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[76.146.13.146]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7390618e59esm321135b3a.170.2025.03.20.14.41.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Mar 2025 14:41:07 -0700 (PDT) From: Amery Hung To: bpf@vger.kernel.org Cc: daniel@iogearbox.net, andrii@kernel.org, alexei.starovoitov@gmail.com, martin.lau@kernel.org, ameryhung@gmail.com, kernel-team@meta.com Subject: [RFC PATCH 1/4] bpf: Allow creating dynptr from uptr Date: Thu, 20 Mar 2025 14:40:55 -0700 Message-ID: <20250320214058.2946857-2-ameryhung@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250320214058.2946857-1-ameryhung@gmail.com> References: <20250320214058.2946857-1-ameryhung@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net X-Patchwork-State: RFC Currently, bpf_dynptr_from_mem() only allows creating dynptr from local memory of reg type PTR_TO_MAP_VALUE, specifically ringbuf. This patch futher supports PTR_TO_MEM as a valid source of data. For a reg to be PTR_TO_MEM in the verifier: - read map value with special field BPF_UPTR - ld_imm64 kfunc (MEM_RDONLY) - ld_imm64 other non-struct ksyms (MEM_RDONLY) - return from helper with RET_PTR_TO_MEM: ringbuf_reserve (MEM_RINGBUF) and dynptr_from_data - return from helper with RET_PTR_TO_MEM_OR_BTF_ID: this_cpu_ptr, per_cpu_ptr and the return type is not struct (both MEM_RDONLY) - return from special kfunc: dynptr_slice (MEM_RDONLY), dynptr_slice_rdwr - return from non-special kfunc that returns non-struct pointer: hid_bpf_get_data Since this patch only allows PTR_TO_MEM without any flags, so only uptr, global subprog argument, non-special kfunc that returns non-struct ptr, return of bpf_dynptr_slice_rdwr() and bpf_dynptr_data() will be allowed additionally. The last two will allow creating dynptr from dynptr data. Will they create any problem? Signed-off-by: Amery Hung --- include/uapi/linux/bpf.h | 4 +++- kernel/bpf/verifier.c | 3 ++- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index beac5cdf2d2c..2b1335fa1173 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5562,7 +5562,9 @@ union bpf_attr { * Description * Get a dynptr to local memory *data*. * - * *data* must be a ptr to a map value. + * *data* must be a ptr to valid local memory such as a map value, a uptr, + * a null-checked non-void pointer pass to a global subprogram, and allocated + * memory returned by a kfunc such as hid_bpf_get_data(), * The maximum *size* supported is DYNPTR_MAX_SIZE. * *flags* is currently unused. * Return diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 22c4edc8695c..d22310d1642c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11307,7 +11307,8 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn } break; case BPF_FUNC_dynptr_from_mem: - if (regs[BPF_REG_1].type != PTR_TO_MAP_VALUE) { + if (regs[BPF_REG_1].type != PTR_TO_MAP_VALUE && + regs[BPF_REG_1].type != PTR_TO_MEM) { verbose(env, "Unsupported reg type %s for bpf_dynptr_from_mem data\n", reg_type_str(env, regs[BPF_REG_1].type)); return -EACCES;