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Sat, 10 Oct 2026 14:02:59 -0700 (PDT) Received: from mbili.waya ([64.203.83.2]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93eb984845csm498538085a.14.2026.10.10.14.02.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 Oct 2026 14:02:58 -0700 (PDT) From: Jamal Hadi Salim To: netdev@vger.kernel.org Cc: Jamal Hadi Salim , kuba@kernel.org, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@kernel.org, pabeni@redhat.com, sdf@fomichev.me, martin.lau@kernel.org, daniel@iogearbox.net, horms@kernel.org, qmo@kernel.org, bpf@vger.kernel.org, jiri@resnulli.us, stable@vger.kernel.org, sashiko-bot@kernel.org, victor@mojatatu.com Subject: [PATCH net v2 1/3] netdevsim: reject cls_bpf programs bound to another device Date: Sat, 10 Oct 2026 17:02:48 -0400 Message-Id: X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The issue: nsim_bpf_setup_tc_block_cb() installs any device-bound SCHED_CLS program without checking that its offload device matches the target netdev. The core cls_bpf attach path rejects a mismatching program, but a netdev that joins a shared block later is replayed the stored filter by cls_bpf_reoffload() before it is inserted into block->ports, so the attach-time check cannot see it. The driver callback is the authoritative per-device acceptance boundary and must enforce the match itself, as nfp already does in nfp_net_bpf_offload(). Without the check, replaying a device-bound program onto a different bpf_offload_dev installs it into that device's netdevsim state, which trips the WARN in nsim_bpf_uninit() (ns->bpf_offloaded set on a foreign device) and can dereference a NULL prog->aux->offload in nsim_prog_set_loaded(). The Fix: Reject a device-bound program whose offload device does not match the target netdev, with -EINVAL and an extack so the rejected replay is not silent. The check is intentionally narrower than nfp's: it fires only for a dev-bound program, so nsim's bpf_tc_non_bound_accept mode (which admits an unbound program onto the device) is unaffected. Teardown is never blocked: the guard is on the program being installed and an unbind passes cls_bpf.prog = NULL. Conditions to recreate the bug: - CONFIG_NETDEVSIM=y, CONFIG_NET_CLS_BPF=y - load and pin a dev-bound SCHED_CLS program for netdevsim device B - install the program on a shared block owned by B - add an independently backed netdevsim device C to that block; the bind replays the filter to C's callback, and C's ports/0/bpf_offloaded_id takes the B-bound program id. The reported Sashiko review is at https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260809094418.901607-1-jhs@mojatatu.com Fixes: 31d3ad832948 ("netdevsim: add bpf offload support") Reported-by: Sashiko (nipa) Link: https://lore.kernel.org/netdev/20260809094418.901607-1-jhs@mojatatu.com/ Link: https://lore.kernel.org/netdev/QDISC-PYC7.v1.20261003103747@mojatatu.com/ Cc: stable@vger.kernel.org Reviewed-by: Victor Nogueira Signed-off-by: Jamal Hadi Salim --- v1 -> v2 (v2 of an on-list patch; v1 posted 2026-10-04): - Finding (nipa Sashiko High, v1) -- FIXED: the every-member predicate is enforced only at add/replace, but a netdev joining a shared block later is replayed the stored filter by cls_bpf_reoffload() before it is inserted into block->ports (tcf_block_offload_bind precedes the xa_insert). Neither cls_bpf_reoffload() nor nsim_bpf_setup_tc_block_cb() checked bpf_offload_dev_match(), so the B-bound program was installed on the joining device (re-opening the 120977e2c096 mixed-block defect). Fixed by enforcing the device match in nsim_bpf_setup_tc_block_cb() (drivers/net/netdevsim/bpf.c), mirroring nfp. - Style (gemini + nipa Low) -- FIXED: the shared-block comment opens with /* on its own line. - The companion selftest exercises shared-block and late-join coverage, pinning both the all-members predicate and this callback's replay gate. - Split the single v2 draft into [PATCH net v2 1/3] netdevsim, 2/3 cls_bpf and 3/3 selftests, each with its own Fixes: and stable metadata. --- drivers/net/netdevsim/bpf.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/net/netdevsim/bpf.c b/drivers/net/netdevsim/bpf.c index 16aa88278398..a73ea8b07682 100644 --- a/drivers/net/netdevsim/bpf.c +++ b/drivers/net/netdevsim/bpf.c @@ -144,6 +144,18 @@ int nsim_bpf_setup_tc_block_cb(enum tc_setup_type type, return -EOPNOTSUPP; } + /* + * A dev-bound program can be replayed here when a netdev joins a + * shared block, after the core attach-time check has run; enforce + * the device match as nfp does. + */ + if (prog && bpf_prog_is_dev_bound(prog->aux) && + !bpf_offload_dev_match(prog, ns->netdev)) { + NSIM_EA(cls_bpf->common.extack, + "program bound to a different device"); + return -EINVAL; + } + if (cls_bpf->command != TC_CLSBPF_OFFLOAD) return -EOPNOTSUPP; -- 2.43.0