* [PATCH bpf] bpf: fix a buffer out-of-bound access when filling raw_tp link_info
@ 2020-08-21 19:10 Yonghong Song
2020-08-21 20:09 ` Andrii Nakryiko
0 siblings, 1 reply; 3+ messages in thread
From: Yonghong Song @ 2020-08-21 19:10 UTC (permalink / raw)
To: bpf, netdev
Cc: Alexei Starovoitov, Daniel Borkmann, kernel-team, Andrii Nakryiko
Commit f2e10bff16a0 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
added link query for raw_tp. One of fields in link_info is to
fill a user buffer with tp_name. The Scurrent checking only
declares "ulen && !ubuf" as invalid. So "!ulen && ubuf" will be
valid. Later on, we do "copy_to_user(ubuf, tp_name, ulen - 1)" which
may overwrite user memory incorrectly.
This patch fixed the problem by disallowing "!ulen && ubuf" case as well.
Fixes: f2e10bff16a0 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
Cc: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
kernel/bpf/syscall.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 86299a292214..ac6c784c0576 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2634,7 +2634,7 @@ static int bpf_raw_tp_link_fill_link_info(const struct bpf_link *link,
u32 ulen = info->raw_tracepoint.tp_name_len;
size_t tp_len = strlen(tp_name);
- if (ulen && !ubuf)
+ if (!ulen ^ !ubuf)
return -EINVAL;
info->raw_tracepoint.tp_name_len = tp_len + 1;
--
2.24.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH bpf] bpf: fix a buffer out-of-bound access when filling raw_tp link_info
2020-08-21 19:10 [PATCH bpf] bpf: fix a buffer out-of-bound access when filling raw_tp link_info Yonghong Song
@ 2020-08-21 20:09 ` Andrii Nakryiko
2020-08-25 4:08 ` Alexei Starovoitov
0 siblings, 1 reply; 3+ messages in thread
From: Andrii Nakryiko @ 2020-08-21 20:09 UTC (permalink / raw)
To: Yonghong Song
Cc: bpf, Networking, Alexei Starovoitov, Daniel Borkmann,
Kernel Team, Andrii Nakryiko
On Fri, Aug 21, 2020 at 12:11 PM Yonghong Song <yhs@fb.com> wrote:
>
> Commit f2e10bff16a0 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
> added link query for raw_tp. One of fields in link_info is to
> fill a user buffer with tp_name. The Scurrent checking only
> declares "ulen && !ubuf" as invalid. So "!ulen && ubuf" will be
> valid. Later on, we do "copy_to_user(ubuf, tp_name, ulen - 1)" which
> may overwrite user memory incorrectly.
>
> This patch fixed the problem by disallowing "!ulen && ubuf" case as well.
>
> Fixes: f2e10bff16a0 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
> Cc: Andrii Nakryiko <andriin@fb.com>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---
> kernel/bpf/syscall.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 86299a292214..ac6c784c0576 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2634,7 +2634,7 @@ static int bpf_raw_tp_link_fill_link_info(const struct bpf_link *link,
> u32 ulen = info->raw_tracepoint.tp_name_len;
> size_t tp_len = strlen(tp_name);
>
> - if (ulen && !ubuf)
> + if (!ulen ^ !ubuf)
> return -EINVAL;
I think my original idea was to allow ulen == 0 && ubuf != NULL as a
still valid way to get real ulen, but it's clearly wrong with ulen-1
below. So instead of special-casing ulen==0 for the case I wanted to
support, it's easier to disallow ulen==0 && ubuf!=NULL.
So thanks for the fix!
Acked-by: Andrii Nakryiko <andriin@fb.com>
>
> info->raw_tracepoint.tp_name_len = tp_len + 1;
> --
> 2.24.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH bpf] bpf: fix a buffer out-of-bound access when filling raw_tp link_info
2020-08-21 20:09 ` Andrii Nakryiko
@ 2020-08-25 4:08 ` Alexei Starovoitov
0 siblings, 0 replies; 3+ messages in thread
From: Alexei Starovoitov @ 2020-08-25 4:08 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Yonghong Song, bpf, Networking, Alexei Starovoitov,
Daniel Borkmann, Kernel Team, Andrii Nakryiko
On Fri, Aug 21, 2020 at 1:09 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Fri, Aug 21, 2020 at 12:11 PM Yonghong Song <yhs@fb.com> wrote:
> >
> > Commit f2e10bff16a0 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
> > added link query for raw_tp. One of fields in link_info is to
> > fill a user buffer with tp_name. The Scurrent checking only
> > declares "ulen && !ubuf" as invalid. So "!ulen && ubuf" will be
> > valid. Later on, we do "copy_to_user(ubuf, tp_name, ulen - 1)" which
> > may overwrite user memory incorrectly.
> >
> > This patch fixed the problem by disallowing "!ulen && ubuf" case as well.
> >
> > Fixes: f2e10bff16a0 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
> > Cc: Andrii Nakryiko <andriin@fb.com>
> > Signed-off-by: Yonghong Song <yhs@fb.com>
> > ---
> > kernel/bpf/syscall.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index 86299a292214..ac6c784c0576 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -2634,7 +2634,7 @@ static int bpf_raw_tp_link_fill_link_info(const struct bpf_link *link,
> > u32 ulen = info->raw_tracepoint.tp_name_len;
> > size_t tp_len = strlen(tp_name);
> >
> > - if (ulen && !ubuf)
> > + if (!ulen ^ !ubuf)
> > return -EINVAL;
>
> I think my original idea was to allow ulen == 0 && ubuf != NULL as a
> still valid way to get real ulen, but it's clearly wrong with ulen-1
> below. So instead of special-casing ulen==0 for the case I wanted to
> support, it's easier to disallow ulen==0 && ubuf!=NULL.
>
> So thanks for the fix!
>
> Acked-by: Andrii Nakryiko <andriin@fb.com>
Applied. Thanks
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-08-25 4:08 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-08-21 19:10 [PATCH bpf] bpf: fix a buffer out-of-bound access when filling raw_tp link_info Yonghong Song
2020-08-21 20:09 ` Andrii Nakryiko
2020-08-25 4:08 ` Alexei Starovoitov
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).