diff mbox series

[v2,bpf-next,2/4] bpf: Make bpf inode storage available to tracing program

Message ID 20241112083700.356299-3-song@kernel.org (mailing list archive)
State New
Headers show
Series Make inode storage available to tracing prog | expand

Commit Message

Song Liu Nov. 12, 2024, 8:36 a.m. UTC 
inode storage can be useful for non-LSM program. For example, file* tools
from bcc/libbpf-tools can use inode storage instead of hash map; fanotify
fastpath [1] can also use inode storage to store useful data.

Make inode storage available for tracing program. Move bpf inode storage
from a security blob to inode->i_bpf_storage, and adjust related code
accordingly.

[1] https://lore.kernel.org/linux-fsdevel/20241029231244.2834368-1-song@kernel.org/
Signed-off-by: Song Liu <song@kernel.org>
---
 fs/inode.c                     |  1 +
 include/linux/bpf.h            |  9 +++++++++
 include/linux/bpf_lsm.h        | 29 -----------------------------
 include/linux/fs.h             |  4 ++++
 kernel/bpf/Makefile            |  3 +--
 kernel/bpf/bpf_inode_storage.c | 32 +++++---------------------------
 kernel/bpf/bpf_lsm.c           |  4 ----
 kernel/trace/bpf_trace.c       |  4 ++++
 security/bpf/hooks.c           |  6 ------
 9 files changed, 24 insertions(+), 68 deletions(-)

Comments

Alexei Starovoitov Nov. 12, 2024, 10:04 p.m. UTC | #1 
On Tue, Nov 12, 2024 at 12:37 AM Song Liu <song@kernel.org> wrote:
>
> inode storage can be useful for non-LSM program. For example, file* tools
> from bcc/libbpf-tools can use inode storage instead of hash map; fanotify
> fastpath [1] can also use inode storage to store useful data.
>
> Make inode storage available for tracing program. Move bpf inode storage
> from a security blob to inode->i_bpf_storage, and adjust related code
> accordingly.

...

> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 3559446279c1..479097e4dd5b 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -79,6 +79,7 @@ struct fs_context;
>  struct fs_parameter_spec;
>  struct fileattr;
>  struct iomap_ops;
> +struct bpf_local_storage;
>
>  extern void __init inode_init(void);
>  extern void __init inode_init_early(void);
> @@ -648,6 +649,9 @@ struct inode {
>  #ifdef CONFIG_SECURITY
>         void                    *i_security;
>  #endif
> +#ifdef CONFIG_BPF_SYSCALL
> +       struct bpf_local_storage __rcu *i_bpf_storage;
> +#endif
>

This bit needs an ack from vfs folks.
Martin KaFai Lau Nov. 12, 2024, 11 p.m. UTC | #2 
On 11/12/24 12:36 AM, Song Liu wrote:
>   void __destroy_inode(struct inode *inode)
>   {
>   	BUG_ON(inode_has_buffers(inode));
> +	bpf_inode_storage_free(inode);

Not sure if this is done in the rcu callback (i.e. after the rcu gp). Please check.

>   	inode_detach_wb(inode);
>   	security_inode_free(inode);
>   	fsnotify_inode_delete(inode);

[ ... ]

> @@ -136,12 +119,7 @@ BPF_CALL_5(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode,
>   	if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
>   		return (unsigned long)NULL;
>   
> -	/* explicitly check that the inode_storage_ptr is not
> -	 * NULL as inode_storage_lookup returns NULL in this case and
> -	 * bpf_local_storage_update expects the owner to have a
> -	 * valid storage pointer.
> -	 */
> -	if (!inode || !inode_storage_ptr(inode))
> +	if (!inode)
>   		return (unsigned long)NULL;

There is an atomic_read in this function:

	/* only allocate new storage, when the inode is refcounted */
	if (atomic_read(&inode->i_count) &&
	    flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {

If the bpf_inode_storage_free is not done after rcu gp, this will need a 
inc_not_zero like how the sk storage does. I think moving the storage_free to 
the inode rcu call back may be easier if it is not the case now.
Song Liu Nov. 12, 2024, 11:10 p.m. UTC | #3 
On Tue, Nov 12, 2024 at 3:00 PM Martin KaFai Lau <martin.lau@linux.dev> wrote:
>
> On 11/12/24 12:36 AM, Song Liu wrote:
> >   void __destroy_inode(struct inode *inode)
> >   {
> >       BUG_ON(inode_has_buffers(inode));
> > +     bpf_inode_storage_free(inode);
>
> Not sure if this is done in the rcu callback (i.e. after the rcu gp). Please check.
>
> >       inode_detach_wb(inode);
> >       security_inode_free(inode);
> >       fsnotify_inode_delete(inode);
>
> [ ... ]
>
> > @@ -136,12 +119,7 @@ BPF_CALL_5(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode,
> >       if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
> >               return (unsigned long)NULL;
> >
> > -     /* explicitly check that the inode_storage_ptr is not
> > -      * NULL as inode_storage_lookup returns NULL in this case and
> > -      * bpf_local_storage_update expects the owner to have a
> > -      * valid storage pointer.
> > -      */
> > -     if (!inode || !inode_storage_ptr(inode))
> > +     if (!inode)
> >               return (unsigned long)NULL;
>
> There is an atomic_read in this function:
>
>         /* only allocate new storage, when the inode is refcounted */
>         if (atomic_read(&inode->i_count) &&
>             flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
>
> If the bpf_inode_storage_free is not done after rcu gp, this will need a
> inc_not_zero like how the sk storage does. I think moving the storage_free to
> the inode rcu call back may be easier if it is not the case now.

This is a great catch!

I will move bpf_inode_storage_free to i_callback().

Thanks,
Song
diff mbox series

Patch

diff --git a/fs/inode.c b/fs/inode.c
index 8dabb224f941..3c679578169f 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -286,6 +286,7 @@  static struct inode *alloc_inode(struct super_block *sb)
 void __destroy_inode(struct inode *inode)
 {
 	BUG_ON(inode_has_buffers(inode));
+	bpf_inode_storage_free(inode);
 	inode_detach_wb(inode);
 	security_inode_free(inode);
 	fsnotify_inode_delete(inode);
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7da41ae2eac8..9da120140327 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2672,6 +2672,7 @@  struct bpf_link *bpf_link_by_id(u32 id);
 const struct bpf_func_proto *bpf_base_func_proto(enum bpf_func_id func_id,
 						 const struct bpf_prog *prog);
 void bpf_task_storage_free(struct task_struct *task);
+void bpf_inode_storage_free(struct inode *inode);
 void bpf_cgrp_storage_free(struct cgroup *cgroup);
 bool bpf_prog_has_kfunc_call(const struct bpf_prog *prog);
 const struct btf_func_model *
@@ -2942,6 +2943,10 @@  static inline void bpf_task_storage_free(struct task_struct *task)
 {
 }
 
+static inline void bpf_inode_storage_free(struct inode *inode)
+{
+}
+
 static inline bool bpf_prog_has_kfunc_call(const struct bpf_prog *prog)
 {
 	return false;
@@ -3305,6 +3310,10 @@  extern const struct bpf_func_proto bpf_task_storage_get_recur_proto;
 extern const struct bpf_func_proto bpf_task_storage_get_proto;
 extern const struct bpf_func_proto bpf_task_storage_delete_recur_proto;
 extern const struct bpf_func_proto bpf_task_storage_delete_proto;
+extern const struct bpf_func_proto bpf_inode_storage_get_proto;
+extern const struct bpf_func_proto bpf_inode_storage_get_recur_proto;
+extern const struct bpf_func_proto bpf_inode_storage_delete_proto;
+extern const struct bpf_func_proto bpf_inode_storage_delete_recur_proto;
 extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
 extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
 extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h
index aefcd6564251..a819c2f0a062 100644
--- a/include/linux/bpf_lsm.h
+++ b/include/linux/bpf_lsm.h
@@ -19,31 +19,12 @@ 
 #include <linux/lsm_hook_defs.h>
 #undef LSM_HOOK
 
-struct bpf_storage_blob {
-	struct bpf_local_storage __rcu *storage;
-};
-
-extern struct lsm_blob_sizes bpf_lsm_blob_sizes;
-
 int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
 			const struct bpf_prog *prog);
 
 bool bpf_lsm_is_sleepable_hook(u32 btf_id);
 bool bpf_lsm_is_trusted(const struct bpf_prog *prog);
 
-static inline struct bpf_storage_blob *bpf_inode(
-	const struct inode *inode)
-{
-	if (unlikely(!inode->i_security))
-		return NULL;
-
-	return inode->i_security + bpf_lsm_blob_sizes.lbs_inode;
-}
-
-extern const struct bpf_func_proto bpf_inode_storage_get_proto;
-extern const struct bpf_func_proto bpf_inode_storage_delete_proto;
-void bpf_inode_storage_free(struct inode *inode);
-
 void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, bpf_func_t *bpf_func);
 
 int bpf_lsm_get_retval_range(const struct bpf_prog *prog,
@@ -66,16 +47,6 @@  static inline int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
 	return -EOPNOTSUPP;
 }
 
-static inline struct bpf_storage_blob *bpf_inode(
-	const struct inode *inode)
-{
-	return NULL;
-}
-
-static inline void bpf_inode_storage_free(struct inode *inode)
-{
-}
-
 static inline void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog,
 					   bpf_func_t *bpf_func)
 {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3559446279c1..479097e4dd5b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -79,6 +79,7 @@  struct fs_context;
 struct fs_parameter_spec;
 struct fileattr;
 struct iomap_ops;
+struct bpf_local_storage;
 
 extern void __init inode_init(void);
 extern void __init inode_init_early(void);
@@ -648,6 +649,9 @@  struct inode {
 #ifdef CONFIG_SECURITY
 	void			*i_security;
 #endif
+#ifdef CONFIG_BPF_SYSCALL
+	struct bpf_local_storage __rcu *i_bpf_storage;
+#endif
 
 	/* Stat data, not accessed from path walking */
 	unsigned long		i_ino;
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 105328f0b9c0..73604c7130f1 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -10,8 +10,7 @@  obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o log.o
 obj-$(CONFIG_BPF_SYSCALL) += bpf_iter.o map_iter.o task_iter.o prog_iter.o link_iter.o
 obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o bloom_filter.o
 obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
-obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o bpf_task_storage.o
-obj-${CONFIG_BPF_LSM}	  += bpf_inode_storage.o
+obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o bpf_task_storage.o bpf_inode_storage.o
 obj-$(CONFIG_BPF_SYSCALL) += disasm.o mprog.o
 obj-$(CONFIG_BPF_JIT) += trampoline.o
 obj-$(CONFIG_BPF_SYSCALL) += btf.o memalloc.o
diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c
index 44ccebc745e5..8d5a9bfe6643 100644
--- a/kernel/bpf/bpf_inode_storage.c
+++ b/kernel/bpf/bpf_inode_storage.c
@@ -21,16 +21,11 @@ 
 
 DEFINE_BPF_STORAGE_CACHE(inode_cache);
 
-static struct bpf_local_storage __rcu **
-inode_storage_ptr(void *owner)
+static struct bpf_local_storage __rcu **inode_storage_ptr(void *owner)
 {
 	struct inode *inode = owner;
-	struct bpf_storage_blob *bsb;
 
-	bsb = bpf_inode(inode);
-	if (!bsb)
-		return NULL;
-	return &bsb->storage;
+	return &inode->i_bpf_storage;
 }
 
 static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode,
@@ -39,14 +34,9 @@  static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode,
 {
 	struct bpf_local_storage *inode_storage;
 	struct bpf_local_storage_map *smap;
-	struct bpf_storage_blob *bsb;
-
-	bsb = bpf_inode(inode);
-	if (!bsb)
-		return NULL;
 
 	inode_storage =
-		rcu_dereference_check(bsb->storage, bpf_rcu_lock_held());
+		rcu_dereference_check(inode->i_bpf_storage, bpf_rcu_lock_held());
 	if (!inode_storage)
 		return NULL;
 
@@ -57,15 +47,10 @@  static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode,
 void bpf_inode_storage_free(struct inode *inode)
 {
 	struct bpf_local_storage *local_storage;
-	struct bpf_storage_blob *bsb;
-
-	bsb = bpf_inode(inode);
-	if (!bsb)
-		return;
 
 	rcu_read_lock();
 
-	local_storage = rcu_dereference(bsb->storage);
+	local_storage = rcu_dereference(inode->i_bpf_storage);
 	if (!local_storage) {
 		rcu_read_unlock();
 		return;
@@ -95,8 +80,6 @@  static long bpf_fd_inode_storage_update_elem(struct bpf_map *map, void *key,
 
 	if (fd_empty(f))
 		return -EBADF;
-	if (!inode_storage_ptr(file_inode(fd_file(f))))
-		return -EBADF;
 
 	sdata = bpf_local_storage_update(file_inode(fd_file(f)),
 					 (struct bpf_local_storage_map *)map,
@@ -136,12 +119,7 @@  BPF_CALL_5(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode,
 	if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
 		return (unsigned long)NULL;
 
-	/* explicitly check that the inode_storage_ptr is not
-	 * NULL as inode_storage_lookup returns NULL in this case and
-	 * bpf_local_storage_update expects the owner to have a
-	 * valid storage pointer.
-	 */
-	if (!inode || !inode_storage_ptr(inode))
+	if (!inode)
 		return (unsigned long)NULL;
 
 	sdata = inode_storage_lookup(inode, map, true);
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 3bc61628ab25..6b6e0730e515 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -231,10 +231,6 @@  bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	}
 
 	switch (func_id) {
-	case BPF_FUNC_inode_storage_get:
-		return &bpf_inode_storage_get_proto;
-	case BPF_FUNC_inode_storage_delete:
-		return &bpf_inode_storage_delete_proto;
 #ifdef CONFIG_NET
 	case BPF_FUNC_sk_storage_get:
 		return &bpf_sk_storage_get_proto;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 949a3870946c..262bd101ea0b 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1553,6 +1553,10 @@  bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		if (bpf_prog_check_recur(prog))
 			return &bpf_task_storage_delete_recur_proto;
 		return &bpf_task_storage_delete_proto;
+	case BPF_FUNC_inode_storage_get:
+		return &bpf_inode_storage_get_proto;
+	case BPF_FUNC_inode_storage_delete:
+		return &bpf_inode_storage_delete_proto;
 	case BPF_FUNC_for_each_map_elem:
 		return &bpf_for_each_map_elem_proto;
 	case BPF_FUNC_snprintf:
diff --git a/security/bpf/hooks.c b/security/bpf/hooks.c
index db759025abe1..67719a04bb0b 100644
--- a/security/bpf/hooks.c
+++ b/security/bpf/hooks.c
@@ -12,7 +12,6 @@  static struct security_hook_list bpf_lsm_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(NAME, bpf_lsm_##NAME),
 	#include <linux/lsm_hook_defs.h>
 	#undef LSM_HOOK
-	LSM_HOOK_INIT(inode_free_security, bpf_inode_storage_free),
 };
 
 static const struct lsm_id bpf_lsmid = {
@@ -28,12 +27,7 @@  static int __init bpf_lsm_init(void)
 	return 0;
 }
 
-struct lsm_blob_sizes bpf_lsm_blob_sizes __ro_after_init = {
-	.lbs_inode = sizeof(struct bpf_storage_blob),
-};
-
 DEFINE_LSM(bpf) = {
 	.name = "bpf",
 	.init = bpf_lsm_init,
-	.blobs = &bpf_lsm_blob_sizes
 };