From: Herbert Xu herbert@gondor.apana.org.au
[ 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@purdue.edu Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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,