Hello Antonin, On 12/27/19 10:15 PM, Antonin Décimo wrote: > PVS-Studio reports that in > > char buf[8192]; > /* ... */ > nh = (struct nlmsghdr *) buf, > > the pointer 'buf' is cast to a more strictly aligned pointer > type. This is undefined behaviour. One possible solution to make sure > that buf is correctly aligned is to declare buf as an array of struct > nlmsghdr. Other solutions include allocating the array on the heap, > use an union, or stdalign features. > With this patch, the buffer still contains 8192 bytes. > > This was raised on Stack Overflow: > https://stackoverflow.com/questions/57745580/netlink-receive-buffer-alignment Thanks. Patch applied. Cheers, Michael > --- > man7/netlink.7 | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/man7/netlink.7 b/man7/netlink.7 > index 81d4249..853dee6 100644 > --- a/man7/netlink.7 > +++ b/man7/netlink.7 > @@ -533,8 +533,9 @@ And the last example is about reading netlink message. > .in +4n > .EX > int len; > -char buf[8192]; /* 8192 to avoid message truncation on > - platforms with page size > 4096 */ > +/* 8192 to avoid message truncation on platforms with > + page size > 4096 */ > +struct nlmsghdr buf[8192/sizeof(struct nlmsghdr)]; > struct iovec iov = { buf, sizeof(buf) }; > struct sockaddr_nl sa; > struct msghdr msg; > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
