Le 24/09/2023 à 18:00, Willem de Bruijn a écrit :
Christophe JAILLET wrote:
'n_tables' is small, UDP_TUNNEL_NIC_MAX_TABLES = 4 as a maximum. So there
is no real point to allocate the 'entries' pointers array with a dedicate
memory allocation.
Using a flexible array for struct udp_tunnel_nic->entries avoids the
overhead of an additional memory allocation.
This also saves an indirection when the array is accessed.
Finally, __counted_by() can be used for run-time bounds checking if
configured and supported by the compiler.
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
net/ipv4/udp_tunnel_nic.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)
diff --git a/net/ipv4/udp_tunnel_nic.c b/net/ipv4/udp_tunnel_nic.c
index 029219749785..b6d2d16189c0 100644
--- a/net/ipv4/udp_tunnel_nic.c
+++ b/net/ipv4/udp_tunnel_nic.c
@@ -47,7 +47,7 @@ struct udp_tunnel_nic {
unsigned int n_tables;
unsigned long missed;
- struct udp_tunnel_nic_table_entry **entries;
+ struct udp_tunnel_nic_table_entry *entries[] __counted_by(n_tables);
};
/* We ensure all work structs are done using driver state, but not the code.
@@ -725,16 +725,12 @@ udp_tunnel_nic_alloc(const struct udp_tunnel_nic_info *info,
struct udp_tunnel_nic *utn;
unsigned int i;
- utn = kzalloc(sizeof(*utn), GFP_KERNEL);
+ utn = kzalloc(struct_size(utn, entries, n_tables), GFP_KERNEL);
if (!utn)
return NULL;
utn->n_tables = n_tables;
Should utn->n_tables be initialized before first use of
struct_size(utn, entries, n_tables)?
It can't be.
struct_size() is used to compute the memory size to allocate.
Before the kzalloc() call, utn does not exist, so we can't write
anything to utn->n_tables. It is undefined at this point.
It is initialized the line just after, after the allocation, but before
any use.
CJ
