From b59cfbf77dc8368c2c90b012c79553613f4d70c3 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 18 Jan 2008 03:31:36 -0800 Subject: [PATCH] [FIB]: Fix rcu_dereference() abuses in fib_trie.c node_parent() and tnode_get_child() currently use rcu_dereference(). These functions are called from both - readers only paths (where rcu_dereference() is needed), and - writer path (where rcu_dereference() is not needed) To make explicit where rcu_dereference() is really needed, I introduced new node_parent_rcu() and tnode_get_child_rcu() functions which use rcu_dereference(), while node_parent() and tnode_get_child() dont use it. Then I changed calling sites where rcu_dereference() was really needed to call the _rcu() variants. This should have no impact but for alpha architecture, and may help future sparse checks. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/fib_trie.c | 33 +++++++++++++++++++++------------ 1 file changed, 21 insertions(+), 12 deletions(-) diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index fbc80d15827b..a52334d30cf8 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -165,9 +165,13 @@ static struct kmem_cache *fn_alias_kmem __read_mostly; static inline struct tnode *node_parent(struct node *node) { - struct tnode *ret; + return (struct tnode *)(node->parent & ~NODE_TYPE_MASK); +} + +static inline struct tnode *node_parent_rcu(struct node *node) +{ + struct tnode *ret = node_parent(node); - ret = (struct tnode *)(node->parent & ~NODE_TYPE_MASK); return rcu_dereference(ret); } @@ -177,13 +181,18 @@ static inline void node_set_parent(struct node *node, struct tnode *ptr) (unsigned long)ptr | NODE_TYPE(node)); } -/* rcu_read_lock needs to be hold by caller from readside */ +static inline struct node *tnode_get_child(struct tnode *tn, unsigned int i) +{ + BUG_ON(i >= 1U << tn->bits); -static inline struct node *tnode_get_child(struct tnode *tn, int i) + return tn->child[i]; +} + +static inline struct node *tnode_get_child_rcu(struct tnode *tn, unsigned int i) { - BUG_ON(i >= 1 << tn->bits); + struct node *ret = tnode_get_child(tn, i); - return rcu_dereference(tn->child[i]); + return rcu_dereference(ret); } static inline int tnode_child_length(const struct tnode *tn) @@ -938,7 +947,7 @@ fib_find_node(struct trie *t, u32 key) if (tkey_sub_equals(tn->key, pos, tn->pos-pos, key)) { pos = tn->pos + tn->bits; - n = tnode_get_child(tn, tkey_extract_bits(key, tn->pos, tn->bits)); + n = tnode_get_child_rcu(tn, tkey_extract_bits(key, tn->pos, tn->bits)); } else break; } @@ -1688,7 +1697,7 @@ static struct leaf *nextleaf(struct trie *t, struct leaf *thisleaf) p = (struct tnode*) trie; /* Start */ } else - p = node_parent(c); + p = node_parent_rcu(c); while (p) { int pos, last; @@ -1725,7 +1734,7 @@ static struct leaf *nextleaf(struct trie *t, struct leaf *thisleaf) up: /* No more children go up one step */ c = (struct node *) p; - p = node_parent(c); + p = node_parent_rcu(c); } return NULL; /* Ready. Root of trie */ } @@ -1987,7 +1996,7 @@ static struct node *fib_trie_get_next(struct fib_trie_iter *iter) iter->tnode, iter->index, iter->depth); rescan: while (cindex < (1<bits)) { - struct node *n = tnode_get_child(tn, cindex); + struct node *n = tnode_get_child_rcu(tn, cindex); if (n) { if (IS_LEAF(n)) { @@ -2006,7 +2015,7 @@ rescan: } /* Current node exhausted, pop back up */ - p = node_parent((struct node *)tn); + p = node_parent_rcu((struct node *)tn); if (p) { cindex = tkey_extract_bits(tn->key, p->pos, p->bits)+1; tn = p; @@ -2315,7 +2324,7 @@ static int fib_trie_seq_show(struct seq_file *seq, void *v) if (v == SEQ_START_TOKEN) return 0; - if (!node_parent(n)) { + if (!node_parent_rcu(n)) { if (iter->trie == iter->trie_local) seq_puts(seq, ":\n"); else -- 2.20.1