tree 5e84c0c947e50877f9e3ba67a634ea5d838c2d23
parent 265d7657c9baf09d57eb386d0374e912e9649626
author Daniel Borkmann <daniel@iogearbox.net> 1517190541 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1517399757 +0100

bpf: reject stores into ctx via st and xadd

[ upstream commit f37a8cb84cce18762e8f86a70bd6a49a66ab964c ]

Alexei found that verifier does not reject stores into context
via BPF_ST instead of BPF_STX. And while looking at it, we
also should not allow XADD variant of BPF_STX.

The context rewriter is only assuming either BPF_LDX_MEM- or
BPF_STX_MEM-type operations, thus reject anything other than
that so that assumptions in the rewriter properly hold. Add
test cases as well for BPF selftests.

Fixes: d691f9e8d440 ("bpf: allow programs to write to certain skb fields")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>