From: Joanne Koong <joannelkoong@gmail.com>
Date: Thu, 17 Mar 2022 21:55:52 -0700
Subject: bpf: Enable non-atomic allocations in local storage
Patch-mainline: v5.18-rc1
Git-commit: b00fa38a9c1cba044a32a601b49a55a18ed719d1
References: jsc#PED-1377
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
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
include/linux/bpf_local_storage.h | 7 ++--
kernel/bpf/bpf_inode_storage.c | 9 +++--
kernel/bpf/bpf_local_storage.c | 58 ++++++++++++++++++++++++--------------
kernel/bpf/bpf_task_storage.c | 10 +++---
kernel/bpf/verifier.c | 20 +++++++++++++
net/core/bpf_sk_storage.c | 21 +++++++------
6 files changed, 84 insertions(+), 41 deletions(-)
--- a/include/linux/bpf_local_storage.h
+++ b/include/linux/bpf_local_storage.h
@@ -154,16 +154,17 @@ void bpf_selem_unlink_map(struct bpf_loc
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);
--- a/kernel/bpf/bpf_inode_storage.c
+++ b/kernel/bpf/bpf_inode_storage.c
@@ -136,7 +136,7 @@ static int bpf_fd_inode_storage_update_e
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_e
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
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;
}
--- 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 st
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
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_
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, st
!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, st
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, st
}
}
+ 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, st
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);
}
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -174,7 +174,8 @@ static int bpf_pid_task_storage_update_e
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
(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();
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13492,6 +13492,26 @@ static int do_misc_fixups(struct bpf_ver
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.
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -141,7 +141,7 @@ static int bpf_fd_sk_storage_update_elem
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 *n
{
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 so
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 bp
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_allow
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,