From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7AFF451616F; Wed, 30 Sep 2026 18:43:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790793839; cv=none; b=Asy0tnBILBnxDAVfSOqDalrAqZqgpNcwSiHZc26bFObdCg1u2CtpCZAXhHnGShwMGqWIBe9irgyyoVjyGZFg+zigC78dar0DPFGSAGqioGPzqzNePzpsmQDXQQ8ss2mvYCQTKRGPTdnouNwIjjQYy7oc+MWlIqOl7IaEWgweA28= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790793839; c=relaxed/simple; bh=Qj9TdM+RMOyPEaMPAnI0+SNhmj1K9+0chvHxSH18VAQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Qf9EngfRPNkARMoto+9RXyRT2O8zHdig2ZbiGgFniAmsm3pDBwB6oYWvpGtvFWlCB1e5lgNHSQrSl+a0sTQ13T+l/+kUmUrijfpMKc4vCzuxV+uVf3TqKcEgBT7TcKy0jl7mhtEh922eW8v2vlnH4iCY/1eofNXP31diZt8CGWI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=H++UFK7Y; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="H++UFK7Y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4A441F000FF; Wed, 30 Sep 2026 18:43:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790793838; bh=DiulsmjJuGs/dE89ID00hVvWFsFc5ov4BSapD2nerJo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=H++UFK7YkT5p2Sl61CV7i3ofC4c0XWQM/SoiyKsmVAgeawYsPlIDGSmagCdE+ulXl fNg8ew/V1lkfUjL/qhznyLzGRPr+QGEIn/37qwF5jAxav1Vzja7A3O45AT4pbuc3hp qZAAgch7USwXlIOseMy7UCNFOk56XSPdDr0ClEMc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+37b56485bbbf90ad8489@syzkaller.appspotmail.com, Jiayuan Chen , Ihor Solodrai , Alexei Starovoitov Subject: [PATCH 6.18 395/395] bpf: Reject key-less BTF for hash maps Date: Wed, 30 Sep 2026 17:30:57 +0200 Message-ID: <20260930152349.270988946@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152340.591469096@linuxfoundation.org> References: <20260930152340.591469096@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiayuan Chen commit 0895a0c0734703be5532f3883c42db95615fd98b upstream. map_check_btf() allows a key-less BTF (btf_key_type_id == 0) only for maps that have a ->map_check_btf callback, and leaves the actual decision to that callback. Hash maps used to have no ->map_check_btf, so a key-less BTF was rejected outright. That changed when htab and rhtab gained a ->map_check_btf to register a dtor - htab in commit 1df97a7453ee ("bpf: Register dtor for freeing special fields") and rhtab in commit 6905f8601298 ("bpf: Allow special fields in resizable hashtab"). Neither looks at the key, so a key-less hash map now passes map_check_btf() and gets created. Reading it back through bpffs feeds the key type_id 0 into btf_type_seq_show(); btf_type_by_id() returns the void type, kind_ops[BTF_KIND_UNKN] is NULL, and btf_type_show() dereferences it: RIP: 0010:btf_type_show+0x223/0x2e0 kernel/bpf/btf.c:8232 RSP: 0018:ffffc9000399f868 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000028 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: ffffc9000399f970 R11: 0000000000000001 R12: ffffffff9b96b140 R13: ffffc9000399f8e0 R14: ffff88803d393c00 R15: 0000000000000003 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000000 CR3: 000000003d213000 CR4: 0000000000352ef0 DR0: 0000000039ae8f55 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Call Trace: btf_type_seq_show_flags+0xca/0x120 kernel/bpf/btf.c:8250 htab_map_seq_show_elem+0x12e/0x350 kernel/bpf/hashtab.c:1669 map_seq_show+0x13d/0x1e0 kernel/bpf/inode.c:293 traverse.part.0.constprop.0+0x107/0x650 fs/seq_file.c:112 traverse fs/seq_file.c:99 [inline] seq_read_iter+0x93f/0x1270 fs/seq_file.c:196 seq_read+0x344/0x4d0 fs/seq_file.c:163 vfs_read+0x1e4/0xb40 fs/read_write.c:572 ksys_pread64 fs/read_write.c:764 [inline] __do_sys_pread64 fs/read_write.c:772 [inline] __se_sys_pread64 fs/read_write.c:769 [inline] __x64_sys_pread64+0x1eb/0x250 fs/read_write.c:769 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f Reject a key-less BTF in htab_map_check_btf() and rhtab_map_check_btf(), restoring the previous behavior. Fixes: 1df97a7453ee ("bpf: Register dtor for freeing special fields") Fixes: 6905f8601298 ("bpf: Allow special fields in resizable hashtab") Reported-by: syzbot+37b56485bbbf90ad8489@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/6a8f4e88.27659fcc.2ceef7.0008.GAE@google.com/T/ Signed-off-by: Jiayuan Chen Acked-by: Ihor Solodrai Link: https://lore.kernel.org/r/20260901104924.346187-2-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/hashtab.c | 3 +++ 1 file changed, 3 insertions(+) --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -543,6 +543,9 @@ static int htab_map_check_btf(const stru { struct bpf_htab *htab = container_of(map, struct bpf_htab, map); + if (btf_type_is_void(key_type)) + return -EINVAL; + if (htab_is_prealloc(htab)) return 0; /*