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Sat, 11 Apr 2026 19:27:30 -0700 (PDT) Received: from efaec68ba852.tailc0aff1.ts.net ([206.206.192.132]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-12c34352490sm8757860c88.0.2026.04.11.19.27.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 11 Apr 2026 19:27:29 -0700 (PDT) From: Weiming Shi To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Barret Rhoden , Emil Tsalapatis , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Xiang Mei , Weiming Shi Subject: [PATCH bpf v4 0/2] bpf: Fix arena VMA use-after-free on fork Date: Sat, 11 Apr 2026 19:27:13 -0700 Message-ID: <20260412022714.1955495-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit arena_vm_open() only increments a refcount on the shared vma_list entry but never registers the new VMA. After fork + parent munmap, vml->vma becomes a dangling pointer. bpf_arena_free_pages -> zap_pages then dereferences it, causing a slab-use-after-free in zap_page_range_single. Patch 1 fixes the bug by tracking each child VMA separately in arena_vm_open, and adds arena_vm_may_split() to prevent VMA splitting. Patch 2 adds a selftest that reproduces the issue (requires KASAN to detect the UAF). v4: - Fixed commit message: OOM case description, may_split rationale v3: - Added arena_vm_may_split() to prevent VMA splitting - Reuse remember_vma() in arena_vm_open(), removed HugeTLB references - selftests: fixed copyright, trimmed comments, use sysconf() v2: - Added missing Reported-by tag Weiming Shi (2): bpf: Fix use-after-free of arena VMA on fork selftests/bpf: Add test for arena VMA use-after-free on fork kernel/bpf/arena.c | 23 ++++-- .../selftests/bpf/prog_tests/arena_fork.c | 80 +++++++++++++++++++ .../testing/selftests/bpf/progs/arena_fork.c | 41 ++++++++++ 3 files changed, 138 insertions(+), 6 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/arena_fork.c create mode 100644 tools/testing/selftests/bpf/progs/arena_fork.c -- 2.43.0