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Wed, 13 Dec 2023 22:28:37 -0800 (PST) From: Menglong Dong To: andrii@kernel.org, eddyz87@gmail.com, yonghong.song@linux.dev Cc: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, martin.lau@linux.dev, song@kernel.org, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Menglong Dong Subject: [PATCH bpf-next v3 0/2] bpf: support to track BPF_JNE Date: Thu, 14 Dec 2023 14:24:32 +0800 Message-Id: <20231214062434.3565630-1-menglong8.dong@gmail.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Wed, 13 Dec 2023 22:28:42 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1785237680880567774 X-GMAIL-MSGID: 1785237680880567774 For now, the reg bounds is not handled for BPF_JNE case, which can cause the failure of following case: /* The type of "a" is u16 */ if (a > 0 && a < 100) { /* the range of the register for a is [0, 99], not [1, 99], * and will cause the following error: * * invalid zero-sized read * * as a can be 0. */ bpf_skb_store_bytes(skb, xx, xx, a, 0); } In the code above, "a > 0" will be compiled to "jmp xxx if a == 0". In the TRUE branch, the dst_reg will be marked as known to 0. However, in the fallthrough(FALSE) branch, the dst_reg will not be handled, which makes the [min, max] for a is [0, 99], not [1, 99]. In the 1st patch, we reduce the range of the dst reg if the src reg is a const and is exactly the edge of the dst reg For BPF_JNE. In the 2nd patch, we just activate the test case for this logic in range_cond(), which is committed by Andrii in the commit 8863238993e2 ("selftests/bpf: BPF register range bounds tester"). Changes since v2: - fix a typo in the subject of the 1st patch - add some comments to the 1st patch, as Eduard advised - add some cases to the "crafted_cases" Changes since v1: - simplify the code in the 1st patch - introduce the 2nd patch for the testing Menglong Dong (2): bpf: make the verifier tracks the "not equal" for regs selftests/bpf: activate the OP_NE login in range_cond() kernel/bpf/verifier.c | 38 ++++++++++++++++++- .../selftests/bpf/prog_tests/reg_bounds.c | 25 +++++++++--- 2 files changed, 56 insertions(+), 7 deletions(-)