6.12-stable review patch. If anyone has any objections, please let me know.
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From: Herbert Xu herbert@gondor.apana.org.au
[ Upstream commit 9d4f8e54cef2c42e23ef258833dbd06a1eaff89b ]
The test on whether rhashtable_insert_one did an insertion relies on the value returned by rhashtable_lookup_one. Unfortunately that value is overwritten after rhashtable_insert_one returns. Fix this by moving the test before data gets overwritten.
Simplify the test as only data == NULL matters.
Finally move atomic_inc back within the lock as otherwise it may be reordered with the atomic_dec on the removal side, potentially leading to an underflow.
Reported-by: Michael Kelley mhklinux@outlook.com Fixes: e1d3422c95f0 ("rhashtable: Fix potential deadlock by moving schedule_work outside lock") Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Tested-by: Michael Kelley mhklinux@outlook.com Reviewed-by: Breno Leitao leitao@debian.org Tested-by: Mikhail Zaslonko zaslonko@linux.ibm.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Sasha Levin sashal@kernel.org --- lib/rhashtable.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index bf956b85455ab..0e9a1d4cf89be 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -611,21 +611,23 @@ static void *rhashtable_try_insert(struct rhashtable *ht, const void *key, new_tbl = rht_dereference_rcu(tbl->future_tbl, ht); data = ERR_PTR(-EAGAIN); } else { + bool inserted; + flags = rht_lock(tbl, bkt); data = rhashtable_lookup_one(ht, bkt, tbl, hash, key, obj); new_tbl = rhashtable_insert_one(ht, bkt, tbl, hash, obj, data); + inserted = data && !new_tbl; + if (inserted) + atomic_inc(&ht->nelems); if (PTR_ERR(new_tbl) != -EEXIST) data = ERR_CAST(new_tbl);
rht_unlock(tbl, bkt, flags);
- if (PTR_ERR(data) == -ENOENT && !new_tbl) { - atomic_inc(&ht->nelems); - if (rht_grow_above_75(ht, tbl)) - schedule_work(&ht->run_work); - } + if (inserted && rht_grow_above_75(ht, tbl)) + schedule_work(&ht->run_work); } } while (!IS_ERR_OR_NULL(new_tbl));