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Wed, 23 Sep 2026 19:12:01 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Thu, 24 Sep 2026 02:12:01 +0000 Message-Id: From: "Alexei Starovoitov" To: , Cc: , , , , , , , , Subject: Re: [PATCH bpf-next 10/17] bpf: Recognize pointers to functions in read-only maps In-Reply-To: <7f1587113ee73116a351e6a5316e2b8f7485b1cdb69ab60fd56ae9069e98d767@mail.kernel.org> References: <20260922011323.1298619-11-alexei.starovoitov@gmail.com> <7f1587113ee73116a351e6a5316e2b8f7485b1cdb69ab60fd56ae9069e98d767@mail.kernel.org> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, Sep 24, 2026 at 12:46 AM bot+bpf-ci@kernel.org wrote: >> + while (i < cnt && ptrs[i].map_off < o) >> + i++; >> + if (i == cnt || ptrs[i].map_off != o) >> + goto overlap; > > Can reads that don't actually overlap pointers still be rejected here? > Looking at the bounds-based overlap check, when a vtable-like struct has > both data and function pointers (e.g., struct { u64 data; void (*fn)(void); } > with stride 16), reading tbl[i].data gives var_off with offsets 0, 16, 32... > where every tnum-possible offset is non-pointer data. That's a limitation of v1, but sure I'll try to make it work in v2. >> + if (env->func_ptr_cnt) { >> + err = check_func_ptr_read(env, reg, off, size, value_regno); > > Does a PTR_TO_FUNC loaded from a map force the program to be JITed? > check_func_ptr_read() marks the register as PTR_TO_FUNC but doesn't set > env->prog->jit_required. The map still holds the byte offset (e.g. 0x40), > not a real address until jit_subprogs() patches it. Will fix in v2: the read of such pointer will set jit_required.