[PATCH v5] netlink: decode libudev netlink header
Dmitry V. Levin
ldv at altlinux.org
Tue Feb 27 16:13:08 UTC 2018
On Tue, Feb 27, 2018 at 05:57:03PM +0530, Harsha Sharma wrote:
> On Mon, Feb 26, 2018 at 7:40 AM, Dmitry V. Levin <ldv at altlinux.org> wrote:
> > On Wed, Jan 31, 2018 at 11:32:45PM +0530, Harsha Sharma wrote:
> >> * defs.h (decode_netlink_kobject_uevent): New prototype.
> >> * netlink.c (decode_netlink): Decode family kobject_uevent.
> >> * netlink_kobject_uevent.h: New file.
> >> * netlink_object_uevent.c: New file.
> >> * Makefile.am (strace_SOURCES): Add them.
> >>
> >> Signed-off-by: Harsha Sharma <harshasharmaiitr at gmail.com>
> >> ---
> >> Changes in v5:
> >> * print filter_* fields in hex
> >> * print messages after header in correct way
> >>
> >> Changes in v4:
> >> * Minor changes in decode_netlink_kobject_uevent
> >>
> >> Changes in v3:
> >> * Change changelog
> >> * minor changes in decode_netlink_kobject_uevent
> >> * omit irrelevant comments in netlink_kobject_uevent.h
> >>
> >> Changes in v2:
> >> * New file netlink_kobject_uevent.c
> >> * change location of netlink_kobject_uevent.h
> >> * add comments in netlink_kobject_uevent.h
> >> * add new files in Makefile.am
> >> * add func decode_netlink_kobject_uevent in defs.h
> >> * Use macros from print_fields.h instead of tprintf
> >> * minor changes in decode_netlink_kobject_uevent (including name)
> >>
> >> Makefile.am | 2 ++
> >> defs.h | 3 +++
> >> netlink.c | 2 +-
> >> netlink_kobject_uevent.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++
> >> netlink_kobject_uevent.h | 17 ++++++++++++
> >> 5 files changed, 90 insertions(+), 1 deletion(-)
> >> create mode 100644 netlink_kobject_uevent.c
> >> create mode 100644 netlink_kobject_uevent.h
> >>
> >> diff --git a/Makefile.am b/Makefile.am
> >> index 065ab819..20f97b06 100644
> >> --- a/Makefile.am
> >> +++ b/Makefile.am
> >> @@ -197,6 +197,8 @@ strace_SOURCES = \
> >> netlink.c \
> >> netlink.h \
> >> netlink_crypto.c \
> >> + netlink_kobject_uevent.c \
> >> + netlink_kobject_uevent.h \
> >> netlink_sock_diag.h \
> >> netlink_inet_diag.c \
> >> netlink_netlink_diag.c \
> >> diff --git a/defs.h b/defs.h
> >> index bbe0ecc9..d80ebc47 100644
> >> --- a/defs.h
> >> +++ b/defs.h
> >> @@ -685,6 +685,9 @@ DECL_NETLINK(route);
> >> DECL_NETLINK(selinux);
> >> DECL_NETLINK(sock_diag);
> >>
> >> +extern void
> >> +decode_netlink_kobject_uevent(struct tcb *, kernel_ulong_t addr,
> >> + kernel_ulong_t len);
> >> extern int tv_nz(const struct timeval *);
> >> extern int tv_cmp(const struct timeval *, const struct timeval *);
> >> extern double tv_float(const struct timeval *);
> >> diff --git a/netlink.c b/netlink.c
> >> index beb6ea4a..a714d29a 100644
> >> --- a/netlink.c
> >> +++ b/netlink.c
> >> @@ -629,7 +629,7 @@ decode_netlink(struct tcb *const tcp,
> >> const int family = get_fd_nl_family(tcp, fd);
> >>
> >> if (family == NETLINK_KOBJECT_UEVENT) {
> >> - printstrn(tcp, addr, len);
> >> + decode_netlink_kobject_uevent(tcp, addr, len);
> >> return;
> >> }
> >>
> >> diff --git a/netlink_kobject_uevent.c b/netlink_kobject_uevent.c
> >> new file mode 100644
> >> index 00000000..1ff7bd63
> >> --- /dev/null
> >> +++ b/netlink_kobject_uevent.c
> >> @@ -0,0 +1,67 @@
> >> +/*
> >> + * Copyright (c) 2018 Harsha Sharma <harshasharmaiitr at gmail.com>
> >> + * Copyright (c) 2017 The strace developers.
> >> + * All rights reserved.
> >> + *
> >> + * Redistribution and use in source and binary forms, with or without
> >> + * modification, are permitted provided that the following conditions
> >> + * are met:
> >> + * 1. Redistributions of source code must retain the above copyright
> >> + * notice, this list of conditions and the following disclaimer.
> >> + * 2. Redistributions in binary form must reproduce the above copyright
> >> + * notice, this list of conditions and the following disclaimer in the
> >> + * documentation and/or other materials provided with the distribution.
> >> + * 3. The name of the author may not be used to endorse or promote products
> >> + * derived from this software without specific prior written permission.
> >> + *
> >> + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
> >> + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
> >> + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
> >> + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
> >> + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
> >> + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
> >> + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
> >> + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> >> + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
> >> + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
> >> + */
> >> +
> >> +#include "defs.h"
> >> +#include "print_fields.h"
> >> +#include "netlink_kobject_uevent.h"
> >> +
> >> +#include <arpa/inet.h>
> >> +
> >> +void
> >> +decode_netlink_kobject_uevent(struct tcb *tcp, kernel_ulong_t addr,
> >> + kernel_ulong_t len)
> >> +{
> >> + struct udev_monitor_netlink_header uh;
> >> + const char *prefix = "libudev";
> >> +
> >> + if (len < sizeof(uh)) {
> >> + printstrn(tcp, addr, len);
> >> + } else if (!umove_or_printaddr(tcp, addr, &uh)) {
> >> + if (strcmp(uh.prefix, prefix) == 0) {
> >> + PRINT_FIELD_CSTRING("{{", uh, prefix);
> >> + tprintf(", magic=htonl(%#x)", ntohl(uh.magic));
> >> + PRINT_FIELD_U(", ", uh, header_size);
> >> + PRINT_FIELD_U(", ", uh, properties_off);
> >> + PRINT_FIELD_U(", ", uh, properties_len);
> >> + tprintf(", filter_subsystem_hash=htonl(%#x)", ntohl(uh.filter_subsystem_hash));
> >> + tprintf(", filter_devtype_hash=htonl(%#x)", ntohl(uh.filter_devtype_hash));
> >> + tprintf(", filter_tag_bloom_hi=htonl(%#x)", ntohl(uh.filter_tag_bloom_hi));
> >> + tprintf(", filter_tag_bloom_lo=htonl(%#x)", ntohl(uh.filter_tag_bloom_lo));
> >> + tprints("}");
> >> + const size_t offset = CMSG_ALIGN(sizeof(uh));
> >> + if (len > offset) {
> >> + tprints(", ");
> >> + printstrn(tcp, addr + offset , len - offset);
> >> + }
> >
> > Are you sure the use of CMSG_ALIGN is correct here?
> > It aligns on size_t boundary which is strange here given that
> > sizeof(size_t) is architecture-dependent while netlink packets should not be,
> > otherwise 32-bit clients won't be able to handle netlink packets sent by
> > a 64-bit kernel.
>
> Sorry my bad, Can I leave it as it was before i.e
> offset = sizeof(uh)
Yes, I think you can.
> Other than this, does this patch looks ok ?
Yes.
--
ldv
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