| Message ID | f04e61e1c69991559f5589080462320bf772499d.1729037131.git.gustavoars@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net: Avoid thousands of -Wflex-array-member-not-at-end warnings | expand |
From: "Gustavo A. R. Silva" <gustavoars@kernel.org> Date: Tue, 15 Oct 2024 18:32:43 -0600 > -Wflex-array-member-not-at-end was introduced in GCC-14, and we are > getting ready to enable it, globally. > > Address the following warnings by changing the type of the middle struct > members in a couple of composite structs, which are currently causing > trouble, from `struct sockaddr` to `struct sockaddr_legacy`. Note that > the latter struct doesn't contain a flexible-array member. > > include/uapi/linux/if_arp.h:118:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/if_arp.h:119:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/if_arp.h:121:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/if_arp.h:126:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/if_arp.h:127:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > Also, update some related code, accordingly. > > No binary differences are present after these changes. > > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > --- > include/uapi/linux/if_arp.h | 18 +++++++++--------- > net/ipv4/arp.c | 2 +- > 2 files changed, 10 insertions(+), 10 deletions(-) > > diff --git a/include/uapi/linux/if_arp.h b/include/uapi/linux/if_arp.h > index 4783af9fe520..cb6813f7783a 100644 > --- a/include/uapi/linux/if_arp.h > +++ b/include/uapi/linux/if_arp.h > @@ -115,18 +115,18 @@ > > /* ARP ioctl request. */ > struct arpreq { > - struct sockaddr arp_pa; /* protocol address */ > - struct sockaddr arp_ha; /* hardware address */ > - int arp_flags; /* flags */ > - struct sockaddr arp_netmask; /* netmask (only for proxy arps) */ > - char arp_dev[IFNAMSIZ]; > + struct sockaddr_legacy arp_pa; /* protocol address */ > + struct sockaddr_legacy arp_ha; /* hardware address */ > + int arp_flags; /* flags */ > + struct sockaddr_legacy arp_netmask; /* netmask (only for proxy arps) */ > + char arp_dev[IFNAMSIZ]; > }; > > struct arpreq_old { > - struct sockaddr arp_pa; /* protocol address */ > - struct sockaddr arp_ha; /* hardware address */ > - int arp_flags; /* flags */ > - struct sockaddr arp_netmask; /* netmask (only for proxy arps) */ > + struct sockaddr_legacy arp_pa; /* protocol address */ > + struct sockaddr_legacy arp_ha; /* hardware address */ > + int arp_flags; /* flags */ > + struct sockaddr arp_netmask; /* netmask (only for proxy arps) */ I think we can use _legacy here too, 14 bytes are enough for ARP. But whichever is fine to me because arpreq_old is not used in kernel, so Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> > }; > > /* ARP Flag values. */ > diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c > index 11c1519b3699..3a97efe1587b 100644 > --- a/net/ipv4/arp.c > +++ b/net/ipv4/arp.c > @@ -1185,7 +1185,7 @@ static int arp_req_get(struct net *net, struct arpreq *r) > > read_lock_bh(&neigh->lock); > memcpy(r->arp_ha.sa_data, neigh->ha, > - min(dev->addr_len, sizeof(r->arp_ha.sa_data_min))); > + min(dev->addr_len, sizeof(r->arp_ha.sa_data))); > r->arp_flags = arp_state_to_flags(neigh); > read_unlock_bh(&neigh->lock); > > -- > 2.34.1
On Tue, Oct 15, 2024 at 06:32:43PM -0600, Gustavo A. R. Silva wrote: > -Wflex-array-member-not-at-end was introduced in GCC-14, and we are > getting ready to enable it, globally. > > Address the following warnings by changing the type of the middle struct > members in a couple of composite structs, which are currently causing > trouble, from `struct sockaddr` to `struct sockaddr_legacy`. Note that > the latter struct doesn't contain a flexible-array member. > > include/uapi/linux/if_arp.h:118:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/if_arp.h:119:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/if_arp.h:121:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/if_arp.h:126:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/if_arp.h:127:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > Also, update some related code, accordingly. > > No binary differences are present after these changes. These are clearly UAPI files. It would be good to state in the commit message why this is a safe change, at the source level. Could user space code expect the type struct sockaddr and we are going to get warnings when struct sockaddr_legacy is found? Have you tried compiling an old arp binary, one that uses the IOCTL? The netfilter code also references it: http://charette.no-ip.com:81/programming/doxygen/netfilter/structarpreq.html You also need to submit a patch to the man page: https://man7.org/linux/man-pages/man7/arp.7.html You might also want to build some Rust code: https://docs.diesel.rs/master/libc/struct.arpreq.html I've no idea what Rust does when a C structure has a type change. Andrew
On Wed, Oct 16, 2024 at 02:30:02PM +0200, Andrew Lunn wrote: > On Tue, Oct 15, 2024 at 06:32:43PM -0600, Gustavo A. R. Silva wrote: > > -Wflex-array-member-not-at-end was introduced in GCC-14, and we are > > getting ready to enable it, globally. > > > > Address the following warnings by changing the type of the middle struct > > members in a couple of composite structs, which are currently causing > > trouble, from `struct sockaddr` to `struct sockaddr_legacy`. Note that > > the latter struct doesn't contain a flexible-array member. > > > > include/uapi/linux/if_arp.h:118:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > include/uapi/linux/if_arp.h:119:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > include/uapi/linux/if_arp.h:121:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > include/uapi/linux/if_arp.h:126:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > include/uapi/linux/if_arp.h:127:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > > > Also, update some related code, accordingly. > > > > No binary differences are present after these changes. > > These are clearly UAPI files. It would be good to state in the commit > message why this is a safe change, at the source level. I think we can avoid complicating UAPI by doing something like this in include/uapi/linux/socket.h: #ifdef __KERNEL__ #define __kernel_sockaddr_legacy sockaddr_legacy #else #define __kernel_sockaddr_legacy sockaddr #endif And then the UAPI changes can use __kernel_sockaddr_legacy and userspace will resolve to sockaddr (unchanged), and the kernel internals will resolve to sockaddr_legacy (fixing the warnings). -Kees
>> These are clearly UAPI files. It would be good to state in the commit >> message why this is a safe change, at the source level. Yes, I'll update it! > > I think we can avoid complicating UAPI by doing something like this in > include/uapi/linux/socket.h: > > #ifdef __KERNEL__ > #define __kernel_sockaddr_legacy sockaddr_legacy > #else > #define __kernel_sockaddr_legacy sockaddr > #endif > > And then the UAPI changes can use __kernel_sockaddr_legacy and userspace > will resolve to sockaddr (unchanged), and the kernel internals will > resolve to sockaddr_legacy (fixing the warnings). Here are a couple of test patches (Don't mind the changelog text): https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?h=testing/wfamnae-next20241015-2&id=c3b631a5036cbf45b3308d563bf74a518490f3e6 https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?h=testing/wfamnae-next20241015-2&id=66db096a530b95ce0ac33f9fdec66401ec5f2204 __kernel_sockaddr_legacy seems a bit too long, but at the same time it makes it quite clear what's going on. Thanks -- Gustavo
diff --git a/include/uapi/linux/if_arp.h b/include/uapi/linux/if_arp.h index 4783af9fe520..cb6813f7783a 100644 --- a/include/uapi/linux/if_arp.h +++ b/include/uapi/linux/if_arp.h @@ -115,18 +115,18 @@ /* ARP ioctl request. */ struct arpreq { - struct sockaddr arp_pa; /* protocol address */ - struct sockaddr arp_ha; /* hardware address */ - int arp_flags; /* flags */ - struct sockaddr arp_netmask; /* netmask (only for proxy arps) */ - char arp_dev[IFNAMSIZ]; + struct sockaddr_legacy arp_pa; /* protocol address */ + struct sockaddr_legacy arp_ha; /* hardware address */ + int arp_flags; /* flags */ + struct sockaddr_legacy arp_netmask; /* netmask (only for proxy arps) */ + char arp_dev[IFNAMSIZ]; }; struct arpreq_old { - struct sockaddr arp_pa; /* protocol address */ - struct sockaddr arp_ha; /* hardware address */ - int arp_flags; /* flags */ - struct sockaddr arp_netmask; /* netmask (only for proxy arps) */ + struct sockaddr_legacy arp_pa; /* protocol address */ + struct sockaddr_legacy arp_ha; /* hardware address */ + int arp_flags; /* flags */ + struct sockaddr arp_netmask; /* netmask (only for proxy arps) */ }; /* ARP Flag values. */ diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index 11c1519b3699..3a97efe1587b 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -1185,7 +1185,7 @@ static int arp_req_get(struct net *net, struct arpreq *r) read_lock_bh(&neigh->lock); memcpy(r->arp_ha.sa_data, neigh->ha, - min(dev->addr_len, sizeof(r->arp_ha.sa_data_min))); + min(dev->addr_len, sizeof(r->arp_ha.sa_data))); r->arp_flags = arp_state_to_flags(neigh); read_unlock_bh(&neigh->lock);
-Wflex-array-member-not-at-end was introduced in GCC-14, and we are getting ready to enable it, globally. Address the following warnings by changing the type of the middle struct members in a couple of composite structs, which are currently causing trouble, from `struct sockaddr` to `struct sockaddr_legacy`. Note that the latter struct doesn't contain a flexible-array member. include/uapi/linux/if_arp.h:118:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/if_arp.h:119:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/if_arp.h:121:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/if_arp.h:126:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/if_arp.h:127:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] Also, update some related code, accordingly. No binary differences are present after these changes. Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- include/uapi/linux/if_arp.h | 18 +++++++++--------- net/ipv4/arp.c | 2 +- 2 files changed, 10 insertions(+), 10 deletions(-)