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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4887a84205esm13920686f8f.37.2026.09.26.06.30.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Sep 2026 06:30:50 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Emil Tsalapatis , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf-next v4 1/3] selftests/bpf: Test non-sleepable kfunc context Date: Sat, 26 Sep 2026 15:30:43 +0200 Message-ID: <20260926133048.2962553-2-memxor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260926133048.2962553-1-memxor@gmail.com> References: <20260926133048.2962553-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2318; i=memxor@gmail.com; h=from:subject; bh=7BVB89PKLVO6i5G2jI7rGPJfLWFoJWGU1PnXo22Lcv0=; b=owGbwMvMwCXmrmtenRyi38x4Wi2JIWv7iSfbBfYFHNp7q0SNO7z6scDMmg+XliW95Di/8wFPt aWkftKJjlIWBjEuBlkxRZaS//uYjE9U/g60XcYNM4eVCWQIAxenAEzE7SXDHy4mc2bpPVVT/3Rc myr+3evVVJH3p7T+ZU7kmH4g5d8u10BGhjsTpyiuWPTHxto1JSrol/WCflvTrT2/XkjGeFtrzb+ xlgUA X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=B34BD741DE8494B76E2F717880EF20021D46C59B Content-Transfer-Encoding: 8bit A sleepable kfunc call can be rejected because the program itself is not sleepable or because a sleepable program is inside an active critical section. Exercise the two causes separately. Call a sleepable kfunc directly from a non-sleepable tracing program, then call it from a sleepable tracing program inside an RCU read-side critical section. Assert both the legacy verifier messages and the structured reasons. Link: https://lore.kernel.org/bpf/2e42a1a2bf45f4d2aba7495bdc9f147558055740e2f3c8b9dae255f6c57fc13c@mail.kernel.org/ Link: https://lore.kernel.org/r/20260924170646.2366016-6-memxor@gmail.com Signed-off-by: Kumar Kartikeya Dwivedi --- .../selftests/bpf/progs/preempt_lock.c | 26 +++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/preempt_lock.c b/tools/testing/selftests/bpf/progs/preempt_lock.c index 81c459435680..955391da326a 100644 --- a/tools/testing/selftests/bpf/progs/preempt_lock.c +++ b/tools/testing/selftests/bpf/progs/preempt_lock.c @@ -6,6 +6,8 @@ #include "bpf_experimental.h" extern int bpf_copy_from_user_str(void *dst, u32 dst__sz, const void *unsafe_ptr__ign, u64 flags) __weak __ksym; +extern void bpf_rcu_read_lock(void) __ksym; +extern void bpf_rcu_read_unlock(void) __ksym; SEC("?tc") __failure __msg("BPF_EXIT instruction in main prog cannot be used inside bpf_preempt_disable-ed region") @@ -179,6 +181,30 @@ int preempt_sleepable_kfunc(void *ctx) return 0; } +SEC("?fentry/" SYS_PREFIX "sys_getpgid") +__failure __msg("program must be sleepable to call sleepable kfunc bpf_copy_from_user_str") +__msg("cannot be used in non-sleepable program") +int non_sleepable_kfunc(void *ctx) +{ + u32 data; + + bpf_copy_from_user_str(&data, sizeof(data), NULL, 0); + return 0; +} + +SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") +__failure __msg("kernel func bpf_copy_from_user_str is sleepable within rcu_read_lock region") +__msg("cannot be used in RCU read lock region") +int sleepable_kfunc_in_rcu(void *ctx) +{ + u32 data; + + bpf_rcu_read_lock(); + bpf_copy_from_user_str(&data, sizeof(data), NULL, 0); + bpf_rcu_read_unlock(); + return 0; +} + int __noinline preempt_global_subprog(void) { preempt_balance_subprog(); -- 2.53.0