diff mbox series

[bpf-next,2/4] bpf: bpf_fib_lookup should not return neigh in NUD_FAILED state

Message ID 20230217004150.2980689-3-martin.lau@linux.dev (mailing list archive)
State Accepted
Delegated to: BPF
Headers show
Series bpf: A fix and a change to bpf_fib_lookup | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR success PR summary
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 23 this patch: 23
netdev/cc_maintainers warning 11 maintainers not CCed: john.fastabend@gmail.com pabeni@redhat.com sdf@google.com jolsa@kernel.org kuba@kernel.org edumazet@google.com song@kernel.org haoluo@google.com yhs@fb.com kpsingh@kernel.org davem@davemloft.net
netdev/build_clang success Errors and warnings before: 1 this patch: 1
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netdev/verify_signedoff success Signed-off-by tag matches author and committer
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Commit Message

Martin KaFai Lau Feb. 17, 2023, 12:41 a.m. UTC 
From: Martin KaFai Lau <martin.lau@kernel.org>

The bpf_fib_lookup() helper does not only look up the fib (ie. route)
but it also looks up the neigh. Before returning the neigh, the helper
does not check for NUD_VALID. When a neigh state (neigh->nud_state)
is in NUD_FAILED, its dmac (neigh->ha) could be all zeros. The helper
still returns SUCCESS instead of NO_NEIGH in this case. Because of the
SUCCESS return value, the bpf prog directly uses the returned dmac
and ends up filling all zero in the eth header.

This patch checks for NUD_VALID and returns NO_NEIGH if the
neigh is not valid.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
 net/core/filter.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/net/core/filter.c b/net/core/filter.c
index 2ce06a72a5ba..8daaaf76ab15 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5849,7 +5849,7 @@  static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		neigh = __ipv6_neigh_lookup_noref_stub(dev, dst);
 	}
 
-	if (!neigh)
+	if (!neigh || !(neigh->nud_state & NUD_VALID))
 		return BPF_FIB_LKUP_RET_NO_NEIGH;
 
 	return bpf_fib_set_fwd_params(params, neigh, dev, mtu);
@@ -5964,7 +5964,7 @@  static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 	 * not needed here.
 	 */
 	neigh = __ipv6_neigh_lookup_noref_stub(dev, dst);
-	if (!neigh)
+	if (!neigh || !(neigh->nud_state & NUD_VALID))
 		return BPF_FIB_LKUP_RET_NO_NEIGH;
 
 	return bpf_fib_set_fwd_params(params, neigh, dev, mtu);