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Mon, 23 Jun 2025 20:12:58 -0700 (PDT) Received: from localhost ([2a03:2880:30ff:4::]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae0541b74b6sm799063966b.139.2025.06.23.20.12.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Jun 2025 20:12:58 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Eduard Zingerman , Emil Tsalapatis , Barret Rhoden , Matt Bobrowski , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf-next v3 04/12] bpf: Ensure RCU lock is held around bpf_prog_ksym_find Date: Mon, 23 Jun 2025 20:12:44 -0700 Message-ID: <20250624031252.2966759-5-memxor@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250624031252.2966759-1-memxor@gmail.com> References: <20250624031252.2966759-1-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=1390; h=from:subject; bh=bUd0XtTZi2Q1rDeeS93KIgF8ovcFjORZlwjB5QZbIuQ=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBoWhWd4pvZNAKuDmZI5VnDyOVWNq2O0IWMCTGNNnLG lQM4MuCJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCaFoVnQAKCRBM4MiGSL8RyqYVD/ 4/kaM6PXfpJaJbMCyoeWWQ0hybWyjYfVHhEUFo3xSs2815ZWcI5kxCqJrFTKMm7yfHaZhnHlezHq10 ignOpEHCjLfeVuTfepshRkjUyFCOpMtA36HZYDHMtknVMlknpzud4vgnt2WZlHfybFC9kYIars2BgM WIvPNKOgXK/DiKCo8cjqqy6bpfw9AYTP6OvfsWJChChijBTIkFDQCuVjWTqAvPZ+cfFC7HygcY0KBg ngxKtv6JR7LpmURWkyqBFrt64oz7X1XEoq4YalIChhB6E42EeYgDWgZpo5Xe1ZsVhUQ3ebDLycJhO1 Pk7AWHBlsx8tiFcv3K1A4UyHu9vP7s/yex/DjZG6xGCPpd2gMGijtmVvD+ACdwMPfA7o8ERVUkdxbn 5PmAN2P0FzJfKuL+siBBRJnY2AsgD9p9cEspgDsEr96xECKeIMVr6hErd0BTUBeel4T5x5fCaUh/Sb g0FAy+8XZ7RkDyv2YOM0/VxMfVDtSjQo9uAR+x3HR5bRzFDpo+DJypfcspNFtmAxAkeQ/W3dWUNm0t 6qDVLcwHkcYCb6exMNy21mWHiIaG/4Ws6gCaOpcvKNxwnoAPEZtlSIJB7B75X2AWj9z6nM3XGiuCt7 isUTOcHKUwRTSDEx2zSzjl+VhewGi2fMdMLQBcB3c26qX+gp44jc40LET5tQ== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=4BBE2A7E06ECF9D5823C61114CE0C88648BF11CA Content-Transfer-Encoding: 8bit Add a warning to ensure RCU lock is held around tree lookup, and then fix one of the invocations in bpf_stack_walker. The program has an active stack frame and won't disappear. Fixes: f18b03fabaa9 ("bpf: Implement BPF exceptions") Signed-off-by: Kumar Kartikeya Dwivedi --- kernel/bpf/core.c | 5 ++++- kernel/bpf/helpers.c | 2 ++ 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 5c6e9fbb5508..b4203f68cf33 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -782,7 +782,10 @@ bool is_bpf_text_address(unsigned long addr) struct bpf_prog *bpf_prog_ksym_find(unsigned long addr) { - struct bpf_ksym *ksym = bpf_ksym_find(addr); + struct bpf_ksym *ksym; + + WARN_ON_ONCE(!rcu_read_lock_held()); + ksym = bpf_ksym_find(addr); return ksym && ksym->prog ? container_of(ksym, struct bpf_prog_aux, ksym)->prog : diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 8fef7b3cbd80..61b69eb08c4a 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2936,7 +2936,9 @@ static bool bpf_stack_walker(void *cookie, u64 ip, u64 sp, u64 bp) if (!is_bpf_text_address(ip)) return !ctx->cnt; + rcu_read_lock(); prog = bpf_prog_ksym_find(ip); + rcu_read_unlock(); ctx->cnt++; if (bpf_is_subprog(prog)) return true; -- 2.47.1