diff options
| author |   Alexei Starovoitov <ast@fb.com> | 2017-03-07 20:00:13 -0800 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2017-03-09 13:27:17 -0800 |
| commit | 4fe8435909fddc97b81472026aa954e06dd192a5 (patch) | |
| tree | 31f7007c13a16573229090569e6fc3ca5c496a50 /include/linux/list_nulls.h | |
| parent | bpf: fix struct htab_elem layout (diff) | |
| download | linux-dev-4fe8435909fddc97b81472026aa954e06dd192a5.tar.xz linux-dev-4fe8435909fddc97b81472026aa954e06dd192a5.zip | |
bpf: convert htab map to hlist_nulls
when all map elements are pre-allocated one cpu can delete and reuse htab_elem
while another cpu is still walking the hlist. In such case the lookup may
miss the element. Convert hlist to hlist_nulls to avoid such scenario.
When bucket lock is taken there is no need to take such precautions,
so only convert map_lookup and map_get_next to nulls.
The race window is extremely small and only reproducible with explicit
udelay() inside lookup_nulls_elem_raw()
Similar to hlist add hlist_nulls_for_each_entry_safe() and
hlist_nulls_entry_safe() helpers.
Fixes: 6c9059817432 ("bpf: pre-allocate hash map elements")
Reported-by: Jonathan Perry <jonperry@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/list_nulls.h')
| -rw-r--r-- | include/linux/list_nulls.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h index b01fe1009084..87ff4f58a2f0 100644 --- a/include/linux/list_nulls.h +++ b/include/linux/list_nulls.h @@ -29,6 +29,11 @@ struct hlist_nulls_node { ((ptr)->first = (struct hlist_nulls_node *) NULLS_MARKER(nulls)) #define hlist_nulls_entry(ptr, type, member) container_of(ptr,type,member) + +#define hlist_nulls_entry_safe(ptr, type, member) \ + ({ typeof(ptr) ____ptr = (ptr); \ + !is_a_nulls(____ptr) ? hlist_nulls_entry(____ptr, type, member) : NULL; \ + }) /** * ptr_is_a_nulls - Test if a ptr is a nulls * @ptr: ptr to be tested |