From: Jakub Kicinski <jakub.kicinski@netronome.com>
To: Y Song <ys114321@gmail.com>
Cc: wen.yang99@zte.com.cn, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Quentin Monnet <quentin.monnet@netronome.com>,
Jiong Wang <jiong.wang@netronome.com>,
guro@fb.com, Sandipan Das <sandipan@linux.vnet.ibm.com>,
John Fastabend <john.fastabend@gmail.com>,
netdev <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
zhong.weidong@zte.com.cn, wang.yi59@zte.com.cn,
julia.lawall@lip6.fr
Subject: Re: [PATCH 3/4] tools: bpftool: fix potential NULL pointer dereference in do_load
Date: Wed, 21 Nov 2018 09:30:44 -0800 [thread overview]
Message-ID: <20181121093044.3c34b66b@cakuba.netronome.com> (raw)
In-Reply-To: <CAH3MdRVEoJXh1FRJKPiUvvphRLV9=-a8UV4pFUa=kq4qaWYjww@mail.gmail.com>
On Wed, 21 Nov 2018 09:18:06 -0800, Y Song wrote:
> On Tue, Nov 20, 2018 at 11:42 PM Wen Yang <wen.yang99@zte.com.cn> wrote:
> >
> > This patch fixes a possible null pointer dereference in
> > do_load, detected by the semantic patch
> > deref_null.cocci, with the following warning:
> >
> > ./tools/bpf/bpftool/prog.c:1021:23-25: ERROR: map_replace is NULL but dereferenced.
> >
> > The following code has potential null pointer references:
> > 881 map_replace = reallocarray(map_replace, old_map_fds + 1,
> > 882 sizeof(*map_replace));
> > 883 if (!map_replace) {
> > 884 p_err("mem alloc failed");
> > 885 goto err_free_reuse_maps;
> > 886 }
> >
> > ...
> > 1019 err_free_reuse_maps:
> > 1020 for (i = 0; i < old_map_fds; i++)
> > 1021 close(map_replace[i].fd);
> > 1022 free(map_replace);
>
> I did not see any issues here.
> We have code looks like:
> 867 struct map_replace *map_replace = NULL;
> 868 struct bpf_program *prog = NULL, *pos;
> 869 unsigned int old_map_fds = 0;
> ...
> 948 map_replace = reallocarray(map_replace,
> old_map_fds + 1,
> 949 sizeof(*map_replace));
> 950 if (!map_replace) {
> 951 p_err("mem alloc failed");
> 952 goto err_free_reuse_maps;
> 953 }
> 954 map_replace[old_map_fds].idx = idx;
> 955 map_replace[old_map_fds].name = name;
> 956 map_replace[old_map_fds].fd = fd;
> 957 old_map_fds++;
> ...
>
> old_map_fds becomes non zero if and only if map_replace is not NULL.
Note that this is a realloc in a loop, and map_replace will become NULL
again if realloc fails. We should check the return value of realloc()
without loosing the pointer to the old value. No?
> > Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
> > Reviewed-by: Tan Hu <tan.hu@zte.com.cn>
> > CC: Julia Lawall <julia.lawall@lip6.fr>
> > ---
> > tools/bpf/bpftool/prog.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> > index 5302ee2..de42187 100644
> > --- a/tools/bpf/bpftool/prog.c
> > +++ b/tools/bpf/bpftool/prog.c
> > @@ -1017,8 +1017,9 @@ static int do_load(int argc, char **argv)
> > err_close_obj:
> > bpf_object__close(obj);
> > err_free_reuse_maps:
> > - for (i = 0; i < old_map_fds; i++)
> > - close(map_replace[i].fd);
> > + if (map_replace)
> > + for (i = 0; i < old_map_fds; i++)
> > + close(map_replace[i].fd);
> > free(map_replace);
> > return -1;
> > }
> > --
> > 2.9.5
> >
next prev parent reply other threads:[~2018-11-21 17:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-21 7:43 [PATCH 3/4] tools: bpftool: fix potential NULL pointer dereference in do_load Wen Yang
2018-11-21 16:58 ` Jakub Kicinski
2018-11-21 17:18 ` Y Song
2018-11-21 17:30 ` Jakub Kicinski [this message]
2018-11-21 17:45 ` Y Song
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