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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49ce5927b68sm180216205e9.1.2026.09.03.23.37.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Sep 2026 23:37:04 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Ning Ding , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Emil Tsalapatis , Nicholas Carlini , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf v1 8/8] selftests/bpf: Reject refcount acquisition after RCU unlock Date: Fri, 4 Sep 2026 08:36:46 +0200 Message-ID: <20260904063650.3877826-9-memxor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260904063650.3877826-1-memxor@gmail.com> References: <20260904063650.3877826-1-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=1790; i=memxor@gmail.com; h=from:subject; bh=UFxYaQXVBNATr1x5p3orV09A2rwwzpQ5UexFnEal+Eg=; b=owGbwMvMwCXmrmtenRyi38x4Wi2JIWtW2pUWIYaofo7irR3bb/grb9uzNik77+WMRM5tdYoer 2+ujnjfUcrCIMbFICumyFLyfx+T8YnK34G2y7hh5rAygQxh4OIUgInME2H4w3fpA0exy+Uj366X LjKdku7W/Vhv5pVJH3Vn7Y/8sjpl23mGfzbrmqYL3tGYuYyR935O3PEIaRW9ZukzK2Y9njNN6ND aBH4A X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=B34BD741DE8494B76E2F717880EF20021D46C59B Content-Transfer-Encoding: 8bit From: Ning Ding Add a sleepable verifier test that loads a refcount-only local kptr in an explicit RCU read-side critical section, ends the section, and passes the pointer to bpf_refcount_acquire(). The loaded pointer never carries NON_OWN_REF. After RCU unlock it retains MEM_ALLOC while becoming PTR_UNTRUSTED, which previously made the kfunc argument check accept it as a live allocated object. Expect verification to reject the untrusted argument instead. Signed-off-by: Ning Ding [ kkd: Rewrote commit log ] Signed-off-by: Kumar Kartikeya Dwivedi --- .../bpf/progs/refcounted_kptr_fail.c | 27 +++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c index 5abd8387d26f..7be45100c4d6 100644 --- a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c +++ b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c @@ -187,6 +187,33 @@ long rbtree_remove_after_rcu_unlock(void *ctx) return 0; } +SEC("?syscall") +__failure __msg("R1 is neither owning or non-owning ref") +long refcount_acquire_after_rcu_unlock(void *ctx) +{ + struct map_value_refcount_only *mapval; + struct node_refcount_only *node, *ref; + int idx = 0; + + mapval = bpf_map_lookup_elem(&stashed_refcount_only, &idx); + if (!mapval) + return 0; + + bpf_rcu_read_lock(); + node = mapval->node; + if (!node) { + bpf_rcu_read_unlock(); + return 0; + } + bpf_rcu_read_unlock(); + + ref = bpf_refcount_acquire(node); + if (ref) + bpf_obj_drop(ref); + + return 0; +} + SEC("?syscall") __failure __msg("invalid mem access 'scalar'") long graph_kptr_after_spin_unlock(void *ctx) -- 2.53.0