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authorTonghao Zhang <tong@infragraf.org>2023-01-11 17:29:01 +0800
committerMartin KaFai Lau <martin.lau@kernel.org>2023-01-12 18:55:42 -0800
commit9f907439dc80e4a2fcfb949927b36c036468dbb3 (patch)
tree7e06977ae0a62da945925ec8b49a579864fdeb54 /kernel
parente7895f017b79410bf4591396a733b876dc1e0e9d (diff)
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bpf: hash map, avoid deadlock with suitable hash mask
The deadlock still may occur while accessed in NMI and non-NMI context. Because in NMI, we still may access the same bucket but with different map_locked index. For example, on the same CPU, .max_entries = 2, we update the hash map, with key = 4, while running bpf prog in NMI nmi_handle(), to update hash map with key = 20, so it will have the same bucket index but have different map_locked index. To fix this issue, using min mask to hash again. Fixes: 20b6cc34ea74 ("bpf: Avoid hashtab deadlock with map_locked") Signed-off-by: Tonghao Zhang <tong@infragraf.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Martin KaFai Lau <martin.lau@linux.dev> Cc: Song Liu <song@kernel.org> Cc: Yonghong Song <yhs@fb.com> Cc: John Fastabend <john.fastabend@gmail.com> Cc: KP Singh <kpsingh@kernel.org> Cc: Stanislav Fomichev <sdf@google.com> Cc: Hao Luo <haoluo@google.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Hou Tao <houtao1@huawei.com> Acked-by: Yonghong Song <yhs@fb.com> Acked-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20230111092903.92389-1-tong@infragraf.org Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/hashtab.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 5aa2b5525f79..66bded144377 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -152,7 +152,7 @@ static inline int htab_lock_bucket(const struct bpf_htab *htab,
{
unsigned long flags;
- hash = hash & HASHTAB_MAP_LOCK_MASK;
+ hash = hash & min_t(u32, HASHTAB_MAP_LOCK_MASK, htab->n_buckets - 1);
preempt_disable();
if (unlikely(__this_cpu_inc_return(*(htab->map_locked[hash])) != 1)) {
@@ -171,7 +171,7 @@ static inline void htab_unlock_bucket(const struct bpf_htab *htab,
struct bucket *b, u32 hash,
unsigned long flags)
{
- hash = hash & HASHTAB_MAP_LOCK_MASK;
+ hash = hash & min_t(u32, HASHTAB_MAP_LOCK_MASK, htab->n_buckets - 1);
raw_spin_unlock_irqrestore(&b->raw_lock, flags);
__this_cpu_dec(*(htab->map_locked[hash]));
preempt_enable();