From: Matt Bobrowski <mattbobrowski@google.com> mainline inclusion from mainline-v7.2-rc2 commit a6f0643e4f63cfaa0d5d4a69de4f132eac4b8fe4 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16515 CVE: CVE-2026-64192 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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 <awo@kakao.com> Signed-off-by: Matt Bobrowski <mattbobrowski@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Reviewed-by: Amery Hung <ameryhung@gmail.com> Link: https://lore.kernel.org/bpf/20260628201103.3624525-1-mattbobrowski@google.co... Conflicts: include/linux/bpf_lsm.h kernel/bpf/bpf_inode_storage.c security/bpf/hooks.c [ctx conflicts] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- include/linux/bpf_lsm.h | 4 ++++ kernel/bpf/bpf_inode_storage.c | 10 ++++++++++ security/bpf/hooks.c | 3 +++ 3 files changed, 17 insertions(+) diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h index 272655378f94..4947fc758de8 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 <linux/lsm_hook_defs.h> @@ -44,6 +46,8 @@ int bpf_lsm_get_retval_range(const struct bpf_prog *prog, struct bpf_retval_range *range); #else /* !CONFIG_BPF_LSM */ +#define bpf_lsm_initialized false + static inline int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog, const struct bpf_prog *prog) { diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c index a4ac48c7dada..4fd82425feba 100644 --- 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_alloc(union bpf_attr *attr) { 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); diff --git a/security/bpf/hooks.c b/security/bpf/hooks.c index 788667d582ae..bdda0ca174a9 100644 --- a/security/bpf/hooks.c +++ b/security/bpf/hooks.c @@ -6,6 +6,8 @@ #include <linux/lsm_hooks.h> #include <linux/bpf_lsm.h> +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), @@ -17,6 +19,7 @@ static struct security_hook_list bpf_lsm_hooks[] __lsm_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; } -- 2.34.1