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rhashtable: Fix rhashtable_try_insert test

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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: e1d3422c95 ("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>
This commit is contained in:
Herbert Xu 2025-01-14 11:15:19 +08:00
parent 076d9119cc
commit 9d4f8e54ce
1 changed files with 7 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

12
lib/rhashtable.c
View file

@ -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));