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Tue, 08 Sep 2026 06:53:45 -0700 (PDT) From: Anastasios Papagiannis To: bpf@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, akpm@linux-foundation.org, andrii@kernel.org, ast@kernel.org, brauner@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, kpsingh@kernel.org, ljs@kernel.org, matt@bobrowski.net, memxor@gmail.com, song@kernel.org, sun.jian.kdev@gmail.com, utilityemal77@gmail.com, viro@zeniv.linux.org.uk, tasos.papagiannnis@gmail.com Subject: [PATCH bpf-next v6 4/5] bpf: Mark linux_binprm->mm as trusted-or-null Date: Tue, 8 Sep 2026 16:53:01 +0300 Message-ID: <20260908135302.74963-5-tasos.papagiannnis@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260908135302.74963-1-tasos.papagiannnis@gmail.com> References: <20260908135302.74963-1-tasos.papagiannnis@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Mark linux_binprm->mm as a trusted-or-null nested pointer so BPF programs can pass it to kfuncs after a NULL check. The field is either NULL or points to a live mm_struct whenever BPF can access a linux_binprm. On successful exec, exec_mmap() installs the new address space before begin_new_exec() clears bprm->mm. The bprm_mm_init() error path clears the field before mmdrop(), and free_bprm() clears it before mmput(), as ensured by an earlier patch in this series. Update the existing LSM selftest to check bprm->mm for NULL before dereferencing it, as required for trusted-or-null pointers. Signed-off-by: Anastasios Papagiannis Reviewed-by: Sun Jian Reviewed-By: Matt Bobrowski --- kernel/bpf/verifier.c | 5 +++++ tools/testing/selftests/bpf/progs/lsm.c | 5 ++++- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9e79750e2480..791b3d25caa5 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6004,6 +6004,10 @@ BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct dentry) { struct inode *d_inode; }; +BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct linux_binprm) { + struct mm_struct *mm; +}; + BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket) { struct sock *sk; }; @@ -6058,6 +6062,7 @@ static bool type_is_trusted_or_null(struct bpf_verifier_env *env, { BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket)); BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct dentry)); + BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct linux_binprm)); BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct vm_area_struct)); return btf_nested_type_is_trusted(&env->log, reg, field_name, btf_id, diff --git a/tools/testing/selftests/bpf/progs/lsm.c b/tools/testing/selftests/bpf/progs/lsm.c index 7de173daf27b..7441d66c080c 100644 --- a/tools/testing/selftests/bpf/progs/lsm.c +++ b/tools/testing/selftests/bpf/progs/lsm.c @@ -113,6 +113,7 @@ int BPF_PROG(test_void_hook, struct linux_binprm *bprm) { __u32 pid = bpf_get_current_pid_tgid() >> 32; struct inner_map *inner_map; + struct mm_struct *mm; char args[64]; __u32 key = 0; __u64 *value; @@ -121,7 +122,9 @@ int BPF_PROG(test_void_hook, struct linux_binprm *bprm) bprm_count++; bpf_copy_from_user(args, sizeof(args), (void *)bprm->vma->vm_mm->arg_start); - bpf_copy_from_user(args, sizeof(args), (void *)bprm->mm->arg_start); + mm = bprm->mm; + if (mm) + bpf_copy_from_user(args, sizeof(args), (void *)mm->arg_start); value = bpf_map_lookup_elem(&array, &key); if (value) -- 2.55.0