Commit 0a09a2f9 authored by Kumar Kartikeya Dwivedi's avatar Kumar Kartikeya Dwivedi Committed by Alexei Starovoitov

bpf: Annotate data races in bpf_local_storage

There are a few cases where hlist_node is checked to be unhashed without
holding the lock protecting its modification. In this case, one must use
hlist_unhashed_lockless to avoid load tearing and KCSAN reports. Fix
this by using lockless variant in places not protected by the lock.

Since this is not prompted by any actual KCSAN reports but only from
code review, I have not included a fixes tag.

Cc: Martin KaFai Lau <martin.lau@kernel.org>
Cc: KP Singh <kpsingh@kernel.org>
Signed-off-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230221200646.2500777-4-memxor@gmail.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent bf9bec4c
......@@ -51,11 +51,21 @@ owner_storage(struct bpf_local_storage_map *smap, void *owner)
return map->ops->map_owner_storage_ptr(owner);
}
static bool selem_linked_to_storage_lockless(const struct bpf_local_storage_elem *selem)
{
return !hlist_unhashed_lockless(&selem->snode);
}
static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem)
{
return !hlist_unhashed(&selem->snode);
}
static bool selem_linked_to_map_lockless(const struct bpf_local_storage_elem *selem)
{
return !hlist_unhashed_lockless(&selem->map_node);
}
static bool selem_linked_to_map(const struct bpf_local_storage_elem *selem)
{
return !hlist_unhashed(&selem->map_node);
......@@ -174,7 +184,7 @@ static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
bool free_local_storage = false;
unsigned long flags;
if (unlikely(!selem_linked_to_storage(selem)))
if (unlikely(!selem_linked_to_storage_lockless(selem)))
/* selem has already been unlinked from sk */
return;
......@@ -208,7 +218,7 @@ void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
struct bpf_local_storage_map_bucket *b;
unsigned long flags;
if (unlikely(!selem_linked_to_map(selem)))
if (unlikely(!selem_linked_to_map_lockless(selem)))
/* selem has already be unlinked from smap */
return;
......@@ -420,7 +430,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
err = check_flags(old_sdata, map_flags);
if (err)
return ERR_PTR(err);
if (old_sdata && selem_linked_to_storage(SELEM(old_sdata))) {
if (old_sdata && selem_linked_to_storage_lockless(SELEM(old_sdata))) {
copy_map_value_locked(&smap->map, old_sdata->data,
value, false);
return old_sdata;
......
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