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Sun, 26 Apr 2026 10:25:35 -0700 (PDT) From: Junyoung Jang To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com Cc: martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, greg@kroah.com, security@kernel.org, Junyoung Jang Subject: [PATCH bpf v2] bpf: Fix off-by-one boundary validation in arena direct-value access Date: Mon, 27 Apr 2026 02:25:05 +0900 Message-ID: <20260426172505.1947915-1-graypanda.inzag@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <2026042614-scowling-hankie-f84b@gregkh> References: <2026042614-scowling-hankie-f84b@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit BPF_MAP_TYPE_ARENA accepts BPF_PSEUDO_MAP_VALUE offsets at exactly the end of the arena mapping (off == arena_size). The boundary check in arena_map_direct_value_addr() uses `>` instead of `>=`, which incorrectly allows a one-past-end pointer to be accepted. Change the condition to `>=` to correctly reject offsets that fall outside the valid arena user_vm range. Fixes: 317460317a02 ("bpf: Introduce bpf_arena.") Signed-off-by: Junyoung Jang --- kernel/bpf/arena.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c index 802656c6fd3c..49a8f7b1beef 100644 --- a/kernel/bpf/arena.c +++ b/kernel/bpf/arena.c @@ -511,7 +511,7 @@ static int arena_map_direct_value_addr(const struct bpf_map *map, u64 *imm, u32 { struct bpf_arena *arena = container_of(map, struct bpf_arena, map); - if ((u64)off > arena->user_vm_end - arena->user_vm_start) + if ((u64)off >= arena->user_vm_end - arena->user_vm_start) return -ERANGE; *imm = (unsigned long)arena->user_vm_start; return 0; -- 2.43.0