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Wed, 08 Apr 2026 12:02:12 -0700 (PDT) Received: from computer.goose-salary.ts.net ([2a09:bac5:40b2:1a96::2a6:4e]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35e34d0d9efsm143630a91.8.2026.04.08.12.02.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Apr 2026 12:02:12 -0700 (PDT) From: Varun R Mallya To: bpf@vger.kernel.org, leon.hwang@linux.dev, memxor@gmail.com, jolsa@kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, yonghong.song@linux.dev, rostedt@goodmis.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, varunrmallya@gmail.com Subject: [PATCH bpf-next v5 0/2] Reject sleepable kprobe_multi programs at attach time Date: Thu, 9 Apr 2026 00:31:35 +0530 Message-ID: <20260408190137.101418-1-varunrmallya@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit These patches fix an issue where sleepable kprobe_multi programs were allowed to attach, leading to "sleeping function called from invalid context" splats. Because kprobe.multi programs run in atomic/RCU context, they cannot sleep. However, `bpf_kprobe_multi_link_attach()` previously lacked validation for the `prog->sleepable` flag. This allowed sleepable helpers, such as `bpf_copy_from_user()`, to be invoked from an invalid non-sleepable context. This series addresses the issue by: 1. Rejecting sleepable kprobe_multi programs early in `bpf_kprobe_multi_link_attach()` by returning -EINVAL. 2. Adding selftests to explicitly verify that attaching a sleepable kprobe_multi program is rejected by the kernel. P.S: The first of these two commits has been applied to the bpf tree. Changes: v1->v2: - v1: https://lore.kernel.org/bpf/20260401134921.362148-1-varunrmallya@gmail.com/ - Defective selftest added v2->v3: - v2: https://lore.kernel.org/bpf/CAP01T74YgnKop-dgwBToOcfg4_D44t1wUBopFYPMquirCmaLfg@mail.gmail.com/ - Selftest separated from change into different commit. v3->v4: - v3: https://lore.kernel.org/bpf/20260401191126.440683-1-varunrmallya@gmail.com/ - Selftest moved to test_attach_api_fails. - Changed attachment symbol to bpf_fentry_test1 for stability. - Changes suggested by Leon implemented. v4->v5: - v4: https://lore.kernel.org/bpf/20260408183549.92990-1-varunrmallya@gmail.com/ - fix the mistake of leaving test_attach_multi_sleepable after changing location. Varun R Mallya (2): bpf: Reject sleepable kprobe_multi programs at attach time selftests/bpf: Add test to ensure kprobe_multi is not sleepable kernel/trace/bpf_trace.c | 4 +++ .../bpf/prog_tests/kprobe_multi_test.c | 35 ++++++++++++++++++- .../bpf/progs/kprobe_multi_sleepable.c | 25 +++++++++++++ 3 files changed, 63 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/progs/kprobe_multi_sleepable.c -- 2.53.0