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authorDaniel Borkmann <daniel@iogearbox.net>2017-09-20 00:44:21 +0200
committerDavid S. Miller <davem@davemloft.net>2017-09-19 16:38:53 -0700
commit7c30013133964aaa2f45c17d6e9782ac6cfd7f5f (patch)
tree4ce9a1dd192a35dfb8a3ee4b66e37f2c8c9a90d2 /kernel
parentf55956065ec94e3e9371463d693a1029c4cc3007 (diff)
bpf: fix ri->map_owner pointer on bpf_prog_realloc
Commit 109980b894e9 ("bpf: don't select potentially stale ri->map from buggy xdp progs") passed the pointer to the prog itself to be loaded into r4 prior on bpf_redirect_map() helper call, so that we can store the owner into ri->map_owner out of the helper. Issue with that is that the actual address of the prog is still subject to change when subsequent rewrites occur that require slow path in bpf_prog_realloc() to alloc more memory, e.g. from patching inlining helper functions or constant blinding. Thus, we really need to take prog->aux as the address we're holding, which also works with prog clones as they share the same aux object. Instead of then fetching aux->prog during runtime, which could potentially incur cache misses due to false sharing, we are going to just use aux for comparison on the map owner. This will also keep the patchlet of the same size, and later check in xdp_map_invalid() only accesses read-only aux pointer from the prog, it's also in the same cacheline already from prior access when calling bpf_func. Fixes: 109980b894e9 ("bpf: don't select potentially stale ri->map from buggy xdp progs") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 799b2451ef2d..b914fbe1383e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4205,7 +4205,12 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
}
if (insn->imm == BPF_FUNC_redirect_map) {
- u64 addr = (unsigned long)prog;
+ /* Note, we cannot use prog directly as imm as subsequent
+ * rewrites would still change the prog pointer. The only
+ * stable address we can use is aux, which also works with
+ * prog clones during blinding.
+ */
+ u64 addr = (unsigned long)prog->aux;
struct bpf_insn r4_ld[] = {
BPF_LD_IMM64(BPF_REG_4, addr),
*insn,