From nobody Sat Sep 26 13:08:13 2026 Received: from mta0.migadu.com (out-214.mta0.migadu.com [91.218.175.214]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F2A3847DD74 for ; Tue, 1 Sep 2026 10:50:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.214 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788259828; cv=none; b=hW4EWeGhyl4GkfcUI3FpoFn6NGYMv0rdb8hmEhx9Uy6V625STG6wekM2RO+dNlf9jLQDgjscBKX/392r7VL68W40mkLlwjNWcsmKPN7IzDfkniKnn+oME/27T6Yjn16eFst+8iVsF7DBExIAiuRLeBtbnQEFguh8z4mAh0Kt/jU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788259828; c=relaxed/simple; bh=C1F/at+ZpcyorQfJWG9U8cQlYWLtImAZlUOYJDjZBzI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Iti0nIfn9VFCRwtp9rrHKwEhYo1jCR2ialOjNSCdN7OrRA0TOBBjU8oixMmfIpEUmKrM8rrdwbbjWhNOuCSl8M3vl5wLdItx1SoMzPXGAZ/4I1zEL9DegR5cGZ0zBvBHw32bF+2rzIpucYYX1QBxdixU4MfpY0pMG6JcNwDe6Jc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=HHuF9GYy; arc=none smtp.client-ip=91.218.175.214 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="HHuF9GYy" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=C1F/at+ZpcyorQfJWG9U8cQlYWLtImAZlUOYJDjZBzI=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788259825; v=1; x=1788864625; b=HHuF9GYyS4WSoVgIehCZYROVFwhQ0t5ZviCBNC6SjLVpoJfKPwlmsoa3eY+ivE//k8ZwUkXR t5/n6LO92oK1/zR1h9BuNCGJnXpbcnrtbx3cR+BBWRXaKrVh/8s09EUFHrBQQIOjmDkDqlux7pX GEHDKn61y1HH6QfnrbLWIHRc= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id d642d75bbf501021; Tue, 01 Sep 2026 10:50:24 +0000 X-Mizu-Trace-ID: d642d75bbf501021 X-Migadu-Flow: FLOW_OUT From: Jiayuan Chen To: bpf@vger.kernel.org Cc: Jiayuan Chen , syzbot+37b56485bbbf90ad8489@syzkaller.appspotmail.com, Ihor Solodrai , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Shuah Khan , Mykyta Yatsenko , Alan Maguire , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf v4 1/5] bpf: Reject key-less BTF for hash maps Date: Tue, 1 Sep 2026 18:47:35 +0800 Message-ID: <20260901104924.346187-2-jiayuan.chen@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260901104924.346187-1-jiayuan.chen@linux.dev> References: <20260901104924.346187-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" map_check_btf() allows a key-less BTF (btf_key_type_id =3D=3D 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@googl= e.com/T/ Signed-off-by: Jiayuan Chen Acked-by: Ihor Solodrai --- kernel/bpf/hashtab.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index d40cb5dd446c..7f55d6421e72 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -530,6 +530,9 @@ static int htab_map_check_btf(struct bpf_map *map, cons= t struct btf *btf, { struct bpf_htab *htab =3D container_of(map, struct bpf_htab, map); =20 + if (btf_type_is_void(key_type)) + return -EINVAL; + if (htab_is_prealloc(htab)) return 0; /* @@ -3110,6 +3113,9 @@ static int rhtab_map_check_btf(struct bpf_map *map, c= onst struct btf *btf, { struct bpf_rhtab *rhtab =3D container_of(map, struct bpf_rhtab, map); =20 + if (btf_type_is_void(key_type)) + return -EINVAL; + return bpf_ma_set_dtor(map, &rhtab->ma, rhtab_mem_dtor); } =20 --=20 2.43.0 From nobody Sat Sep 26 13:08:13 2026 Received: from mta1.migadu.com (out-2.mta1.migadu.com [95.215.58.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0393A472089 for ; Tue, 1 Sep 2026 10:50:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.2 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788259853; cv=none; b=IfqzrDfMgDLO+xJJj3mrjUzQleZWjsPxdh0SkD7t68kzkYFNMmh16MSdi0tUHWa4hjuSYSeOtg9xu9s2e90kYUrftX7Z1ZcPAegHwYFL+C1M6JGTdxuar19E5iAkiPQjM1CXn+uCG134CVtU088NsjVjhZQx1mbov+sdvqP4I/U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788259853; c=relaxed/simple; bh=gPKpCL1/0/HGOmJCv2o0g9Ep/ccfdyIwBD6hFRIQHy4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=naXaNlZsUMsCiVM+XDbLO9M2jOSoUcL3D/JwDP0+pRWZexBVe4FJsSq2mPSOnc3RK69L9tlb+NE5WmohBPUht2a8e0A3WUW9Ovu1HL+mCMmJl09jdQH9u78HopJqDwuCdYvevBpQWas5S7MiRdVf/T4vBmNZeu9SFtwITIOFJ7M= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=uEJYFSbr; arc=none smtp.client-ip=95.215.58.2 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="uEJYFSbr" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=gPKpCL1/0/HGOmJCv2o0g9Ep/ccfdyIwBD6hFRIQHy4=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788259849; v=1; x=1788864649; b=uEJYFSbro7W7xdPBNUVefEqxyrraOEozoGq7QcvFvtumYFUE7sBxrCKk9eRIxIgGlRho0lWS et8UuFbh0N+9DzU3fdq9lAV8EJf0LNlwf0lzMbkkQ96qVdPEq2ZpFceZT2bbETHxxCvWyDeBOr9 KIpx3HIz3GDm6AAUdXBFKa68= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 41aadf1de9cb078d; Tue, 01 Sep 2026 10:50:49 +0000 X-Mizu-Trace-ID: 41aadf1de9cb078d X-Migadu-Flow: FLOW_OUT From: Jiayuan Chen To: bpf@vger.kernel.org Cc: Jiayuan Chen , Ihor Solodrai , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Shuah Khan , Mykyta Yatsenko , Alan Maguire , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf v4 2/5] bpf: Fix NULL-ptr-deref when showing a void BTF type Date: Tue, 1 Sep 2026 18:47:36 +0800 Message-ID: <20260901104924.346187-3-jiayuan.chen@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260901104924.346187-1-jiayuan.chen@linux.dev> References: <20260901104924.346187-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" btf_modifier_show() resolves the modifier and then calls btf_type_ops(t)->show() unconditionally. For the void type (type_id 0, BTF_KIND_UNKN) kind_ops[] has no entry, so ->show is NULL. A "const void" (a modifier resolving to void) cannot be a map key or value - map_check_btf() rejects it because void has no size - so the map dump path does not reach it. But bpf_snprintf_btf() takes a type_id straight from the BPF program, and passing such a "const void" from the vmlinux BTF NULL-derefs: KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] RIP: 0010:btf_modifier_show (kernel/bpf/btf.c:2914) Call Trace: btf_type_show (kernel/bpf/btf.c:8251) btf_type_snprintf_show (kernel/bpf/btf.c:8321) bpf_snprintf_btf (kernel/trace/bpf_trace.c:1047) bpf_prog_test_run_raw_tp (net/bpf/test_run.c:829) __sys_bpf (kernel/bpf/syscall.c:4804) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Fall back to btf_df_show() when the resolved type has no show op; it emits the "" placeholder already used for kinds like FWD and FUNC. bpf_snprintf_btf() then returns the length as usual. Fixes: c4d0bfb45068 ("bpf: Add bpf_snprintf_btf helper") Signed-off-by: Jiayuan Chen Acked-by: Ihor Solodrai --- re bot+bpf-ci: a "const void" is a modifier with a nonzero type_id, so map_check_btf() rejects it as key or value on the size check. The bare void key (id 0) is a different path, handled by patch 1. re sashiko-bot: btf_var_show() has the same bug, fixed in patch 3. --- kernel/bpf/btf.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 91b8ce77f699..7835fe201384 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -2911,7 +2911,14 @@ static void btf_modifier_show(const struct btf *btf, else t =3D btf_type_skip_modifiers(btf, type_id, NULL); =20 - btf_type_ops(t)->show(btf, t, type_id, data, bits_offset, show); + /* + * A modifier can resolve to void, which has no show op; print a + * placeholder rather than dereferencing NULL. + */ + if (!btf_type_ops(t)) + btf_df_show(btf, t, type_id, data, bits_offset, show); + else + btf_type_ops(t)->show(btf, t, type_id, data, bits_offset, show); } =20 static void btf_var_show(const struct btf *btf, const struct btf_type *t, --=20 2.43.0 From nobody Sat Sep 26 13:08:13 2026 Received: from mta0.migadu.com (out-233.mta0.migadu.com [91.218.175.233]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E97263AAF54 for ; Tue, 1 Sep 2026 10:51:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.233 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788259879; cv=none; b=Njoa6SfBA9Ip2f/qnTBEBSNurRS67lZikri/KB9Egie2ScB0HOkdmskZ88KJqw9sRwjDZ0aAFWBjn7VyxrJnH2WAqgaJw7T2I1quOLBXXJbcgT8OpyNjoC5hfaMdIgwUh3APZULMtJHUaCW6Vow7RQYwu2wW/exVNY4e+uEejCI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788259879; c=relaxed/simple; bh=edHUuQXAD8zD3HIZyMJ5TXVcUbJG2wFP7sF8oZ3FG3k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nRwfh3BWB8tm5LrnYLYG+DmquqoEk746CjRNNZgis/ITQr9dEgWBlYSUi4TcozJZ2eTU8otNPqu7onkZZtxQET6lXCyS1CLfZ8on5xM3tiRxcMtaW/HoW+QA9pB53JD1G04SEWIy7bw0rtXilQQKlb+hSRf1mvCrljDBSt0jNbw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=WLgHcUdn; arc=none smtp.client-ip=91.218.175.233 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="WLgHcUdn" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=edHUuQXAD8zD3HIZyMJ5TXVcUbJG2wFP7sF8oZ3FG3k=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788259874; v=1; x=1788864674; b=WLgHcUdn64zDH6jeEEcgMteCSzphLgYQeZ3fnW7bYSiYRAn6xg4DkwbdukdlpAqrL8MX/Gpx I1WPML+a5lPoBv+lEBtSh5nMT52DomBDYGwHsL522TbncaSkNkVbCYY23jLvLKIloGYyN4HeZtd +uDMue9J78/yJh6/CNyOmBBw= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 59ba207f978f01a8; Tue, 01 Sep 2026 10:51:14 +0000 X-Mizu-Trace-ID: 59ba207f978f01a8 X-Migadu-Flow: FLOW_OUT From: Jiayuan Chen To: bpf@vger.kernel.org Cc: Jiayuan Chen , Ihor Solodrai , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Shuah Khan , Mykyta Yatsenko , Alan Maguire , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf v4 3/5] bpf: Fix NULL-ptr-deref in btf_var_show() Date: Tue, 1 Sep 2026 18:47:37 +0800 Message-ID: <20260901104924.346187-4-jiayuan.chen@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260901104924.346187-1-jiayuan.chen@linux.dev> References: <20260901104924.346187-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" btf_var_show() calls btf_type_id_resolve() unconditionally, which dereferences btf->resolved_ids. That is NULL for a base BTF - e.g. the vmlinux BTF that bpf_snprintf_btf() renders against - since base BTF is not resolved during parsing. btf_modifier_show() guards this with 'if (btf->resolved_ids)', but btf_var_show() does not. A BPF program that passes the type_id of a BTF_KIND_VAR from the vmlinux BTF to bpf_snprintf_btf() thus NULL-derefs: KASAN: probably user-memory-access in range [0x46638-0x4663f] RIP: 0010:btf_var_show (kernel/bpf/btf.c:2929) Call Trace: btf_type_show (kernel/bpf/btf.c:8259) btf_type_snprintf_show (kernel/bpf/btf.c:8329) bpf_snprintf_btf (kernel/trace/bpf_trace.c:1047) bpf_prog_test_run_raw_tp (net/bpf/test_run.c:829) __sys_bpf (kernel/bpf/syscall.c:4804) do_syscall_64 (arch/x86/entry/syscall_64.c:84) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Resolve the var's type directly with btf_type_skip_modifiers() when resolved_ids is NULL, mirroring btf_modifier_show(). Fixes: c4d0bfb45068 ("bpf: Add bpf_snprintf_btf helper") Signed-off-by: Jiayuan Chen Acked-by: Ihor Solodrai --- kernel/bpf/btf.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 7835fe201384..7c634d639b7f 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -2925,7 +2925,15 @@ static void btf_var_show(const struct btf *btf, cons= t struct btf_type *t, u32 type_id, void *data, u8 bits_offset, struct btf_show *show) { - t =3D btf_type_id_resolve(btf, &type_id); + /* + * btf_type_id_resolve() dereferences btf->resolved_ids, which is NULL + * for a base BTF (e.g. the vmlinux BTF that bpf_snprintf_btf() uses). + * Resolve the var's type directly in that case. + */ + if (btf->resolved_ids) + t =3D btf_type_id_resolve(btf, &type_id); + else + t =3D btf_type_skip_modifiers(btf, t->type, &type_id); =20 btf_type_ops(t)->show(btf, t, type_id, data, bits_offset, show); } --=20 2.43.0 From nobody Sat Sep 26 13:08:13 2026 Received: from mta0.migadu.com (out-246.mta0.migadu.com [91.218.175.246]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE817396B96 for ; Tue, 1 Sep 2026 10:51:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.246 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788259905; cv=none; b=WmPXaV8TQemPQiYeJgo4jR19Z9wnDOj6+uRGwcc+HXO1+ELvdzUjHMBkTbJD6ZfdkuPCSAcrPvT/cCfasB2lwT7dlpaDKAXBJX5WWAV/Tyi0KOc8NYngonVAyR03e2xegyR3bK6US3JNSpUXS1PwLIQRvK5M/Q8Gxm496FHuU/0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788259905; c=relaxed/simple; bh=mxQjvG+VqIP1YaBTpqWzujFAX1hh8VeTZFGeGZcTtBk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Jf0M/4Gg/xL7Syq2vpxWsjikldAApl4r6nRIEWke+gDHVllMXz/0u3Y6aQ/BhRpKujsy02qx3teqjUKNHsE7nL7MWUDY7gs+qZo6GT0zTIbmbLTGiH9V5sE8Fna+Ud7rDaa83GS5NODebyQI5ih0kCmg7XK3XmbEgbM42yOJjeo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=xrYzOQ0W; arc=none smtp.client-ip=91.218.175.246 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="xrYzOQ0W" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=mxQjvG+VqIP1YaBTpqWzujFAX1hh8VeTZFGeGZcTtBk=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788259899; v=1; x=1788864699; b=xrYzOQ0WTc+1CmkxFa7e7NFWzqjrumzovvNob7xY4gUWFUOU73MePOkMzbq5v++VF8E5JKN+ cZ5sWO5cP/HuKOOCbLCK8pNmccq1bRKgegFJo2aqfWplFDOifs3+KPVu2ZC2XqogPKyH8qWzyKa StipbekJDXzG8HStm1l3sIu0= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 91a937191a82c02f; Tue, 01 Sep 2026 10:51:39 +0000 X-Mizu-Trace-ID: 91a937191a82c02f X-Migadu-Flow: FLOW_OUT From: Jiayuan Chen To: bpf@vger.kernel.org Cc: Jiayuan Chen , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Shuah Khan , Mykyta Yatsenko , Alan Maguire , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf v4 4/5] selftests/bpf: Add test for key-less BTF hash map Date: Tue, 1 Sep 2026 18:47:38 +0800 Message-ID: <20260901104924.346187-5-jiayuan.chen@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260901104924.346187-1-jiayuan.chen@linux.dev> References: <20260901104924.346187-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Create a hash and an rhash map with btf_key_type_id =3D=3D 0 and expect bpf_map_create() to fail with -EINVAL; a positive control with a real key type confirms the rejection is about the key-less BTF and not some unrelated failure. Such a map used to be accepted and then NULL-deref in btf_type_show() when dumped through bpffs. Signed-off-by: Jiayuan Chen --- re bot+bpf-ci: the positive control is on purpose. Without it, if the map type is missing both creates return -EINVAL and the key-less check would pass for the wrong reason. --- .../bpf/prog_tests/btf_map_keyless.c | 59 +++++++++++++++++++ 1 file changed, 59 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/btf_map_keyless.c diff --git a/tools/testing/selftests/bpf/prog_tests/btf_map_keyless.c b/too= ls/testing/selftests/bpf/prog_tests/btf_map_keyless.c new file mode 100644 index 000000000000..3248bccc3557 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/btf_map_keyless.c @@ -0,0 +1,59 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include + +/* + * A hash map with a key-less BTF (btf_key_type_id =3D=3D 0) used to be ac= cepted + * and then NULL-deref in btf_type_show() when dumped through bpffs. A fix= ed + * kernel rejects it at creation; verify that rejection, with a keyed posi= tive + * control so the -EINVAL is about the missing key type and not some unrel= ated + * failure. + */ +static void check_keyless(int map_type, __u32 map_flags, int btf_fd, int v= al_id) +{ + LIBBPF_OPTS(bpf_map_create_opts, opts); + int map_fd; + + opts.map_flags =3D map_flags; + opts.btf_fd =3D btf_fd; + opts.btf_value_type_id =3D val_id; + + /* Positive control: the same map with a real key type is accepted. */ + opts.btf_key_type_id =3D val_id; + map_fd =3D bpf_map_create(map_type, "keyed_map", 4, 4, 8, &opts); + if (!ASSERT_GE(map_fd, 0, "keyed create is accepted")) + return; + close(map_fd); + + /* A key-less BTF must be rejected. */ + opts.btf_key_type_id =3D 0; + map_fd =3D bpf_map_create(map_type, "keyless_map", 4, 4, 8, &opts); + ASSERT_EQ(map_fd, -EINVAL, "key-less create is rejected"); + if (map_fd >=3D 0) + close(map_fd); +} + +void test_btf_map_keyless(void) +{ + int btf_fd, val_id; + struct btf *btf; + + btf =3D btf__new_empty(); + if (!ASSERT_OK_PTR(btf, "btf__new_empty")) + return; + + val_id =3D btf__add_int(btf, "int", 4, BTF_INT_SIGNED); + if (!ASSERT_GT(val_id, 0, "btf__add_int")) + goto out; + + if (!ASSERT_OK(btf__load_into_kernel(btf), "btf__load_into_kernel")) + goto out; + btf_fd =3D btf__fd(btf); + + if (test__start_subtest("hash")) + check_keyless(BPF_MAP_TYPE_HASH, 0, btf_fd, val_id); + if (test__start_subtest("rhash")) + check_keyless(BPF_MAP_TYPE_RHASH, BPF_F_NO_PREALLOC, btf_fd, val_id); +out: + btf__free(btf); +} --=20 2.43.0 From nobody Sat Sep 26 13:08:13 2026 Received: from mta1.migadu.com (out-38.mta1.migadu.com [95.215.58.38]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D968D47A873 for ; Tue, 1 Sep 2026 10:52:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.38 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; 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spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="YxhoECTe" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=Lw7FlsSYwx9NIxyyRCjoPzXtc3uYAtj1sWqV4v49tus=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788259924; v=1; x=1788864724; b=YxhoECTepcZG0pY/Ya36r7O1nffsLoGLNOqJjE+iK6sOKVplMhnweao/xHO/A6Oa+psAR1d3 IN8CnTkC4HFgl1h9kvyq7jMHMvRD4WWw94sNgk/BpVfzUDLbT9gkddkpXNUdfYGFUhgEV/BCiRQ oLwQJDfhvUcyz086Tsiwj+pw= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 66d397e71cc3a3e9; Tue, 01 Sep 2026 10:52:04 +0000 X-Mizu-Trace-ID: 66d397e71cc3a3e9 X-Migadu-Flow: FLOW_OUT From: Jiayuan Chen To: bpf@vger.kernel.org Cc: Jiayuan Chen , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Shuah Khan , Mykyta Yatsenko , Alan Maguire , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf v4 5/5] selftests/bpf: Add test for showing a void BTF type Date: Tue, 1 Sep 2026 18:47:39 +0800 Message-ID: <20260901104924.346187-6-jiayuan.chen@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260901104924.346187-1-jiayuan.chen@linux.dev> References: <20260901104924.346187-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Extend the snprintf_btf test with type_ids from the vmlinux BTF that used to NULL-deref in the BTF show path: a "const void", checked to render the "" placeholder, and a BTF_KIND_VAR, checked to resolve and render without error. The program renders from its own buffer and the test picks a VAR whose resolved type fits it, so the render stays in bounds. Signed-off-by: Jiayuan Chen --- .../selftests/bpf/prog_tests/snprintf_btf.c | 79 +++++++++++++++++++ .../selftests/bpf/progs/snprintf_btf_void.c | 24 ++++++ 2 files changed, 103 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/snprintf_btf_void.c diff --git a/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c b/tools/= testing/selftests/bpf/prog_tests/snprintf_btf.c index dd41b826be30..edce9c1b54fb 100644 --- a/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c +++ b/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c @@ -1,7 +1,9 @@ // SPDX-License-Identifier: GPL-2.0 #include #include +#include #include "netif_receive_skb.skel.h" +#include "snprintf_btf_void.skel.h" =20 /* Demonstrate that bpf_snprintf_btf succeeds and that various data types * are formatted correctly. @@ -58,3 +60,80 @@ void serial_test_snprintf_btf(void) cleanup: netif_receive_skb__destroy(skel); } + +/* + * bpf_snprintf_btf() renders a type_id taken straight from the vmlinux BT= F. + * Two such type_ids used to NULL-deref in the BTF show path: + * - a "const void" (a modifier resolving to void) in btf_modifier_show() + * - a BTF_KIND_VAR in btf_var_show() (base BTF has no resolved_ids) + * A fixed kernel renders both without crashing. + */ +static long run(struct snprintf_btf_void *skel, __u32 type_id) +{ + LIBBPF_OPTS(bpf_test_run_opts, topts); + char ctx[8] =3D {}; + + skel->bss->type_id =3D type_id; + topts.ctx_in =3D ctx; + topts.ctx_size_in =3D sizeof(ctx); + if (!ASSERT_OK(bpf_prog_test_run_opts(bpf_program__fd(skel->progs.dump_ty= pe), + &topts), "test_run")) + return -1; + return skel->bss->ret; +} + +void test_snprintf_btf_void(void) +{ + const struct btf_type *t; + struct snprintf_btf_void *skel; + int i, n, cv =3D 0, var =3D 0; + struct btf *btf; + + btf =3D btf__parse("/sys/kernel/btf/vmlinux", NULL); + if (!btf) { + test__skip(); + return; + } + + skel =3D snprintf_btf_void__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_open_and_load")) + goto out_btf; + + n =3D btf__type_cnt(btf); + for (i =3D 1; i < n && !(cv && var); i++) { + t =3D btf__type_by_id(btf, i); + if (!cv && btf_kind(t) =3D=3D BTF_KIND_CONST && t->type =3D=3D 0) + cv =3D i; + /* Pick a VAR small enough to render from the program's buffer. */ + if (!var && btf_kind(t) =3D=3D BTF_KIND_VAR) { + long sz =3D btf__resolve_size(btf, t->type); + + if (sz > 0 && sz <=3D (long)sizeof(skel->bss->obj)) + var =3D i; + } + } + + /* "const void" renders the "" placeholder. */ + if (test__start_subtest("const_void")) { + if (cv) { + ASSERT_EQ(run(skel, cv), + sizeof("") - 1, "ret"); + ASSERT_STREQ(skel->bss->out, "", + "placeholder"); + } else { + test__skip(); + } + } + + /* A BTF_KIND_VAR must resolve and render without error. */ + if (test__start_subtest("var")) { + if (var) + ASSERT_GT(run(skel, var), 0, "ret"); + else + test__skip(); + } + + snprintf_btf_void__destroy(skel); +out_btf: + btf__free(btf); +} diff --git a/tools/testing/selftests/bpf/progs/snprintf_btf_void.c b/tools/= testing/selftests/bpf/progs/snprintf_btf_void.c new file mode 100644 index 000000000000..44af80fbbb80 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/snprintf_btf_void.c @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "btf_ptr.h" +#include + +__u32 type_id; +/* A buffer we own to render the selected type from, kept in bounds. */ +char obj[256]; +char out[64]; +long ret; + +SEC("raw_tp/sys_enter") +int dump_type(void *ctx) +{ + struct btf_ptr ptr =3D { + .ptr =3D obj, + .type_id =3D type_id, + .flags =3D 0, + }; + + ret =3D bpf_snprintf_btf(out, sizeof(out), &ptr, sizeof(ptr), 0); + return 0; +} + +char _license[] SEC("license") =3D "GPL"; --=20 2.43.0