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bpf: hash map, avoid deadlock with suitable hash mask

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[ Upstream commit 9f907439dc80e4a2fcfb949927b36c036468dbb3 ]

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: 20b6cc34ea ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Tonghao Zhang
2023-01-11 17:29:01 +08:00
committed by Greg Kroah-Hartman
parent 543d66a54d
commit 0a473f8343
1 changed files with 2 additions and 2 deletions
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4
kernel/bpf/hashtab.c
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@@ -163,7 +163,7 @@ static inline int htab_lock_bucket(const struct bpf_htab *htab,
unsigned long flags;
bool use_raw_lock;
hash = hash & HASHTAB_MAP_LOCK_MASK;
hash = hash & min_t(u32, HASHTAB_MAP_LOCK_MASK, htab->n_buckets - 1);
use_raw_lock = htab_use_raw_lock(htab);
if (use_raw_lock)
@@ -194,7 +194,7 @@ static inline void htab_unlock_bucket(const struct bpf_htab *htab,
{
bool use_raw_lock = htab_use_raw_lock(htab);
hash = hash & HASHTAB_MAP_LOCK_MASK;
hash = hash & min_t(u32, HASHTAB_MAP_LOCK_MASK, htab->n_buckets - 1);
if (use_raw_lock)
raw_spin_unlock_irqrestore(&b->raw_lock, flags);
else