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netfilter: conntrack: avoid gcc-10 zero-length-bounds warning

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[ Upstream commit 2c407aca64 ]

gcc-10 warns around a suspicious access to an empty struct member:

net/netfilter/nf_conntrack_core.c: In function '__nf_conntrack_alloc':
net/netfilter/nf_conntrack_core.c:1522:9: warning: array subscript 0 is outside the bounds of an interior zero-length array 'u8[0]' {aka 'unsigned char[0]'} [-Wzero-length-bounds]
 1522 |  memset(&ct->__nfct_init_offset[0], 0,
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from net/netfilter/nf_conntrack_core.c:37:
include/net/netfilter/nf_conntrack.h:90:5: note: while referencing '__nfct_init_offset'
   90 |  u8 __nfct_init_offset[0];
      |     ^~~~~~~~~~~~~~~~~~

The code is correct but a bit unusual. Rework it slightly in a way that
does not trigger the warning, using an empty struct instead of an empty
array. There are probably more elegant ways to do this, but this is the
smallest change.

Fixes: c41884ce05 ("netfilter: conntrack: avoid zeroing timer")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Arnd Bergmann 2020-04-30 23:30:48 +02:00 committed by Greg Kroah-Hartman
parent 3bf3c3d83d
commit 7addf56d9a
2 changed files with 3 additions and 3 deletions
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2
include/net/netfilter/nf_conntrack.h
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@ -80,7 +80,7 @@ struct nf_conn {
struct hlist_node nat_bysource;
#endif
/* all members below initialized via memset */
u8 __nfct_init_offset[0];
struct { } __nfct_init_offset;
/* If we were expected by an expectation, this will be it */
struct nf_conn *master;

4
net/netfilter/nf_conntrack_core.c
View file

@ -1208,9 +1208,9 @@ __nf_conntrack_alloc(struct net *net,
*(unsigned long *)(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev) = hash;
ct->status = 0;
write_pnet(&ct->ct_net, net);
memset(&ct->__nfct_init_offset[0], 0,
memset(&ct->__nfct_init_offset, 0,
offsetof(struct nf_conn, proto) -
offsetof(struct nf_conn, __nfct_init_offset[0]));
offsetof(struct nf_conn, __nfct_init_offset));
nf_ct_zone_add(ct, zone);