| Message ID | 20211206151909.951258-2-kpsingh@kernel.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | Sleepable local storage | expand |
On Mon, Dec 06, 2021 at 03:19:08PM +0000, KP Singh wrote: > @@ -213,7 +233,8 @@ bpf_local_storage_lookup(struct bpf_local_storage *local_storage, > struct bpf_local_storage_elem *selem; > > /* Fast path (cache hit) */ > - sdata = rcu_dereference(local_storage->cache[smap->cache_idx]); > + sdata = rcu_dereference_check(local_storage->cache[smap->cache_idx], > + bpf_rcu_lock_held()); > if (sdata && rcu_access_pointer(sdata->smap) == smap) > return sdata; In the slow path logic after this, it should need a hlist_for_each_entry_rcu(..., rcu_read_lock_trace_held()) Others lgtm. I will take another fresh look tomorrow. Thanks for the patches !
On Mon, Dec 06, 2021 at 03:19:08PM +0000, KP Singh wrote: [ ... ] > diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c > index 96ceed0e0fb5..20604d904d14 100644 > --- a/kernel/bpf/bpf_inode_storage.c > +++ b/kernel/bpf/bpf_inode_storage.c > @@ -17,6 +17,7 @@ > #include <linux/bpf_lsm.h> > #include <linux/btf_ids.h> > #include <linux/fdtable.h> > +#include <linux/rcupdate_trace.h> > > DEFINE_BPF_STORAGE_CACHE(inode_cache); > > @@ -44,7 +45,8 @@ static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode, > if (!bsb) > return NULL; > > - inode_storage = rcu_dereference(bsb->storage); > + inode_storage = > + rcu_dereference_check(bsb->storage, bpf_rcu_lock_held()); > if (!inode_storage) > return NULL; > > @@ -97,7 +99,8 @@ void bpf_inode_storage_free(struct inode *inode) > * local_storage->list was non-empty. > */ > if (free_inode_storage) > - kfree_rcu(local_storage, rcu); > + call_rcu_tasks_trace(&local_storage->rcu, > + bpf_local_storage_free_rcu); It is not clear to me why bpf_inode_storage_free() needs this change but not in bpf_task_storage_free() and bpf_sk_storage_free(). Could you explain the reason here? > diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c > index bb69aea1a777..1def13ad5c72 100644 > --- a/kernel/bpf/bpf_task_storage.c > +++ b/kernel/bpf/bpf_task_storage.c > @@ -17,6 +17,7 @@ > #include <uapi/linux/btf.h> > #include <linux/btf_ids.h> > #include <linux/fdtable.h> > +#include <linux/rcupdate_trace.h> > > DEFINE_BPF_STORAGE_CACHE(task_cache); > > @@ -59,7 +60,8 @@ task_storage_lookup(struct task_struct *task, struct bpf_map *map, > struct bpf_local_storage *task_storage; > struct bpf_local_storage_map *smap; > > - task_storage = rcu_dereference(task->bpf_storage); > + task_storage = > + rcu_dereference_check(task->bpf_storage, bpf_rcu_lock_held()); > if (!task_storage) > return NULL; > > @@ -77,7 +79,8 @@ void bpf_task_storage_free(struct task_struct *task) > > rcu_read_lock(); > > - local_storage = rcu_dereference(task->bpf_storage); > + local_storage = > + rcu_dereference_check(task->bpf_storage, bpf_rcu_lock_held()); This change is unnecessary. There is a rcu_read_lock() above. > if (!local_storage) { > rcu_read_unlock(); > return;
On Thu, Dec 9, 2021 at 3:00 AM Martin KaFai Lau <kafai@fb.com> wrote: > > On Mon, Dec 06, 2021 at 03:19:08PM +0000, KP Singh wrote: > [ ... ] > > > diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c > > index 96ceed0e0fb5..20604d904d14 100644 > > --- a/kernel/bpf/bpf_inode_storage.c > > +++ b/kernel/bpf/bpf_inode_storage.c > > @@ -17,6 +17,7 @@ > > #include <linux/bpf_lsm.h> > > #include <linux/btf_ids.h> > > #include <linux/fdtable.h> > > +#include <linux/rcupdate_trace.h> > > > > DEFINE_BPF_STORAGE_CACHE(inode_cache); > > > > @@ -44,7 +45,8 @@ static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode, > > if (!bsb) > > return NULL; > > > > - inode_storage = rcu_dereference(bsb->storage); > > + inode_storage = > > + rcu_dereference_check(bsb->storage, bpf_rcu_lock_held()); > > if (!inode_storage) > > return NULL; > > > > @@ -97,7 +99,8 @@ void bpf_inode_storage_free(struct inode *inode) > > * local_storage->list was non-empty. > > */ > > if (free_inode_storage) > > - kfree_rcu(local_storage, rcu); > > + call_rcu_tasks_trace(&local_storage->rcu, > > + bpf_local_storage_free_rcu); > It is not clear to me why bpf_inode_storage_free() needs this change > but not in bpf_task_storage_free() and bpf_sk_storage_free(). > Could you explain the reason here? I think I carried this forward from my older version and messed it up while applying diffs, I tested on the linux-next branch which has it for the other storages as well. We will need to free all these under trace RCU. Will fix it in v3. > > > diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c > > index bb69aea1a777..1def13ad5c72 100644 > > --- a/kernel/bpf/bpf_task_storage.c > > +++ b/kernel/bpf/bpf_task_storage.c > > @@ -17,6 +17,7 @@ > > #include <uapi/linux/btf.h> > > #include <linux/btf_ids.h> > > #include <linux/fdtable.h> > > +#include <linux/rcupdate_trace.h> > > > > DEFINE_BPF_STORAGE_CACHE(task_cache); > > > > @@ -59,7 +60,8 @@ task_storage_lookup(struct task_struct *task, struct bpf_map *map, > > struct bpf_local_storage *task_storage; > > struct bpf_local_storage_map *smap; > > > > - task_storage = rcu_dereference(task->bpf_storage); > > + task_storage = > > + rcu_dereference_check(task->bpf_storage, bpf_rcu_lock_held()); > > if (!task_storage) > > return NULL; > > > > @@ -77,7 +79,8 @@ void bpf_task_storage_free(struct task_struct *task) > > > > rcu_read_lock(); > > > > - local_storage = rcu_dereference(task->bpf_storage); > > + local_storage = > > + rcu_dereference_check(task->bpf_storage, bpf_rcu_lock_held()); > This change is unnecessary. There is a rcu_read_lock() above. Thanks, agreed. > > > if (!local_storage) { > > rcu_read_unlock(); > > return; >
On Thu, Dec 09, 2021 at 03:18:21AM +0100, KP Singh wrote: > On Thu, Dec 9, 2021 at 3:00 AM Martin KaFai Lau <kafai@fb.com> wrote: > > > > On Mon, Dec 06, 2021 at 03:19:08PM +0000, KP Singh wrote: > > [ ... ] > > > > > diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c > > > index 96ceed0e0fb5..20604d904d14 100644 > > > --- a/kernel/bpf/bpf_inode_storage.c > > > +++ b/kernel/bpf/bpf_inode_storage.c > > > @@ -17,6 +17,7 @@ > > > #include <linux/bpf_lsm.h> > > > #include <linux/btf_ids.h> > > > #include <linux/fdtable.h> > > > +#include <linux/rcupdate_trace.h> > > > > > > DEFINE_BPF_STORAGE_CACHE(inode_cache); > > > > > > @@ -44,7 +45,8 @@ static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode, > > > if (!bsb) > > > return NULL; > > > > > > - inode_storage = rcu_dereference(bsb->storage); > > > + inode_storage = > > > + rcu_dereference_check(bsb->storage, bpf_rcu_lock_held()); > > > if (!inode_storage) > > > return NULL; > > > > > > @@ -97,7 +99,8 @@ void bpf_inode_storage_free(struct inode *inode) > > > * local_storage->list was non-empty. > > > */ > > > if (free_inode_storage) > > > - kfree_rcu(local_storage, rcu); > > > + call_rcu_tasks_trace(&local_storage->rcu, > > > + bpf_local_storage_free_rcu); > > It is not clear to me why bpf_inode_storage_free() needs this change > > but not in bpf_task_storage_free() and bpf_sk_storage_free(). > > Could you explain the reason here? > > I think I carried this forward from my older version and messed it up > while applying diffs, I tested on the linux-next branch which has it > for the other storages as well. > > We will need to free all these under trace RCU. Will fix it in v3. For sk, bpf_sk_storage_free() is called when sk is about to be kfree. My understanding is the sleepable bpf_lsm should not be running with this sk in parallel at this point when the sk has already reached the bpf_sk_storage_free(). iow, call_rcu_tasks_trace should not be needed here. The existing kfree_rcu() is for the bpf_local_storage_map_free. I was not sure for inode since the inode's storage life time is not obvious to me, so the earlier question. After another thought, the synchronize_rcu_mult changes in bpf_local_storage_map_free() is also not needed. The first existing synchronize_rcu() is for the bpf_sk_storage_clone(). The second one is for the bpf_(sk|task|inode)_storage_free().
On Wed, Dec 08, 2021 at 11:00:04PM -0800, Martin KaFai Lau wrote: > On Thu, Dec 09, 2021 at 03:18:21AM +0100, KP Singh wrote: > > On Thu, Dec 9, 2021 at 3:00 AM Martin KaFai Lau <kafai@fb.com> wrote: > > > > > > On Mon, Dec 06, 2021 at 03:19:08PM +0000, KP Singh wrote: > > > [ ... ] > > > > > > > diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c > > > > index 96ceed0e0fb5..20604d904d14 100644 > > > > --- a/kernel/bpf/bpf_inode_storage.c > > > > +++ b/kernel/bpf/bpf_inode_storage.c > > > > @@ -17,6 +17,7 @@ > > > > #include <linux/bpf_lsm.h> > > > > #include <linux/btf_ids.h> > > > > #include <linux/fdtable.h> > > > > +#include <linux/rcupdate_trace.h> > > > > > > > > DEFINE_BPF_STORAGE_CACHE(inode_cache); > > > > > > > > @@ -44,7 +45,8 @@ static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode, > > > > if (!bsb) > > > > return NULL; > > > > > > > > - inode_storage = rcu_dereference(bsb->storage); > > > > + inode_storage = > > > > + rcu_dereference_check(bsb->storage, bpf_rcu_lock_held()); > > > > if (!inode_storage) > > > > return NULL; > > > > > > > > @@ -97,7 +99,8 @@ void bpf_inode_storage_free(struct inode *inode) > > > > * local_storage->list was non-empty. > > > > */ > > > > if (free_inode_storage) > > > > - kfree_rcu(local_storage, rcu); > > > > + call_rcu_tasks_trace(&local_storage->rcu, > > > > + bpf_local_storage_free_rcu); > > > It is not clear to me why bpf_inode_storage_free() needs this change > > > but not in bpf_task_storage_free() and bpf_sk_storage_free(). > > > Could you explain the reason here? > > > > I think I carried this forward from my older version and messed it up > > while applying diffs, I tested on the linux-next branch which has it > > for the other storages as well. > > > > We will need to free all these under trace RCU. Will fix it in v3. > For sk, bpf_sk_storage_free() is called when sk is about to be kfree. > My understanding is the sleepable bpf_lsm should not be running > with this sk in parallel at this point when the sk has already reached > the bpf_sk_storage_free(). iow, call_rcu_tasks_trace should not > be needed here. The existing kfree_rcu() is for the > bpf_local_storage_map_free. > > I was not sure for inode since the inode's storage life time > is not obvious to me, so the earlier question. > > After another thought, the synchronize_rcu_mult changes in > bpf_local_storage_map_free() is also not needed. The first > existing synchronize_rcu() is for the bpf_sk_storage_clone(). > The second one is for the bpf_(sk|task|inode)_storage_free(). KP, if the above comment makes sense, do you want to respin v3 ? or I can also help to respin and keep your SOB? Thanks.
On Tue, Dec 21, 2021 at 12:30 AM Martin KaFai Lau <kafai@fb.com> wrote: > > On Wed, Dec 08, 2021 at 11:00:04PM -0800, Martin KaFai Lau wrote: > > On Thu, Dec 09, 2021 at 03:18:21AM +0100, KP Singh wrote: > > > On Thu, Dec 9, 2021 at 3:00 AM Martin KaFai Lau <kafai@fb.com> wrote: > > > > > > > > On Mon, Dec 06, 2021 at 03:19:08PM +0000, KP Singh wrote: > > > > [ ... ] > > > > > > > > > diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c > > > > > index 96ceed0e0fb5..20604d904d14 100644 > > > > > --- a/kernel/bpf/bpf_inode_storage.c > > > > > +++ b/kernel/bpf/bpf_inode_storage.c > > > > > @@ -17,6 +17,7 @@ > > > > > #include <linux/bpf_lsm.h> > > > > > #include <linux/btf_ids.h> > > > > > #include <linux/fdtable.h> > > > > > +#include <linux/rcupdate_trace.h> > > > > > > > > > > DEFINE_BPF_STORAGE_CACHE(inode_cache); > > > > > > > > > > @@ -44,7 +45,8 @@ static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode, > > > > > if (!bsb) > > > > > return NULL; > > > > > > > > > > - inode_storage = rcu_dereference(bsb->storage); > > > > > + inode_storage = > > > > > + rcu_dereference_check(bsb->storage, bpf_rcu_lock_held()); > > > > > if (!inode_storage) > > > > > return NULL; > > > > > > > > > > @@ -97,7 +99,8 @@ void bpf_inode_storage_free(struct inode *inode) > > > > > * local_storage->list was non-empty. > > > > > */ > > > > > if (free_inode_storage) > > > > > - kfree_rcu(local_storage, rcu); > > > > > + call_rcu_tasks_trace(&local_storage->rcu, > > > > > + bpf_local_storage_free_rcu); > > > > It is not clear to me why bpf_inode_storage_free() needs this change > > > > but not in bpf_task_storage_free() and bpf_sk_storage_free(). > > > > Could you explain the reason here? > > > > > > I think I carried this forward from my older version and messed it up > > > while applying diffs, I tested on the linux-next branch which has it > > > for the other storages as well. > > > > > > We will need to free all these under trace RCU. Will fix it in v3. > > For sk, bpf_sk_storage_free() is called when sk is about to be kfree. > > My understanding is the sleepable bpf_lsm should not be running > > with this sk in parallel at this point when the sk has already reached > > the bpf_sk_storage_free(). iow, call_rcu_tasks_trace should not > > be needed here. The existing kfree_rcu() is for the > > bpf_local_storage_map_free. > > > > I was not sure for inode since the inode's storage life time > > is not obvious to me, so the earlier question. > > > > After another thought, the synchronize_rcu_mult changes in > > bpf_local_storage_map_free() is also not needed. The first > > existing synchronize_rcu() is for the bpf_sk_storage_clone(). > > The second one is for the bpf_(sk|task|inode)_storage_free(). > KP, if the above comment makes sense, do you want to respin v3 ? > or I can also help to respin and keep your SOB? Thanks. Hey Martin, the comment makes sense, I just took some time off and traveled to India (which was complicated these days). I can respin it this week.
On Thu, Dec 9, 2021 at 12:30 PM Martin KaFai Lau <kafai@fb.com> wrote: > > On Thu, Dec 09, 2021 at 03:18:21AM +0100, KP Singh wrote: > > On Thu, Dec 9, 2021 at 3:00 AM Martin KaFai Lau <kafai@fb.com> wrote: > > > > > > On Mon, Dec 06, 2021 at 03:19:08PM +0000, KP Singh wrote: > > > [ ... ] > > > > > > > diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c > > > > index 96ceed0e0fb5..20604d904d14 100644 > > > > --- a/kernel/bpf/bpf_inode_storage.c > > > > +++ b/kernel/bpf/bpf_inode_storage.c > > > > @@ -17,6 +17,7 @@ > > > > #include <linux/bpf_lsm.h> > > > > #include <linux/btf_ids.h> > > > > #include <linux/fdtable.h> > > > > +#include <linux/rcupdate_trace.h> > > > > > > > > DEFINE_BPF_STORAGE_CACHE(inode_cache); > > > > > > > > @@ -44,7 +45,8 @@ static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode, > > > > if (!bsb) > > > > return NULL; > > > > > > > > - inode_storage = rcu_dereference(bsb->storage); > > > > + inode_storage = > > > > + rcu_dereference_check(bsb->storage, bpf_rcu_lock_held()); > > > > if (!inode_storage) > > > > return NULL; > > > > > > > > @@ -97,7 +99,8 @@ void bpf_inode_storage_free(struct inode *inode) > > > > * local_storage->list was non-empty. > > > > */ > > > > if (free_inode_storage) > > > > - kfree_rcu(local_storage, rcu); > > > > + call_rcu_tasks_trace(&local_storage->rcu, > > > > + bpf_local_storage_free_rcu); > > > It is not clear to me why bpf_inode_storage_free() needs this change > > > but not in bpf_task_storage_free() and bpf_sk_storage_free(). > > > Could you explain the reason here? > > > > I think I carried this forward from my older version and messed it up > > while applying diffs, I tested on the linux-next branch which has it > > for the other storages as well. > > > > We will need to free all these under trace RCU. Will fix it in v3. > For sk, bpf_sk_storage_free() is called when sk is about to be kfree. > My understanding is the sleepable bpf_lsm should not be running > with this sk in parallel at this point when the sk has already reached > the bpf_sk_storage_free(). iow, call_rcu_tasks_trace should not > be needed here. The existing kfree_rcu() is for the > bpf_local_storage_map_free. > You are right, the callback for both the task and inode are called before the inode is actually freed, [inode_free_security and task_free] This is similar to the lifetime of the sk storage so kfree_rcu should suffice. > I was not sure for inode since the inode's storage life time > is not obvious to me, so the earlier question. > > After another thought, the synchronize_rcu_mult changes in > bpf_local_storage_map_free() is also not needed. The first > existing synchronize_rcu() is for the bpf_sk_storage_clone(). > The second one is for the bpf_(sk|task|inode)_storage_free().
diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h index 24496bc28e7b..475431a36a62 100644 --- a/include/linux/bpf_local_storage.h +++ b/include/linux/bpf_local_storage.h @@ -16,6 +16,9 @@ #define BPF_LOCAL_STORAGE_CACHE_SIZE 16 +#define bpf_rcu_lock_held() \ + (rcu_read_lock_held() || rcu_read_lock_trace_held() || \ + rcu_read_lock_bh_held()) struct bpf_local_storage_map_bucket { struct hlist_head list; raw_spinlock_t lock; @@ -161,4 +164,6 @@ struct bpf_local_storage_data * bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, void *value, u64 map_flags); +void bpf_local_storage_free_rcu(struct rcu_head *rcu); + #endif /* _BPF_LOCAL_STORAGE_H */ diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c index 96ceed0e0fb5..20604d904d14 100644 --- a/kernel/bpf/bpf_inode_storage.c +++ b/kernel/bpf/bpf_inode_storage.c @@ -17,6 +17,7 @@ #include <linux/bpf_lsm.h> #include <linux/btf_ids.h> #include <linux/fdtable.h> +#include <linux/rcupdate_trace.h> DEFINE_BPF_STORAGE_CACHE(inode_cache); @@ -44,7 +45,8 @@ static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode, if (!bsb) return NULL; - inode_storage = rcu_dereference(bsb->storage); + inode_storage = + rcu_dereference_check(bsb->storage, bpf_rcu_lock_held()); if (!inode_storage) return NULL; @@ -97,7 +99,8 @@ void bpf_inode_storage_free(struct inode *inode) * local_storage->list was non-empty. */ if (free_inode_storage) - kfree_rcu(local_storage, rcu); + call_rcu_tasks_trace(&local_storage->rcu, + bpf_local_storage_free_rcu); } static void *bpf_fd_inode_storage_lookup_elem(struct bpf_map *map, void *key) @@ -172,6 +175,7 @@ BPF_CALL_4(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode, { struct bpf_local_storage_data *sdata; + WARN_ON_ONCE(!bpf_rcu_lock_held()); if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE)) return (unsigned long)NULL; @@ -204,6 +208,7 @@ BPF_CALL_4(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode, BPF_CALL_2(bpf_inode_storage_delete, struct bpf_map *, map, struct inode *, inode) { + WARN_ON_ONCE(!bpf_rcu_lock_held()); if (!inode) return -EINVAL; diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index b305270b7a4b..ff65d3711d3a 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -11,6 +11,9 @@ #include <net/sock.h> #include <uapi/linux/sock_diag.h> #include <uapi/linux/btf.h> +#include <linux/rcupdate.h> +#include <linux/rcupdate_trace.h> +#include <linux/rcupdate_wait.h> #define BPF_LOCAL_STORAGE_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_CLONE) @@ -81,6 +84,22 @@ bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, return NULL; } +void bpf_local_storage_free_rcu(struct rcu_head *rcu) +{ + struct bpf_local_storage *local_storage; + + local_storage = container_of(rcu, struct bpf_local_storage, rcu); + kfree_rcu(local_storage, rcu); +} + +static void bpf_selem_free_rcu(struct rcu_head *rcu) +{ + struct bpf_local_storage_elem *selem; + + selem = container_of(rcu, struct bpf_local_storage_elem, rcu); + kfree_rcu(selem, rcu); +} + /* local_storage->lock must be held and selem->local_storage == local_storage. * The caller must ensure selem->smap is still valid to be * dereferenced for its smap->elem_size and smap->cache_idx. @@ -93,7 +112,7 @@ bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage, bool free_local_storage; void *owner; - smap = rcu_dereference(SDATA(selem)->smap); + smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held()); owner = local_storage->owner; /* All uncharging on the owner must be done first. @@ -118,12 +137,12 @@ bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage, * * Although the unlock will be done under * rcu_read_lock(), it is more intutivie to - * read if kfree_rcu(local_storage, rcu) is done + * read if the freeing of the storage is done * after the raw_spin_unlock_bh(&local_storage->lock). * * Hence, a "bool free_local_storage" is returned - * to the caller which then calls the kfree_rcu() - * after unlock. + * to the caller which then calls then frees the storage after + * all the RCU grace periods have expired. */ } hlist_del_init_rcu(&selem->snode); @@ -131,8 +150,7 @@ bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage, SDATA(selem)) RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL); - kfree_rcu(selem, rcu); - + call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu); return free_local_storage; } @@ -146,7 +164,8 @@ static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem) /* selem has already been unlinked from sk */ return; - local_storage = rcu_dereference(selem->local_storage); + local_storage = rcu_dereference_check(selem->local_storage, + bpf_rcu_lock_held()); raw_spin_lock_irqsave(&local_storage->lock, flags); if (likely(selem_linked_to_storage(selem))) free_local_storage = bpf_selem_unlink_storage_nolock( @@ -154,7 +173,8 @@ static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem) raw_spin_unlock_irqrestore(&local_storage->lock, flags); if (free_local_storage) - kfree_rcu(local_storage, rcu); + call_rcu_tasks_trace(&local_storage->rcu, + bpf_local_storage_free_rcu); } void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage, @@ -174,7 +194,7 @@ void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) /* selem has already be unlinked from smap */ return; - smap = rcu_dereference(SDATA(selem)->smap); + smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held()); b = select_bucket(smap, selem); raw_spin_lock_irqsave(&b->lock, flags); if (likely(selem_linked_to_map(selem))) @@ -213,7 +233,8 @@ bpf_local_storage_lookup(struct bpf_local_storage *local_storage, struct bpf_local_storage_elem *selem; /* Fast path (cache hit) */ - sdata = rcu_dereference(local_storage->cache[smap->cache_idx]); + sdata = rcu_dereference_check(local_storage->cache[smap->cache_idx], + bpf_rcu_lock_held()); if (sdata && rcu_access_pointer(sdata->smap) == smap) return sdata; @@ -306,7 +327,8 @@ int bpf_local_storage_alloc(void *owner, * bucket->list, first_selem can be freed immediately * (instead of kfree_rcu) because * bpf_local_storage_map_free() does a - * synchronize_rcu() before walking the bucket->list. + * synchronize_rcu_mult (waiting for both sleepable and + * normal programs) before walking the bucket->list. * Hence, no one is accessing selem from the * bucket->list under rcu_read_lock(). */ @@ -342,7 +364,8 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, !map_value_has_spin_lock(&smap->map))) return ERR_PTR(-EINVAL); - local_storage = rcu_dereference(*owner_storage(smap, owner)); + local_storage = rcu_dereference_check(*owner_storage(smap, owner), + bpf_rcu_lock_held()); if (!local_storage || hlist_empty(&local_storage->list)) { /* Very first elem for the owner */ err = check_flags(NULL, map_flags); @@ -486,7 +509,7 @@ void bpf_local_storage_map_free(struct bpf_local_storage_map *smap, * RCU read section to finish before proceeding. New RCU * read sections should be prevented via bpf_map_inc_not_zero. */ - synchronize_rcu(); + synchronize_rcu_mult(call_rcu, call_rcu_tasks_trace); /* bpf prog and the userspace can no longer access this map * now. No new selem (of this map) can be added @@ -530,7 +553,7 @@ void bpf_local_storage_map_free(struct bpf_local_storage_map *smap, * * Hence, wait another rcu grace period for the storage to be freed. */ - synchronize_rcu(); + synchronize_rcu_mult(call_rcu, call_rcu_tasks_trace); kvfree(smap->buckets); kfree(smap); diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c index bb69aea1a777..1def13ad5c72 100644 --- a/kernel/bpf/bpf_task_storage.c +++ b/kernel/bpf/bpf_task_storage.c @@ -17,6 +17,7 @@ #include <uapi/linux/btf.h> #include <linux/btf_ids.h> #include <linux/fdtable.h> +#include <linux/rcupdate_trace.h> DEFINE_BPF_STORAGE_CACHE(task_cache); @@ -59,7 +60,8 @@ task_storage_lookup(struct task_struct *task, struct bpf_map *map, struct bpf_local_storage *task_storage; struct bpf_local_storage_map *smap; - task_storage = rcu_dereference(task->bpf_storage); + task_storage = + rcu_dereference_check(task->bpf_storage, bpf_rcu_lock_held()); if (!task_storage) return NULL; @@ -77,7 +79,8 @@ void bpf_task_storage_free(struct task_struct *task) rcu_read_lock(); - local_storage = rcu_dereference(task->bpf_storage); + local_storage = + rcu_dereference_check(task->bpf_storage, bpf_rcu_lock_held()); if (!local_storage) { rcu_read_unlock(); return; @@ -229,6 +232,7 @@ BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *, { struct bpf_local_storage_data *sdata; + WARN_ON_ONCE(!bpf_rcu_lock_held()); if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE)) return (unsigned long)NULL; @@ -260,6 +264,7 @@ BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *, { int ret; + WARN_ON_ONCE(!bpf_rcu_lock_held()); if (!task) return -EINVAL; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 1126b75fe650..b6cc8c129579 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11791,6 +11791,9 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env, } break; case BPF_MAP_TYPE_RINGBUF: + case BPF_MAP_TYPE_INODE_STORAGE: + case BPF_MAP_TYPE_SK_STORAGE: + case BPF_MAP_TYPE_TASK_STORAGE: break; default: verbose(env, diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c index 68d2cbf8331a..b6c725f30fd4 100644 --- a/net/core/bpf_sk_storage.c +++ b/net/core/bpf_sk_storage.c @@ -13,6 +13,7 @@ #include <net/sock.h> #include <uapi/linux/sock_diag.h> #include <uapi/linux/btf.h> +#include <linux/rcupdate_trace.h> DEFINE_BPF_STORAGE_CACHE(sk_cache); @@ -22,7 +23,8 @@ bpf_sk_storage_lookup(struct sock *sk, struct bpf_map *map, bool cacheit_lockit) struct bpf_local_storage *sk_storage; struct bpf_local_storage_map *smap; - sk_storage = rcu_dereference(sk->sk_bpf_storage); + sk_storage = + rcu_dereference_check(sk->sk_bpf_storage, bpf_rcu_lock_held()); if (!sk_storage) return NULL; @@ -258,6 +260,7 @@ BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk, { struct bpf_local_storage_data *sdata; + WARN_ON_ONCE(!bpf_rcu_lock_held()); if (!sk || !sk_fullsock(sk) || flags > BPF_SK_STORAGE_GET_F_CREATE) return (unsigned long)NULL; @@ -288,6 +291,7 @@ BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk, BPF_CALL_2(bpf_sk_storage_delete, struct bpf_map *, map, struct sock *, sk) { + WARN_ON_ONCE(!bpf_rcu_lock_held()); if (!sk || !sk_fullsock(sk)) return -EINVAL; @@ -416,6 +420,7 @@ static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog) BPF_CALL_4(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk, void *, value, u64, flags) { + WARN_ON_ONCE(!bpf_rcu_lock_held()); if (in_hardirq() || in_nmi()) return (unsigned long)NULL; @@ -425,6 +430,7 @@ BPF_CALL_4(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk, BPF_CALL_2(bpf_sk_storage_delete_tracing, struct bpf_map *, map, struct sock *, sk) { + WARN_ON_ONCE(!bpf_rcu_lock_held()); if (in_hardirq() || in_nmi()) return -EPERM;
Other maps like hashmaps are already available to sleepable programs. Sleepable BPF programs run under trace RCU. Allow task, sk and inode storage to be used from sleepable programs. This allows sleepable and non-sleepable programs to provide shareable annotations on kernel objects. Sleepable programs run in trace RCU where as non-sleepable programs run in a normal RCU critical section i.e. __bpf_prog_enter{_sleepable} and __bpf_prog_exit{_sleepable}) (rcu_read_lock or rcu_read_lock_trace). In order to make the local storage maps accessible to both sleepable and non-sleepable programs, one needs to call both call_rcu_tasks_trace and call_rcu to wait for both trace and classical RCU grace periods to expire before freeing memory. Paul's work on call_rcu_tasks_trace allows us to have per CPU queueing for call_rcu_tasks_trace. This behaviour can be achieved by setting rcupdate.rcu_task_enqueue_lim=<num_cpus> boot parameter. In light of these new performance changes and to keep the local storage code simple, avoid adding a new flag for sleepable maps / local storage to select the RCU synchronization (trace / classical). Also, update the dereferencing of the pointers to use rcu_derference_check (with either the trace or normal RCU locks held) with a common bpf_rcu_lock_held helper method. Signed-off-by: KP Singh <kpsingh@kernel.org> --- include/linux/bpf_local_storage.h | 5 +++ kernel/bpf/bpf_inode_storage.c | 9 ++++-- kernel/bpf/bpf_local_storage.c | 51 ++++++++++++++++++++++--------- kernel/bpf/bpf_task_storage.c | 9 ++++-- kernel/bpf/verifier.c | 3 ++ net/core/bpf_sk_storage.c | 8 ++++- 6 files changed, 66 insertions(+), 19 deletions(-)