From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from azure-sdnproxy.icoremail.net (azure-sdnproxy.icoremail.net [13.76.78.106]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 00B4B312803; Mon, 22 Jun 2026 02:26:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.76.78.106 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782095198; cv=none; b=a1D/CdbE2wKHN8xddzf7iOFjdvo4Km/D9wedNxZ4T6Ck3JtPmzX8kqjnvs5CVzyYfVQy64RX20zoBJ/b6cB1ZgESf1+DM98TtzRgaSFM8S2IAuTeGpE+G5Ms2VPYKD17vT2Z4Y70/FncZe2BumsFISBmKraI6cBAiXr19svbLt4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782095198; c=relaxed/simple; bh=jfX9bbXwEAn2RIE/tOqMtrsGH9uMCaFLjXlT9MmoLJg=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=mIXoxr+r9AnN3T6iDPxdxANLcytafNrYhFSTAtXxxGEj5O/JbP7j4RCoXmirtcSFO6JXMpuoa+eOJHYMX3bzbKjuK2YgR0sixTRyL0S27ckgSn0WP4J1ZUeyl4GdEE3SRDHw8PR+/LaCZEjZqfcF3oyJuMlzb7ebOi4FTLSLR0w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mails.tsinghua.edu.cn; spf=pass smtp.mailfrom=mails.tsinghua.edu.cn; dkim=pass (1024-bit key) header.d=mails.tsinghua.edu.cn header.i=@mails.tsinghua.edu.cn header.b=oWnBGItJ; arc=none smtp.client-ip=13.76.78.106 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mails.tsinghua.edu.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mails.tsinghua.edu.cn Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=mails.tsinghua.edu.cn header.i=@mails.tsinghua.edu.cn header.b="oWnBGItJ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mails.tsinghua.edu.cn; s=dkim; h=Received:From:To:Cc:Subject: Date:Message-Id:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=QhPbn/Ffv7vIq715w4RbiIsqdEaBuGnIsw sZGv4+yKs=; b=oWnBGItJpzggIxAD+n8Zw8oSWB1CnZ28np9cygjNyWAudBEVhr W7ycx+ncUZrw/ddXJgM+Ae2hmc3ZBaX3MpHKvWJ/gD6FO6mWXOB47jhV0zj/pphK 473Zaq9Vul/xmaNtuO/KbuH0vTjOeYCxttOP4RA1qc5tZoKJOj3ZZXfOY= Received: from c9a6c405b3f2.. (unknown [202.112.238.121]) by web5 (Coremail) with SMTP id zAQGZQCHQcEynThqj7qZAg--.19827S3; Mon, 22 Jun 2026 10:26:13 +0800 (CST) From: Yiyang Chen To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi Cc: Yiyang Chen , John Fastabend , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Shuah Khan , Viktor Malik , Leon Hwang , Dave Marchevsky , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next v3 1/2] bpf: Reject offset refcount acquire arguments Date: Mon, 22 Jun 2026 02:25:51 +0000 Message-Id: X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:zAQGZQCHQcEynThqj7qZAg--.19827S3 X-Coremail-Antispam: 1UD129KBjvJXoWxurW3uryfZF17Cr15ZF4DCFg_yoWrtrW7pa n5Kr92yr4ktayfuwsrtF4DAr95G34Fq3y3CFy8Aa4I9FyfWw1DJFZ09ryjq3WSk34kAwnr Ar1093sxZw15CF7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUd0b7Iv0xC_Cr1lb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I2 0VC2zVCF04k26cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI 8067AKxVWUGwA2048vs2IY020Ec7CjxVAFwI0_Gr0_Xr1l8cAvFVAK0II2c7xJM28CjxkF 64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcV CY1x0267AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv 6xkF7I0E14v26rxl6s0DM2vYz4IE04k24VAvwVAKI4IrM2AIxVAIcxkEcVAq07x20xvEnc xIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E 87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lF7I21c 0EjII2zVCS5cI20VAGYxC7M4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS14v26r4a 6rW5MxkIecxEwVAFwVW8JwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8Jw C20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAF wI0_GFv_WrylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjx v20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2 jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0x ZFpf9x0pEoGQxUUUUU= X-CM-SenderInfo: xfkh05r1stqzpdlo2hxwvl0wxkxdhvlgxou0/ bpf_refcount_acquire() increments the refcount at the caller-supplied pointer plus the refcount field offset, then returns the caller-supplied pointer unchanged. The verifier records the return value as a base pointer to the refcounted object. bpf_list_pop_front() and bpf_rbtree_remove() can return embedded graph-node pointers as PTR_TO_BTF_ID | MEM_ALLOC with a fixed offset equal to the node field offset. Passing such a pointer directly to bpf_refcount_acquire() currently passes the refcounted-kptr type check. That makes the runtime operation start from base + node_off while the verifier models the returned pointer as the object base. Require refcount-acquire arguments to have zero fixed offset by carrying the requirement through check_func_arg_reg_off() to __check_ptr_off_reg(). Programs can still acquire a refcount from a graph-node-derived pointer after normalizing it with container_of(). Fixes: 7c50b1cb76aca ("bpf: Add bpf_refcount_acquire kfunc") Signed-off-by: Yiyang Chen --- kernel/bpf/verifier.c | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2abc79dbf..f65eff28e 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7990,9 +7990,10 @@ reg_find_field_offset(const struct bpf_reg_state *reg, s32 off, u32 fields) return field; } -static int check_func_arg_reg_off(struct bpf_verifier_env *env, - const struct bpf_reg_state *reg, argno_t argno, - enum bpf_arg_type arg_type) +static int __check_func_arg_reg_off(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, argno_t argno, + enum bpf_arg_type arg_type, + bool btf_id_fixed_off_ok) { u32 type = reg->type; @@ -8049,12 +8050,11 @@ static int check_func_arg_reg_off(struct bpf_verifier_env *env, case PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF | MEM_RCU: /* When referenced PTR_TO_BTF_ID is passed to release function, * its fixed offset must be 0. In the other cases, fixed offset - * can be non-zero. This was already checked above. So pass - * fixed_off_ok as true to allow fixed offset for all other - * cases. var_off always must be 0 for PTR_TO_BTF_ID, hence we - * still need to do checks instead of returning. + * can be non-zero unless the caller requires otherwise. + * var_off always must be 0 for PTR_TO_BTF_ID, hence we still + * need to do checks instead of returning. */ - return __check_ptr_off_reg(env, reg, argno, true); + return __check_ptr_off_reg(env, reg, argno, btf_id_fixed_off_ok); case PTR_TO_CTX: /* * Allow fixed and variable offsets for syscall context, but @@ -8070,6 +8070,13 @@ static int check_func_arg_reg_off(struct bpf_verifier_env *env, } } +static int check_func_arg_reg_off(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, argno_t argno, + enum bpf_arg_type arg_type) +{ + return __check_func_arg_reg_off(env, reg, argno, arg_type, true); +} + static int check_arg_const_str(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno) { @@ -11941,6 +11948,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ enum bpf_arg_type arg_type = ARG_DONTCARE; argno_t argno = argno_from_arg(i + 1); int regno = reg_from_argno(argno); + bool btf_id_fixed_off_ok = true; u32 ref_id, type_size; bool is_ret_buf_sz = false; int kf_arg_type; @@ -12114,7 +12122,6 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ case KF_ARG_PTR_TO_MEM: case KF_ARG_PTR_TO_MEM_SIZE: case KF_ARG_PTR_TO_CALLBACK: - case KF_ARG_PTR_TO_REFCOUNTED_KPTR: case KF_ARG_PTR_TO_CONST_STR: case KF_ARG_PTR_TO_WORKQUEUE: case KF_ARG_PTR_TO_TIMER: @@ -12128,6 +12135,10 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ case KF_ARG_PTR_TO_CTX: arg_type = ARG_PTR_TO_CTX; break; + case KF_ARG_PTR_TO_REFCOUNTED_KPTR: + arg_type = ARG_PTR_TO_BTF_ID; + btf_id_fixed_off_ok = false; + break; default: verifier_bug(env, "unknown kfunc arg type %d", kf_arg_type); return -EFAULT; @@ -12135,7 +12146,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ if (regno == meta->release_regno) arg_type |= OBJ_RELEASE; - ret = check_func_arg_reg_off(env, reg, argno, arg_type); + ret = __check_func_arg_reg_off(env, reg, argno, arg_type, + btf_id_fixed_off_ok); if (ret < 0) return ret; -- 2.34.1