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 63BE9332EBC for ; Tue, 21 Jul 2026 15:48:31 +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=1784648912; cv=none; b=b0vq3ejhFPidpbJw36nrjcJz1XEl+WDjSYX6WerYIPBX/R4vFkQSlygo/CriKPMhdxbYREqTFjlj015y/+nsXf2JCyjDD+m3IUOrgkyspInzkoXDhylE6Mz7n3s5gCy1ZOiDtve25UuI6u14DhgrlJ3TRBIz8jWDy5ORG5XNn24= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784648912; c=relaxed/simple; bh=2/6udh8gLAXjyjpj3oV4TFGRbR5TrDfZYYu1Dpzcak0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mbJuZ3feGbGMp1QGICvs6zqmtMGOMVjwZNSoRV/7tvmNtFxj/OgNCVepV8EIxvdbYpxHbgZyMCL6n5v36o7qBXa8iGN90gnJ/VZPMipFYb/6sv6wSsXCK+GOM8Zy7x821vivUdnf4gnrrbPwUHplnjn+zkLy2x2OpOGpmSI3aZ8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XpX5bWAE; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XpX5bWAE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56A6F1F00A3E; Tue, 21 Jul 2026 15:48:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784648911; bh=QZT1Fyd+Xh7G9V+6aVLKdnPWffkuxGqMMm5F3KEYxGE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XpX5bWAEWXbGmz0c2aNXq4lXQClVbq87J8/snX7yqixOyC++1iW6NTBzp5l5a8yFa kLi9EDzkpczCT9G8ovYly1nDZV/Pf6uIYJykvMSu+53U/Rrr0zhgk0+gPBtseGw70o E1wjCUf4qzKFU9uZxrTM4SK38XZj53PZ+L2w4MyDLsbeShFZCb3Yfmu0uWBUnQcxw5 JJM0iLJtjvEgWPONgWUbc7VJHj58uavvzU8rA8LH5+xTa2MxdUoLs/yhPJ6W2JqrQq CbF5gGcWMe/60hhT6lcfQw3z8ZhpyZjZ6ezPCn1Xkak5He82GqrPSN0jcjokCQk62y rFO4r0kTD/cCA== From: Sasha Levin To: stable@vger.kernel.org Cc: Matt Bobrowski , oxsignal , Daniel Borkmann , Emil Tsalapatis , Amery Hung , Sasha Levin Subject: [PATCH 6.6.y] bpf: Reject BPF_MAP_TYPE_INODE_STORAGE creation if BPF LSM is uninitialized Date: Tue, 21 Jul 2026 11:48:28 -0400 Message-ID: <20260721154828.4004522-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026071659-phobia-custard-5548@gregkh> References: <2026071659-phobia-custard-5548@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Matt Bobrowski [ Upstream commit a6f0643e4f63cfaa0d5d4a69de4f132eac4b8fe4 ] When CONFIG_BPF_LSM=y is set, BPF inode storage maps (BPF_MAP_TYPE_INODE_STORAGE) are compiled into the kernel. However, if the BPF LSM is not explicitly enabled at boot time (e.g. omitted from the "lsm=" boot parameter), lsm_prepare() is never executed for the BPF LSM. Consequently, the BPF inode security blob offset (bpf_lsm_blob_sizes.lbs_inode) is never initialized and remains at its default compiled size of 8 bytes instead of being updated to a valid offset past the reserved struct rcu_head (typically 16 bytes or more). When a privileged user creates and updates a BPF_MAP_TYPE_INODE_STORAGE map, bpf_inode() evaluates inode->i_security + 8. This erroneously aliases the struct rcu_head.func callback pointer at the beginning of the inode->i_security blob. During subsequent map element cleanup or inode destruction, writing NULL to owner_storage clears the queued RCU callback pointer. When rcu_do_batch() later executes the queued callback, it attempts an instruction fetch at address 0x0, triggering an immediate kernel panic. Fix this by introducing a global bpf_lsm_initialized boolean flag marked with __ro_after_init. Set this flag to true inside bpf_lsm_init() when the LSM framework successfully registers the BPF LSM. Gate map allocation in inode_storage_map_alloc() on this flag, returning -EOPNOTSUPP if the BPF LSM is in turn uninitialized. This fail-fast approach prevents userspace from allocating inode storage maps when the supporting BPF LSM infrastructure is absent, avoiding zombie map states. Fixes: 8ea636848aca ("bpf: Implement bpf_local_storage for inodes") Reported-by: oxsignal Signed-off-by: Matt Bobrowski Signed-off-by: Daniel Borkmann Reviewed-by: Emil Tsalapatis Reviewed-by: Amery Hung Link: https://lore.kernel.org/bpf/20260628201103.3624525-1-mattbobrowski@google.com Signed-off-by: Sasha Levin --- include/linux/bpf_lsm.h | 4 ++++ kernel/bpf/bpf_inode_storage.c | 9 +++++++++ security/bpf/hooks.c | 3 +++ 3 files changed, 16 insertions(+) diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h index 1de7ece5d36d43..4f962dccc6c500 100644 --- a/include/linux/bpf_lsm.h +++ b/include/linux/bpf_lsm.h @@ -13,6 +13,8 @@ #ifdef CONFIG_BPF_LSM +extern bool bpf_lsm_initialized __ro_after_init; + #define LSM_HOOK(RET, DEFAULT, NAME, ...) \ RET bpf_lsm_##NAME(__VA_ARGS__); #include @@ -47,6 +49,8 @@ void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, bpf_func_t *bpf_func) #else /* !CONFIG_BPF_LSM */ +#define bpf_lsm_initialized false + static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id) { return false; diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c index b0ef45db207c89..288d776f2d4872 100644 --- a/kernel/bpf/bpf_inode_storage.c +++ b/kernel/bpf/bpf_inode_storage.c @@ -191,6 +191,15 @@ static int notsupp_get_next_key(struct bpf_map *map, void *key, static struct bpf_map *inode_storage_map_alloc(union bpf_attr *attr) { + /* + * Do not allow allocation of BPF_MAP_TYPE_INODE_STORAGE if the BPF LSM + * was not initialized by the LSM framework at boot. Without proper + * initialization, the BPF inode security blob offset remains unprepared, + * causing bpf_inode() to calculate an invalid memory offset and corrupt + * inode->i_security. + */ + if (!bpf_lsm_initialized) + return ERR_PTR(-EOPNOTSUPP); return bpf_local_storage_map_alloc(attr, &inode_cache, false); } diff --git a/security/bpf/hooks.c b/security/bpf/hooks.c index 35933ae53b92cf..2e9c247c3a6327 100644 --- a/security/bpf/hooks.c +++ b/security/bpf/hooks.c @@ -6,6 +6,8 @@ #include #include +bool bpf_lsm_initialized __ro_after_init; + static struct security_hook_list bpf_lsm_hooks[] __ro_after_init = { #define LSM_HOOK(RET, DEFAULT, NAME, ...) \ LSM_HOOK_INIT(NAME, bpf_lsm_##NAME), @@ -18,6 +20,7 @@ static struct security_hook_list bpf_lsm_hooks[] __ro_after_init = { static int __init bpf_lsm_init(void) { security_add_hooks(bpf_lsm_hooks, ARRAY_SIZE(bpf_lsm_hooks), "bpf"); + bpf_lsm_initialized = true; pr_info("LSM support for eBPF active\n"); return 0; } -- 2.53.0