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 315CE46D0BD; Thu, 20 Aug 2026 16:28:23 +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=1787243304; cv=none; b=jDOc+zWbwpdsGMq0nUbnbJ7p3t85zy/vk0fUL832Uaz3XgHGA9yD0tBdKnyn/3Q8twzlpukTqmNlD0RShylYAAsTY7SmyPJ3uTLnK7D02pOmcpHu8O3vk88oOWXaYIw0CZgv6WEqTfK1F83cwjLhssQ2nugl96m7MQHMaQycu6U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787243304; c=relaxed/simple; bh=vwu/PscxGK7dKNVSfMLqy3X51FcELdj67f9JDGs7Qs0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NmavtuyEC/nXJPJCMXCLfE3Y5GfDoE6g7mAF1tK8aqDvFWC4HkfEvHUJKCxQYf98hQBg4sNTkXKlPMlcJZgHYz3UMWkV5OPOMjMF4wBXOuAukMN+Bmt5Vd5JeGtZRYPMpU1zzr7oCLbj11126N41fpQxIErhK3iVU7yAVtGmS5o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=d7czhjB/; 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="d7czhjB/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93BB51F000E9; Thu, 20 Aug 2026 16:28:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787243303; bh=QLCYyotljJ7cbA6s9wbW7BmI45XujGmqPXTaGYdw50I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=d7czhjB/MiKdDbzpP3/odarURO/PXEQqbNavdzTwlKUQuA/rRWR8Xi4r4a697Cpsc 9Dyyickfj0UQu2NN8EKAboM1SdRSJGatJbFCFoUUYt6UCq1pZqRxzpTOXv0WPqt/Ep FtU3I2TUUMHtTygCtBr2LsgQM0HGpoTGWAy3UyKc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, oxsignal , Matt Bobrowski , Daniel Borkmann , Emil Tsalapatis , Amery Hung , Sasha Levin Subject: [PATCH 5.15 049/272] bpf: Reject BPF_MAP_TYPE_INODE_STORAGE creation if BPF LSM is uninitialized Date: Thu, 20 Aug 2026 16:53:53 +0200 Message-ID: <20260820145232.692161010@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260820145231.229664293@linuxfoundation.org> References: <20260820145231.229664293@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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ 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 Signed-off-by: Greg Kroah-Hartman --- include/linux/bpf_lsm.h | 4 ++++ kernel/bpf/bpf_inode_storage.c | 10 ++++++++++ security/bpf/hooks.c | 3 +++ 3 files changed, 17 insertions(+) --- 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 @@ -44,6 +46,8 @@ void bpf_inode_storage_free(struct inode #else /* !CONFIG_BPF_LSM */ +#define bpf_lsm_initialized false + static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id) { return false; --- a/kernel/bpf/bpf_inode_storage.c +++ b/kernel/bpf/bpf_inode_storage.c @@ -223,6 +223,16 @@ static struct bpf_map *inode_storage_map { struct bpf_local_storage_map *smap; + /* + * 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); + smap = bpf_local_storage_map_alloc(attr); if (IS_ERR(smap)) return ERR_CAST(smap); --- 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[] __lsm_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 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; }