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authorGustavo A. R. Silva <gustavoars@kernel.org>2020-09-28 10:30:52 -0500
committerDavid S. Miller <davem@davemloft.net>2020-09-28 18:48:42 -0700
commitd61491a51f7e9e72df50d53f5d40825980bcb8b5 (patch)
treecb9df2db554d9ee3faf1d239e43be0630e4de044
parenta93b6a2b9f466afb4fa1d0bd23ae2f1d29914811 (diff)
net/sched: cls_u32: Replace one-element array with flexible-array member
There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. Refactor the code according to the use of a flexible-array member in struct tc_u_hnode and use the struct_size() helper to calculate the size for the allocations. Commit 5778d39d070b ("net_sched: fix struct tc_u_hnode layout in u32") makes it clear that the code is expected to dynamically allocate divisor + 1 entries for ->ht[] in tc_uhnode. Also, based on other observations, as the piece of code below: 1232 for (h = 0; h <= ht->divisor; h++) { 1233 for (n = rtnl_dereference(ht->ht[h]); 1234 n; 1235 n = rtnl_dereference(n->next)) { 1236 if (tc_skip_hw(n->flags)) 1237 continue; 1238 1239 err = u32_reoffload_knode(tp, n, add, cb, 1240 cb_priv, extack); 1241 if (err) 1242 return err; 1243 } 1244 } we can assume that, in general, the code is actually expecting to allocate that extra space for the one-element array in tc_uhnode, everytime it allocates memory for instances of tc_uhnode or tc_u_common structures. That's the reason for passing '1' as the last argument for struct_size() in the allocation for _root_ht_ and _tp_c_, and 'divisor + 1' in the allocation code for _ht_. [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays Tested-by: kernel test robot <lkp@intel.com> Link: https://lore.kernel.org/lkml/5f7062af.z3T9tn9yIPv6h5Ny%25lkp@intel.com/ Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/sched/cls_u32.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 7b69ab1993ba..54209a18d7fe 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -79,7 +79,7 @@ struct tc_u_hnode {
/* The 'ht' field MUST be the last field in structure to allow for
* more entries allocated at end of structure.
*/
- struct tc_u_knode __rcu *ht[1];
+ struct tc_u_knode __rcu *ht[];
};
struct tc_u_common {
@@ -353,7 +353,7 @@ static int u32_init(struct tcf_proto *tp)
void *key = tc_u_common_ptr(tp);
struct tc_u_common *tp_c = tc_u_common_find(key);
- root_ht = kzalloc(sizeof(*root_ht), GFP_KERNEL);
+ root_ht = kzalloc(struct_size(root_ht, ht, 1), GFP_KERNEL);
if (root_ht == NULL)
return -ENOBUFS;
@@ -364,7 +364,7 @@ static int u32_init(struct tcf_proto *tp)
idr_init(&root_ht->handle_idr);
if (tp_c == NULL) {
- tp_c = kzalloc(sizeof(*tp_c), GFP_KERNEL);
+ tp_c = kzalloc(struct_size(tp_c, hlist->ht, 1), GFP_KERNEL);
if (tp_c == NULL) {
kfree(root_ht);
return -ENOBUFS;
@@ -933,7 +933,7 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
NL_SET_ERR_MSG_MOD(extack, "Divisor can only be used on a hash table");
return -EINVAL;
}
- ht = kzalloc(sizeof(*ht) + divisor*sizeof(void *), GFP_KERNEL);
+ ht = kzalloc(struct_size(ht, ht, divisor + 1), GFP_KERNEL);
if (ht == NULL)
return -ENOBUFS;
if (handle == 0) {