From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
[ Upstream commit 1748f6a2cbc4694523f16da1c892b59861045b9d ]
The rcu_dereference call in rht_ptr_rcu is completely bogus because
we've already dereferenced the value in __rht_ptr and operated on it.
This causes potential double readings which could be fatal. The RCU
dereference must occur prior to the comparison in __rht_ptr.
This patch changes the order of RCU dereference so that it is done
first and the result is then fed to __rht_ptr. The RCU marking
changes have been minimised using casts which will be removed in
a follow-up patch.
Fixes: ba6306e3f648 ("rhashtable: Remove RCU marking from...")
Reported-by: "Gong, Sishuai" <sishuai@xxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/linux/rhashtable.h | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 70ebef866cc82..e3def7bbe9323 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -349,11 +349,11 @@ static inline void rht_unlock(struct bucket_table *tbl,
local_bh_enable();
}
-static inline struct rhash_head __rcu *__rht_ptr(
- struct rhash_lock_head *const *bkt)
+static inline struct rhash_head *__rht_ptr(
+ struct rhash_lock_head *p, struct rhash_lock_head __rcu *const *bkt)
{
- return (struct rhash_head __rcu *)
- ((unsigned long)*bkt & ~BIT(0) ?:
+ return (struct rhash_head *)
+ ((unsigned long)p & ~BIT(0) ?:
(unsigned long)RHT_NULLS_MARKER(bkt));
}
@@ -365,25 +365,26 @@ static inline struct rhash_head __rcu *__rht_ptr(
* access is guaranteed, such as when destroying the table.
*/
static inline struct rhash_head *rht_ptr_rcu(
- struct rhash_lock_head *const *bkt)
+ struct rhash_lock_head *const *p)
{
- struct rhash_head __rcu *p = __rht_ptr(bkt);
-
- return rcu_dereference(p);
+ struct rhash_lock_head __rcu *const *bkt = (void *)p;
+ return __rht_ptr(rcu_dereference(*bkt), bkt);
}
static inline struct rhash_head *rht_ptr(
- struct rhash_lock_head *const *bkt,
+ struct rhash_lock_head *const *p,
struct bucket_table *tbl,
unsigned int hash)
{
- return rht_dereference_bucket(__rht_ptr(bkt), tbl, hash);
+ struct rhash_lock_head __rcu *const *bkt = (void *)p;
+ return __rht_ptr(rht_dereference_bucket(*bkt, tbl, hash), bkt);
}
static inline struct rhash_head *rht_ptr_exclusive(
- struct rhash_lock_head *const *bkt)
+ struct rhash_lock_head *const *p)
{
- return rcu_dereference_protected(__rht_ptr(bkt), 1);
+ struct rhash_lock_head __rcu *const *bkt = (void *)p;
+ return __rht_ptr(rcu_dereference_protected(*bkt, 1), bkt);
}
static inline void rht_assign_locked(struct rhash_lock_head **bkt,
--
2.25.1
