=0,r=0)
pointing to skb-&gt;data. find_good_pkt_pointers() then fills the range
in the current branch to pkt(id=Y,off=0,r=Z) on success.

For above case, we need to extend that to recognize pkt_end &gt;= rX
pattern and mark the other branch that is taken on success with the
appropriate pkt(id=Y,off=0,r=Z) type via find_good_pkt_pointers().
Since eBPF operates on BPF_JGT (&gt;) and BPF_JGE (&gt;=), these are the
only two practical options to test for from what LLVM could have
generated, since there's no such thing as BPF_JLT (&lt;) or BPF_JLE (&lt;=)
that we would need to take into account as well.

After the fix:

  [...]
   7: (61) r3 = *(u32 *)(r6 +80)
   8: (61) r9 = *(u32 *)(r6 +76)
   9: (bf) r2 = r9
  10: (07) r2 += 54
  11: (3d) if r3 &gt;= r2 goto pc+12
   R1=inv R2=pkt(id=0,off=54,r=0) R3=pkt_end R4=inv R6=ctx
   R9=pkt(id=0,off=0,r=0) R10=fp
  12: (18) r4 = 0xffffff7a
  14: (05) goto pc+430
  [...]

  from 11 to 24: R1=inv R2=pkt(id=0,off=54,r=54) R3=pkt_end R4=inv
                 R6=ctx R9=pkt(id=0,off=0,r=54) R10=fp
  24: (7b) *(u64 *)(r10 -40) = r1
  25: (b7) r1 = 0
  26: (63) *(u32 *)(r6 +56) = r1
  27: (b7) r2 = 40
  28: (71) r8 = *(u8 *)(r9 +20)
  29: (bf) r1 = r8
  30: (25) if r8 &gt; 0x3c goto pc+47
   R1=inv56 R2=imm40 R3=pkt_end R4=inv R6=ctx R8=inv56
   R9=pkt(id=0,off=0,r=54) R10=fp
  31: (b7) r1 = 1
  [...]

Verifier test cases are also added in this work, one that demonstrates
the mentioned example here and one that tries a bad packet access for
the current/fall-through branch (the one with types pkt(id=X,off=Y,r=0),
pkt(id=X,off=0,r=0)), then a case with good and bad accesses, and two
with both test variants (&gt;, &gt;=).

Fixes: 969bf05eb3ce ("bpf: direct packet access")
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
LLVM can generate code that tests for direct packet access via
skb-&gt;data/data_end in a way that currently gets rejected by the
verifier, example:

  [...]
   7: (61) r3 = *(u32 *)(r6 +80)
   8: (61) r9 = *(u32 *)(r6 +76)
   9: (bf) r2 = r9
  10: (07) r2 += 54
  11: (3d) if r3 &gt;= r2 goto pc+12
   R1=inv R2=pkt(id=0,off=54,r=0) R3=pkt_end R4=inv R6=ctx
   R9=pkt(id=0,off=0,r=0) R10=fp
  12: (18) r4 = 0xffffff7a
  14: (05) goto pc+430
  [...]

  from 11 to 24: R1=inv R2=pkt(id=0,off=54,r=0) R3=pkt_end R4=inv
                 R6=ctx R9=pkt(id=0,off=0,r=0) R10=fp
  24: (7b) *(u64 *)(r10 -40) = r1
  25: (b7) r1 = 0
  26: (63) *(u32 *)(r6 +56) = r1
  27: (b7) r2 = 40
  28: (71) r8 = *(u8 *)(r9 +20)
  invalid access to packet, off=20 size=1, R9(id=0,off=0,r=0)

The reason why this gets rejected despite a proper test is that we
currently call find_good_pkt_pointers() only in case where we detect
tests like rX &gt; pkt_end, where rX is of type pkt(id=Y,off=Z,r=0) and
derived, for example, from a register of type pkt(id=Y,off=0,r=0)
pointing to skb-&gt;data. find_good_pkt_pointers() then fills the range
in the current branch to pkt(id=Y,off=0,r=Z) on success.

For above case, we need to extend that to recognize pkt_end &gt;= rX
pattern and mark the other branch that is taken on success with the
appropriate pkt(id=Y,off=0,r=Z) type via find_good_pkt_pointers().
Since eBPF operates on BPF_JGT (&gt;) and BPF_JGE (&gt;=), these are the
only two practical options to test for from what LLVM could have
generated, since there's no such thing as BPF_JLT (&lt;) or BPF_JLE (&lt;=)
that we would need to take into account as well.

After the fix:

  [...]
   7: (61) r3 = *(u32 *)(r6 +80)
   8: (61) r9 = *(u32 *)(r6 +76)
   9: (bf) r2 = r9
  10: (07) r2 += 54
  11: (3d) if r3 &gt;= r2 goto pc+12
   R1=inv R2=pkt(id=0,off=54,r=0) R3=pkt_end R4=inv R6=ctx
   R9=pkt(id=0,off=0,r=0) R10=fp
  12: (18) r4 = 0xffffff7a
  14: (05) goto pc+430
  [...]

  from 11 to 24: R1=inv R2=pkt(id=0,off=54,r=54) R3=pkt_end R4=inv
                 R6=ctx R9=pkt(id=0,off=0,r=54) R10=fp
  24: (7b) *(u64 *)(r10 -40) = r1
  25: (b7) r1 = 0
  26: (63) *(u32 *)(r6 +56) = r1
  27: (b7) r2 = 40
  28: (71) r8 = *(u8 *)(r9 +20)
  29: (bf) r1 = r8
  30: (25) if r8 &gt; 0x3c goto pc+47
   R1=inv56 R2=imm40 R3=pkt_end R4=inv R6=ctx R8=inv56
   R9=pkt(id=0,off=0,r=54) R10=fp
  31: (b7) r1 = 1
  [...]

Verifier test cases are also added in this work, one that demonstrates
the mentioned example here and one that tries a bad packet access for
the current/fall-through branch (the one with types pkt(id=X,off=Y,r=0),
pkt(id=X,off=0,r=0)), then a case with good and bad accesses, and two
with both test variants (&gt;, &gt;=).

Fixes: 969bf05eb3ce ("bpf: direct packet access")
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
</feed>
