From nobody Wed Jun 10 12:16:15 2026 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.5]) (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 41943399351; Tue, 9 Jun 2026 12:53:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.5 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781009619; cv=none; b=ATOnOBnYGqY1vL5haWCgC1zQpordHfKkXa/Dc8z8mYNMXi13IJpJpOYqebYgjLmSZ8mbYmf9BfMDQDL5Ve8lKsfWAOLncv+dIznilRUG+Y1VV9u52tdrMSczk4q8JEiJz+FHs6TvcoxasOeJd43cjPvCwr6sDfza1eYTA0wRHCQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781009619; c=relaxed/simple; bh=YNxZ/YO140sFwyflBdzBe4JKsnOsi20InoK8tYuRJr0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BQe0EOLQx7wilynufjHrQOW8O2wpKF8ZziSQ+WYxn2Aw2yTVe0Wqj5TYzT8eS60Yp5Ayha1knwlZFfG1Ts1jSe1npZlumsl/tIZ0jrXEeTX9FIRKbk1U/9W0NV9eje+cnK9fzw5sQBqBb+BGrp2gYdeW6wZsSqi9ilssqhJEFOc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=UZ49X4zr; arc=none smtp.client-ip=220.197.31.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="UZ49X4zr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=X4 VJPfnT108rWbi8XePHBDXGaFZvJKhHWyZuhhK5KuA=; b=UZ49X4zrd0pbMsynCi FK1huilolJXnIBgGveUscdM5l+XEwWlP2r0HuHcEZqrcGwwlP6VTB1ph8lal85tW 6QL7CNYVDzPfkLsJHNusg+rxEQ/yaKw1rhlQzhm1C0iXMhZi6OmESazDeBfSu457 sDmp+dE0XSjCTom9vGnz8bJ3M= Received: from nec8-i7 (unknown []) by gzga-smtp-mtada-g1-4 (Coremail) with SMTP id _____wBXfwCHDChqml32CQ--.44113S3; Tue, 09 Jun 2026 20:52:30 +0800 (CST) From: chenyuan_fl@163.com To: chenyuan_fl@163.com Cc: andrii@kernel.org, ast@kernel.org, bot+bpf-ci@kernel.org, bpf@vger.kernel.org, chenyuan@kylinos.cn, clm@meta.com, daniel@iogearbox.net, eddyz87@gmail.com, ihor.solodrai@linux.dev, jolsa@kernel.org, linux-kernel@vger.kernel.org, martin.lau@kernel.org, martin.lau@linux.dev, memxor@gmail.com, song@kernel.org, yonghong.song@linux.dev Subject: [PATCH bpf v6 1/2] bpf: Fix kfunc implicit arg inject type detection to prevent invalid pointer deref Date: Tue, 9 Jun 2026 20:52:13 +0800 Message-ID: <20260609125214.3096351-2-chenyuan_fl@163.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260609125214.3096351-1-chenyuan_fl@163.com> References: <20260608142618.3064380-1-chenyuan_fl@163.com> <20260609125214.3096351-1-chenyuan_fl@163.com> 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 X-CM-TRANSID: _____wBXfwCHDChqml32CQ--.44113S3 X-Coremail-Antispam: 1Uf129KBjvJXoWxWr1xAr4kAryDAr4xKryUZFb_yoW7JrW5pF WrXr1qkr4kGw4xKwn3Ar4fAry5uw4fZa13JF4kGFyFvan8Ww4SqrsYkry3uF90yr15JF42 qw1qqrWqgFyUAaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0zir-BtUUUUU= X-CM-SenderInfo: xfkh05pxdqswro6rljoofrz/xtbDAg-KiGooDI-jywAA3m Content-Type: text/plain; charset="utf-8" From: Yuan Chen When a module kfunc declares an implicit struct bpf_prog_aux * argument, the verifier must identify it so the kernel injects env->prog->aux into the correct register at runtime. The original check used is_kfunc_arg_prog_aux() which calls btf_types_are_same() to compare the module BTF type against vmlinux. Root Cause This issue was triggered by pahole 1.30 generating module BTF with incorrect type information, which caused the kernel's distilled base BTF deduplication for modules to fail. As a result, the module retained its own copy of struct bpf_prog_aux with a different BTF ID than vmlinux's definition. While pahole 1.31 fixed the BTF generation issue, the kernel must be robust against such inconsistencies: a BTF mismatch should result in a clean rejection, not a kernel crash or information disclosure. When the distilled base dedup fails and btf_types_are_same() cannot match the module's bpf_prog_aux type against vmlinux's, is_kfunc_arg_prog_aux() returned false and the code fell through silently without setting arg_prog. The kfunc then received whatever value was in the argument register and dereferenced it as a bpf_prog_aux pointer, leading to: BUG: kernel invalid pointer dereference, address: 00000000000009e2 RIP: bpf_prog_get_assoc_struct_ops+0xa/0xc0 RDI: 0x000000000000046d (stale register value) In the observed crash the stale value was the process PID, causing a dereference within the unmapped NULL page. However, an attacker able to control the register value -- for example by writing a BPF program that explicitly sets R2 before calling a KF_IMPLICIT_ARGS kfunc -- could redirect the dereference to arbitrary kernel memory, turning this into an information disclosure. The fix ensures the verifier either validates and injects the correct bpf_prog_aux pointer, or rejects the program outright -- no silent fallthrough that could be exploited. Crash Stack Trace PID: 1133 TASK: ffff8881057d3900 CPU: 3 COMMAND: "test_progs" #0 machine_kexec at ffffffff812f6e26 #1 __crash_kexec at ffffffff8145a788 #2 crash_kexec at ffffffff8145ac24 #3 oops_end at ffffffff812bb67c #4 page_fault_oops at ffffffff813053a1 #5 exc_page_fault at ffffffff828e60a1 #6 asm_exc_page_fault at ffffffff810012a6 [exception RIP: bpf_prog_get_assoc_struct_ops+10] RIP: ffffffff815c024a RSP: ffffc90001b57e48 RFLAGS: 00010283 RAX: ffff8881057d3900 RBX: ffffc90001b57e68 RCX: ffff8881057d3900 RDX: 0000607d4d1768b8 RSI: 000000000000046d RDI: 000000000000046d #7 bpf_kfunc_multi_st_ops_test_1_assoc at ffffffffc0013a85 [bpf_testmod] #8 bpf_trace_run2 at ffffffff814f8332 #9 __traceiter_sys_enter at ffffffff81415f45 #10 trace_syscall_enter at ffffffff81416735 #11 do_syscall_64 at ffffffff828e06a1 Fix Split the combined is_kfunc_arg_ignore() || is_kfunc_arg_implicit() check in check_kfunc_args() so that an implicit argument reaching is_kfunc_arg_implicit() without being handled by a prior handler is rejected with -EFAULT, instead of silently skipped. Existing implicit args in bpf_fixup_kfunc_call() (obj_new, percpu_obj_new, obj_drop, percpu_obj_drop, refcount_acquire, list_push, rbtree_add) are explicitly allowed. Suggested-by: Eduard Zingerman Fixes: 64e1360524b9 ("bpf: Verifier support for KF_IMPLICIT_ARGS") Signed-off-by: Yuan Chen --- kernel/bpf/verifier.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8ed484cb1a8a..0d598a419008 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11885,9 +11885,28 @@ static int check_kfunc_args(struct bpf_verifier_en= v *env, struct bpf_kfunc_call_ continue; } =20 - if (is_kfunc_arg_ignore(btf, &args[i]) || is_kfunc_arg_implicit(meta, i)) + if (is_kfunc_arg_ignore(btf, &args[i])) continue; =20 + if (is_kfunc_arg_implicit(meta, i)) { + /* + * This is an exhaustive list of the non-bpf_prog_aux + * implicit args kfuncs, which are handled + * post-verification by bpf_fixup_kfunc_call(). + */ + if (is_bpf_obj_new_kfunc(meta->func_id) || + is_bpf_percpu_obj_new_kfunc(meta->func_id) || + is_bpf_obj_drop_kfunc(meta->func_id) || + is_bpf_percpu_obj_drop_kfunc(meta->func_id) || + is_bpf_refcount_acquire_kfunc(meta->func_id) || + is_bpf_list_push_kfunc(meta->func_id) || + is_bpf_rbtree_add_kfunc(meta->func_id)) + continue; + verbose(env, "%s unrecognized implicit argument, possible BTF mismatch\= n", + reg_arg_name(env, argno)); + return -EFAULT; + } + t =3D btf_type_skip_modifiers(btf, args[i].type, NULL); =20 if (btf_type_is_scalar(t)) { --=20 2.54.0 From nobody Wed Jun 10 12:16:15 2026 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.4]) (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 0367441930D; Tue, 9 Jun 2026 12:53:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.4 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781009624; cv=none; b=A7oWCXKyDWJcgWrSoNknjN1F71u6oNLwuzHNFtq4GjQrSjM6vOKdUE9x0g9A/IU9jjFG9ObdEfNW1An06P0y+b6+5+bNYEAr9Bn1AhjL1etHjrd3VblC8bsOwUvGFounA70YJrCXJcBjcpCtpMbTp3xTEzX+qRk3SVzzMElSqNQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781009624; c=relaxed/simple; bh=hKq87oloK4wQOobWABNNaOIg2C7pwg1eUmkYrjTqUaw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cqmy5UtisjC5C9FxfkDqDv8dCpUWij3jz4L5feSJKN95jqtGm0KPfFim9U5aEvbqVcT7/fr9N6J6jooMq4zs6Ndj1zW65hLUd+KeRQRRSmxwTUzBXyMr44peuw1XtOmyOfIpzp2IHRwaF8iHUtYYagaR2ibZW2VrnxnXcf1Gh9s= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=ZkKwzQVb; arc=none smtp.client-ip=220.197.31.4 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="ZkKwzQVb" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=Lk u9J1QQClxXUHMC+AqzpMiIb0/zD0xqOOn1lD3TYNc=; b=ZkKwzQVbBrmWQSyeXw UIiQIcAPBLyihU8wDAuVFq7Q9HqpWhh+Xrs1bVrI3AmBCA++VYgzpDKuOw5ARnYN F2bpJy/bwfoiZtgeDdGf0wWaEnJ//+AxwLMe0ZL6cesTlPKFdEL+E53ysVU+j1x6 0fG4alVjvxShCmm9SQaq2NRIQ= Received: from nec8-i7 (unknown []) by gzga-smtp-mtada-g1-4 (Coremail) with SMTP id _____wBXfwCHDChqml32CQ--.44113S4; Tue, 09 Jun 2026 20:52:33 +0800 (CST) From: chenyuan_fl@163.com To: chenyuan_fl@163.com Cc: andrii@kernel.org, ast@kernel.org, bot+bpf-ci@kernel.org, bpf@vger.kernel.org, chenyuan@kylinos.cn, clm@meta.com, daniel@iogearbox.net, eddyz87@gmail.com, ihor.solodrai@linux.dev, jolsa@kernel.org, linux-kernel@vger.kernel.org, martin.lau@kernel.org, martin.lau@linux.dev, memxor@gmail.com, song@kernel.org, yonghong.song@linux.dev Subject: [PATCH bpf v6 2/2] selftests/bpf: strengthen bpf_kfunc_implicit_arg to verify aux injection Date: Tue, 9 Jun 2026 20:52:14 +0800 Message-ID: <20260609125214.3096351-3-chenyuan_fl@163.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260609125214.3096351-1-chenyuan_fl@163.com> References: <20260608142618.3064380-1-chenyuan_fl@163.com> <20260609125214.3096351-1-chenyuan_fl@163.com> 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 X-CM-TRANSID: _____wBXfwCHDChqml32CQ--.44113S4 X-Coremail-Antispam: 1Uf129KBjvJXoW7WFW8WF1ftry5ury5Gw48WFg_yoW8XFy3pa 97Jr10kr97Xa17XFn7GF48XFWrKFs3XrW8AF1DGr95Zr4kX340qF18tFyFvFnI9r4Fq3Wf AayxKFW5uw48ZaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0zR1rWrUUUUU= X-CM-SenderInfo: xfkh05pxdqswro6rljoofrz/xtbC5hLLiWooDJK5bAAA3- Content-Type: text/plain; charset="utf-8" From: Yuan Chen Verify that the KF_IMPLICIT_ARGS injection path correctly passes the bpf_prog_aux pointer by checking aux->name in bpf_kfunc_implicit_arg() for the expected program name prefix. If the verifier incorrectly skipped injection (as could happen with pahole 1.30's BTF mismatch), the stale register would not contain a valid aux pointer and the name check would fail. This is a positive test exercised by the existing kfunc_implicit_args selftest, which calls bpf_kfunc_implicit_arg(5) and expects a return value of 5. Signed-off-by: Yuan Chen --- tools/testing/selftests/bpf/test_kmods/bpf_testmod.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/t= esting/selftests/bpf/test_kmods/bpf_testmod.c index 30f1cd23093c..624d57a5c79a 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c @@ -1906,7 +1906,11 @@ int bpf_kfunc_multi_st_ops_test_1_assoc(struct st_op= s_args *args, struct bpf_pro =20 int bpf_kfunc_implicit_arg(int a, struct bpf_prog_aux *aux) { - if (aux && a > 0) + /* Verify the kernel injected the correct bpf_prog_aux pointer + * rather than leaving a stale register value. */ + if (!aux || strncmp(aux->name, "test_kfunc", sizeof("test_kfunc") - 1)) + return -EINVAL; + if (a > 0) return a; return -EINVAL; } --=20 2.54.0