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bpf: Enable non-atomic allocations in local storage

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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 <joannelkoong@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: KP Singh <kpsingh@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220318045553.3091807-2-joannekoong@fb.com
This commit is contained in:
Joanne Koong 2022-03-17 21:55:52 -07:00 committed by Alexei Starovoitov
parent a8fee96202
commit b00fa38a9c
6 changed files with 84 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/bpf_local_storage.h
View File

@ -154,16 +154,17 @@ void bpf_selem_unlink_map(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);
bool charge_mem, gfp_t gfp_flags);
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_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);
void bpf_local_storage_free_rcu(struct rcu_head *rcu);

9
kernel/bpf/bpf_inode_storage.c
View File

@ -136,7 +136,7 @@ static int bpf_fd_inode_storage_update_elem(struct bpf_map *map, void *key,
sdata = bpf_local_storage_update(f->f_inode,
(struct bpf_local_storage_map *)map,
value, map_flags);
value, map_flags, GFP_ATOMIC);
fput(f);
return PTR_ERR_OR_ZERO(sdata);
}
@ -169,8 +169,9 @@ static int bpf_fd_inode_storage_delete_elem(struct bpf_map *map, void *key)
return err;
}
BPF_CALL_4(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode,
void *, value, u64, flags)
/* *gfp_flags* is a hidden argument provided by the verifier */
BPF_CALL_5(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode,
void *, value, u64, flags, gfp_t, gfp_flags)
{
struct bpf_local_storage_data *sdata;
@ -196,7 +197,7 @@ BPF_CALL_4(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode,
if (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
sdata = bpf_local_storage_update(
inode, (struct bpf_local_storage_map *)map, value,
BPF_NOEXIST);
BPF_NOEXIST, gfp_flags);
return IS_ERR(sdata) ? (unsigned long)NULL :
(unsigned long)sdata->data;
}

58
kernel/bpf/bpf_local_storage.c
View File

@ -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);
}

10
kernel/bpf/bpf_task_storage.c
View File

@ -174,7 +174,8 @@ static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
bpf_task_storage_lock();
sdata = bpf_local_storage_update(
task, (struct bpf_local_storage_map *)map, value, map_flags);
task, (struct bpf_local_storage_map *)map, value, map_flags,
GFP_ATOMIC);
bpf_task_storage_unlock();
err = PTR_ERR_OR_ZERO(sdata);
@ -226,8 +227,9 @@ out:
return err;
}
BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
task, void *, value, u64, flags)
/* *gfp_flags* is a hidden argument provided by the verifier */
BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
task, void *, value, u64, flags, gfp_t, gfp_flags)
{
struct bpf_local_storage_data *sdata;
@ -250,7 +252,7 @@ BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
(flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
sdata = bpf_local_storage_update(
task, (struct bpf_local_storage_map *)map, value,
BPF_NOEXIST);
BPF_NOEXIST, gfp_flags);
unlock:
bpf_task_storage_unlock();

20
kernel/bpf/verifier.c
View File

@ -13492,6 +13492,26 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
goto patch_call_imm;
}
if (insn->imm == BPF_FUNC_task_storage_get ||
insn->imm == BPF_FUNC_sk_storage_get ||
insn->imm == BPF_FUNC_inode_storage_get) {
if (env->prog->aux->sleepable)
insn_buf[0] = BPF_MOV64_IMM(BPF_REG_5, (__s32)GFP_KERNEL);
else
insn_buf[0] = BPF_MOV64_IMM(BPF_REG_5, (__s32)GFP_ATOMIC);
insn_buf[1] = *insn;
cnt = 2;
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
env->prog = prog = new_prog;
insn = new_prog->insnsi + i + delta;
goto patch_call_imm;
}
/* BPF_EMIT_CALL() assumptions in some of the map_gen_lookup
* and other inlining handlers are currently limited to 64 bit
* only.

21
net/core/bpf_sk_storage.c
View File

@ -141,7 +141,7 @@ static int bpf_fd_sk_storage_update_elem(struct bpf_map *map, void *key,
if (sock) {
sdata = bpf_local_storage_update(
sock->sk, (struct bpf_local_storage_map *)map, value,
map_flags);
map_flags, GFP_ATOMIC);
sockfd_put(sock);
return PTR_ERR_OR_ZERO(sdata);
}
@ -172,7 +172,7 @@ bpf_sk_storage_clone_elem(struct sock *newsk,
{
struct bpf_local_storage_elem *copy_selem;
copy_selem = bpf_selem_alloc(smap, newsk, NULL, true);
copy_selem = bpf_selem_alloc(smap, newsk, NULL, true, GFP_ATOMIC);
if (!copy_selem)
return NULL;
@ -230,7 +230,7 @@ int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk)
bpf_selem_link_map(smap, copy_selem);
bpf_selem_link_storage_nolock(new_sk_storage, copy_selem);
} else {
ret = bpf_local_storage_alloc(newsk, smap, copy_selem);
ret = bpf_local_storage_alloc(newsk, smap, copy_selem, GFP_ATOMIC);
if (ret) {
kfree(copy_selem);
atomic_sub(smap->elem_size,
@ -255,8 +255,9 @@ out:
return ret;
}
BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk,
void *, value, u64, flags)
/* *gfp_flags* is a hidden argument provided by the verifier */
BPF_CALL_5(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk,
void *, value, u64, flags, gfp_t, gfp_flags)
{
struct bpf_local_storage_data *sdata;
@ -277,7 +278,7 @@ BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk,
refcount_inc_not_zero(&sk->sk_refcnt)) {
sdata = bpf_local_storage_update(
sk, (struct bpf_local_storage_map *)map, value,
BPF_NOEXIST);
BPF_NOEXIST, gfp_flags);
/* sk must be a fullsock (guaranteed by verifier),
* so sock_gen_put() is unnecessary.
*/
@ -417,14 +418,16 @@ static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog)
return false;
}
BPF_CALL_4(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk,
void *, value, u64, flags)
/* *gfp_flags* is a hidden argument provided by the verifier */
BPF_CALL_5(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk,
void *, value, u64, flags, gfp_t, gfp_flags)
{
WARN_ON_ONCE(!bpf_rcu_lock_held());
if (in_hardirq() || in_nmi())
return (unsigned long)NULL;
return (unsigned long)____bpf_sk_storage_get(map, sk, value, flags);
return (unsigned long)____bpf_sk_storage_get(map, sk, value, flags,
gfp_flags);
}
BPF_CALL_2(bpf_sk_storage_delete_tracing, struct bpf_map *, map,