From b00fa38a9c1cba044a32a601b49a55a18ed719d1 Mon Sep 17 00:00:00 2001 From: Joanne Koong Date: Thu, 17 Mar 2022 21:55:52 -0700 Subject: bpf: Enable non-atomic allocations in local storage Currently, local storage memory can only be allocated atomically (GFP_ATOMIC). This restriction is too strict for sleepable bpf programs. In this patch, the verifier detects whether the program is sleepable, and passes the corresponding GFP_KERNEL or GFP_ATOMIC flag as a 5th argument to bpf_task/sk/inode_storage_get. This flag will propagate down to the local storage functions that allocate memory. Please note that bpf_task/sk/inode_storage_update_elem functions are invoked by userspace applications through syscalls. Preemption is disabled before bpf_task/sk/inode_storage_update_elem is called, which means they will always have to allocate memory atomically. Signed-off-by: Joanne Koong Signed-off-by: Alexei Starovoitov Acked-by: KP Singh Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20220318045553.3091807-2-joannekoong@fb.com --- kernel/bpf/bpf_local_storage.c | 58 +++++++++++++++++++++++++++--------------- 1 file changed, 37 insertions(+), 21 deletions(-) (limited to 'kernel/bpf/bpf_local_storage.c') diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index 092a1ac772d7..01aa2b51ec4d 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -63,7 +63,7 @@ static bool selem_linked_to_map(const struct bpf_local_storage_elem *selem) struct bpf_local_storage_elem * bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, - void *value, bool charge_mem) + void *value, bool charge_mem, gfp_t gfp_flags) { struct bpf_local_storage_elem *selem; @@ -71,7 +71,7 @@ bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, return NULL; selem = bpf_map_kzalloc(&smap->map, smap->elem_size, - GFP_ATOMIC | __GFP_NOWARN); + gfp_flags | __GFP_NOWARN); if (selem) { if (value) memcpy(SDATA(selem)->data, value, smap->map.value_size); @@ -282,7 +282,8 @@ static int check_flags(const struct bpf_local_storage_data *old_sdata, int bpf_local_storage_alloc(void *owner, struct bpf_local_storage_map *smap, - struct bpf_local_storage_elem *first_selem) + struct bpf_local_storage_elem *first_selem, + gfp_t gfp_flags) { struct bpf_local_storage *prev_storage, *storage; struct bpf_local_storage **owner_storage_ptr; @@ -293,7 +294,7 @@ int bpf_local_storage_alloc(void *owner, return err; storage = bpf_map_kzalloc(&smap->map, sizeof(*storage), - GFP_ATOMIC | __GFP_NOWARN); + gfp_flags | __GFP_NOWARN); if (!storage) { err = -ENOMEM; goto uncharge; @@ -350,10 +351,10 @@ uncharge: */ struct bpf_local_storage_data * bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, - void *value, u64 map_flags) + void *value, u64 map_flags, gfp_t gfp_flags) { struct bpf_local_storage_data *old_sdata = NULL; - struct bpf_local_storage_elem *selem; + struct bpf_local_storage_elem *selem = NULL; struct bpf_local_storage *local_storage; unsigned long flags; int err; @@ -365,6 +366,9 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, !map_value_has_spin_lock(&smap->map))) return ERR_PTR(-EINVAL); + if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST) + return ERR_PTR(-EINVAL); + local_storage = rcu_dereference_check(*owner_storage(smap, owner), bpf_rcu_lock_held()); if (!local_storage || hlist_empty(&local_storage->list)) { @@ -373,11 +377,11 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, if (err) return ERR_PTR(err); - selem = bpf_selem_alloc(smap, owner, value, true); + selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags); if (!selem) return ERR_PTR(-ENOMEM); - err = bpf_local_storage_alloc(owner, smap, selem); + err = bpf_local_storage_alloc(owner, smap, selem, gfp_flags); if (err) { kfree(selem); mem_uncharge(smap, owner, smap->elem_size); @@ -404,6 +408,12 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, } } + if (gfp_flags == GFP_KERNEL) { + selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags); + if (!selem) + return ERR_PTR(-ENOMEM); + } + raw_spin_lock_irqsave(&local_storage->lock, flags); /* Recheck local_storage->list under local_storage->lock */ @@ -429,19 +439,21 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, goto unlock; } - /* local_storage->lock is held. Hence, we are sure - * we can unlink and uncharge the old_sdata successfully - * later. Hence, instead of charging the new selem now - * and then uncharge the old selem later (which may cause - * a potential but unnecessary charge failure), avoid taking - * a charge at all here (the "!old_sdata" check) and the - * old_sdata will not be uncharged later during - * bpf_selem_unlink_storage_nolock(). - */ - selem = bpf_selem_alloc(smap, owner, value, !old_sdata); - if (!selem) { - err = -ENOMEM; - goto unlock_err; + if (gfp_flags != GFP_KERNEL) { + /* local_storage->lock is held. Hence, we are sure + * we can unlink and uncharge the old_sdata successfully + * later. Hence, instead of charging the new selem now + * and then uncharge the old selem later (which may cause + * a potential but unnecessary charge failure), avoid taking + * a charge at all here (the "!old_sdata" check) and the + * old_sdata will not be uncharged later during + * bpf_selem_unlink_storage_nolock(). + */ + selem = bpf_selem_alloc(smap, owner, value, !old_sdata, gfp_flags); + if (!selem) { + err = -ENOMEM; + goto unlock_err; + } } /* First, link the new selem to the map */ @@ -463,6 +475,10 @@ unlock: unlock_err: raw_spin_unlock_irqrestore(&local_storage->lock, flags); + if (selem) { + mem_uncharge(smap, owner, smap->elem_size); + kfree(selem); + } return ERR_PTR(err); } -- cgit v1.2.3