From 6daf14140129d30207ed6a0a69851fa6a3636bda Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 20 Feb 2020 07:59:14 -0600 Subject: netfilter: Replace zero-length array with flexible-array member The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] Lastly, fix checkpatch.pl warning WARNING: __aligned(size) is preferred over __attribute__((aligned(size))) in net/bridge/netfilter/ebtables.c This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Signed-off-by: Pablo Neira Ayuso --- net/netfilter/ipset/ip_set_bitmap_ip.c | 2 +- net/netfilter/ipset/ip_set_bitmap_ipmac.c | 2 +- net/netfilter/ipset/ip_set_bitmap_port.c | 2 +- net/netfilter/ipset/ip_set_hash_gen.h | 4 ++-- 4 files changed, 5 insertions(+), 5 deletions(-) (limited to 'net/netfilter/ipset') diff --git a/net/netfilter/ipset/ip_set_bitmap_ip.c b/net/netfilter/ipset/ip_set_bitmap_ip.c index 0a2196f59106..486959f70cf3 100644 --- a/net/netfilter/ipset/ip_set_bitmap_ip.c +++ b/net/netfilter/ipset/ip_set_bitmap_ip.c @@ -46,7 +46,7 @@ struct bitmap_ip { u8 netmask; /* subnet netmask */ struct timer_list gc; /* garbage collection */ struct ip_set *set; /* attached to this ip_set */ - unsigned char extensions[0] /* data extensions */ + unsigned char extensions[] /* data extensions */ __aligned(__alignof__(u64)); }; diff --git a/net/netfilter/ipset/ip_set_bitmap_ipmac.c b/net/netfilter/ipset/ip_set_bitmap_ipmac.c index 739e343efaf6..2310a316e0af 100644 --- a/net/netfilter/ipset/ip_set_bitmap_ipmac.c +++ b/net/netfilter/ipset/ip_set_bitmap_ipmac.c @@ -49,7 +49,7 @@ struct bitmap_ipmac { size_t memsize; /* members size */ struct timer_list gc; /* garbage collector */ struct ip_set *set; /* attached to this ip_set */ - unsigned char extensions[0] /* MAC + data extensions */ + unsigned char extensions[] /* MAC + data extensions */ __aligned(__alignof__(u64)); }; diff --git a/net/netfilter/ipset/ip_set_bitmap_port.c b/net/netfilter/ipset/ip_set_bitmap_port.c index b49978dd810d..e56ced66f202 100644 --- a/net/netfilter/ipset/ip_set_bitmap_port.c +++ b/net/netfilter/ipset/ip_set_bitmap_port.c @@ -37,7 +37,7 @@ struct bitmap_port { size_t memsize; /* members size */ struct timer_list gc; /* garbage collection */ struct ip_set *set; /* attached to this ip_set */ - unsigned char extensions[0] /* data extensions */ + unsigned char extensions[] /* data extensions */ __aligned(__alignof__(u64)); }; diff --git a/net/netfilter/ipset/ip_set_hash_gen.h b/net/netfilter/ipset/ip_set_hash_gen.h index e52d7b7597a0..1ee43752d6d3 100644 --- a/net/netfilter/ipset/ip_set_hash_gen.h +++ b/net/netfilter/ipset/ip_set_hash_gen.h @@ -76,7 +76,7 @@ struct hbucket { DECLARE_BITMAP(used, AHASH_MAX_TUNED); u8 size; /* size of the array */ u8 pos; /* position of the first free entry */ - unsigned char value[0] /* the array of the values */ + unsigned char value[] /* the array of the values */ __aligned(__alignof__(u64)); }; @@ -109,7 +109,7 @@ struct htable { u8 htable_bits; /* size of hash table == 2^htable_bits */ u32 maxelem; /* Maxelem per region */ struct ip_set_region *hregion; /* Region locks and ext sizes */ - struct hbucket __rcu *bucket[0]; /* hashtable buckets */ + struct hbucket __rcu *bucket[]; /* hashtable buckets */ }; #define hbucket(h, i) ((h)->bucket[i]) -- cgit v1.2.3