| Message ID | 1c12601bea3e9c18da6adc106bfcf5b7569e5dfb.1729037131.git.gustavoars@kernel.org |
|---|---|
| State | New |
| 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 18:27:16 -0600 > We are currently working on enabling the -Wflex-array-member-not-at-end > compiler option. This option has helped us detect several objects of > the type `struct sockaddr` that appear in the middle of composite > structures like `struct rtentry`, `struct compat_rtentry`, and others: > > include/uapi/linux/wireless.h:751:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/wireless.h:776:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/wireless.h:833:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/wireless.h:857:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/wireless.h:864:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/route.h:33:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/route.h:34:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/uapi/linux/route.h:35:25: 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: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] > include/net/compat.h:34:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > include/net/compat.h:35:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > fs/nfsd/nfsd.h:74:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > fs/nfsd/nfsd.h:75:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > In order to fix the warnings above, we introduce `struct sockaddr_legacy`. > The intention is to use it to replace the type of several struct members > in the middle of composite structures, currently of type `struct sockaddr`. > > These middle struct members are currently causing thousands of warnings > because `struct sockaddr` contains a flexible-array member, introduced > by commit b5f0de6df6dce ("net: dev: Convert sa_data to flexible array in > struct sockaddr"). > > The new `struct sockaddr_legacy` doesn't include a flexible-array > member, making it suitable for use as the type of middle members > in composite structs that don't really require the flexible-array > member in `struct sockaddr`, thus avoiding -Wflex-array-member-not-at-end > warnings. > > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > --- > include/linux/socket.h | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/include/linux/socket.h b/include/linux/socket.h > index d18cc47e89bd..f370ae0e6c82 100644 > --- a/include/linux/socket.h > +++ b/include/linux/socket.h > @@ -40,6 +40,25 @@ struct sockaddr { > }; > }; > > +/* > + * This is the legacy form of `struct sockaddr`. The original `struct sockaddr` > + * was modified in commit b5f0de6df6dce ("net: dev: Convert sa_data to flexible > + * array in struct sockaddR") due to the fact that "One of the worst offenders s/sockaddR/sockaddr/ The same typo? exists in the cover letter. With it fixed, Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> > + * of "fake flexible arrays" is struct sockaddr". This means that the original > + * `char sa_data[14]` behaved as a flexible array at runtime, so a proper > + * flexible-array member was introduced. > + * > + * This caused several flexible-array-in-the-middle issues: > + * https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wflex-array-member-not-at-end > + * > + * `struct sockaddr_legacy` replaces `struct sockaddr` in all instances where > + * objects of this type do not appear at the end of composite structures. > + */ > +struct sockaddr_legacy { > + sa_family_t sa_family; /* address family, AF_xxx */ > + char sa_data[14]; /* 14 bytes of protocol address */ > +}; > + > struct linger { > int l_onoff; /* Linger active */ > int l_linger; /* How long to linger for */ > -- > 2.34.1
diff --git a/include/linux/socket.h b/include/linux/socket.h index d18cc47e89bd..f370ae0e6c82 100644 --- a/include/linux/socket.h +++ b/include/linux/socket.h @@ -40,6 +40,25 @@ struct sockaddr { }; }; +/* + * This is the legacy form of `struct sockaddr`. The original `struct sockaddr` + * was modified in commit b5f0de6df6dce ("net: dev: Convert sa_data to flexible + * array in struct sockaddR") due to the fact that "One of the worst offenders + * of "fake flexible arrays" is struct sockaddr". This means that the original + * `char sa_data[14]` behaved as a flexible array at runtime, so a proper + * flexible-array member was introduced. + * + * This caused several flexible-array-in-the-middle issues: + * https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wflex-array-member-not-at-end + * + * `struct sockaddr_legacy` replaces `struct sockaddr` in all instances where + * objects of this type do not appear at the end of composite structures. + */ +struct sockaddr_legacy { + sa_family_t sa_family; /* address family, AF_xxx */ + char sa_data[14]; /* 14 bytes of protocol address */ +}; + struct linger { int l_onoff; /* Linger active */ int l_linger; /* How long to linger for */
We are currently working on enabling the -Wflex-array-member-not-at-end compiler option. This option has helped us detect several objects of the type `struct sockaddr` that appear in the middle of composite structures like `struct rtentry`, `struct compat_rtentry`, and others: include/uapi/linux/wireless.h:751:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/wireless.h:776:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/wireless.h:833:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/wireless.h:857:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/wireless.h:864:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/route.h:33:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/route.h:34:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/uapi/linux/route.h:35:25: 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: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] include/net/compat.h:34:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] include/net/compat.h:35:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] fs/nfsd/nfsd.h:74:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] fs/nfsd/nfsd.h:75:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] In order to fix the warnings above, we introduce `struct sockaddr_legacy`. The intention is to use it to replace the type of several struct members in the middle of composite structures, currently of type `struct sockaddr`. These middle struct members are currently causing thousands of warnings because `struct sockaddr` contains a flexible-array member, introduced by commit b5f0de6df6dce ("net: dev: Convert sa_data to flexible array in struct sockaddr"). The new `struct sockaddr_legacy` doesn't include a flexible-array member, making it suitable for use as the type of middle members in composite structs that don't really require the flexible-array member in `struct sockaddr`, thus avoiding -Wflex-array-member-not-at-end warnings. Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- include/linux/socket.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)