* [PATCH] bpf, libbpf: Smatch: Fix potential NULL pointer dereference
@ 2019-07-02 10:25 Leo Yan
2019-07-02 15:34 ` Yonghong Song
2019-07-03 10:23 ` Daniel Borkmann
0 siblings, 2 replies; 4+ messages in thread
From: Leo Yan @ 2019-07-02 10:25 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Martin KaFai Lau, Song Liu,
Yonghong Song, netdev, bpf, linux-kernel, Dan Carpenter
Cc: Leo Yan
Based on the following report from Smatch, fix the potential
NULL pointer dereference check.
tools/lib/bpf/libbpf.c:3493
bpf_prog_load_xattr() warn: variable dereferenced before check 'attr'
(see line 3483)
3479 int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
3480 struct bpf_object **pobj, int *prog_fd)
3481 {
3482 struct bpf_object_open_attr open_attr = {
3483 .file = attr->file,
3484 .prog_type = attr->prog_type,
^^^^^^
3485 };
At the head of function, it directly access 'attr' without checking if
it's NULL pointer. This patch moves the values assignment after
validating 'attr' and 'attr->file'.
Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
tools/lib/bpf/libbpf.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 197b574406b3..809b633fa3d9 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3479,10 +3479,7 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
struct bpf_object **pobj, int *prog_fd)
{
- struct bpf_object_open_attr open_attr = {
- .file = attr->file,
- .prog_type = attr->prog_type,
- };
+ struct bpf_object_open_attr open_attr;
struct bpf_program *prog, *first_prog = NULL;
enum bpf_attach_type expected_attach_type;
enum bpf_prog_type prog_type;
@@ -3495,6 +3492,9 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
if (!attr->file)
return -EINVAL;
+ open_attr.file = attr->file;
+ open_attr.prog_type = attr->prog_type;
+
obj = bpf_object__open_xattr(&open_attr);
if (IS_ERR_OR_NULL(obj))
return -ENOENT;
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] bpf, libbpf: Smatch: Fix potential NULL pointer dereference
2019-07-02 10:25 [PATCH] bpf, libbpf: Smatch: Fix potential NULL pointer dereference Leo Yan
@ 2019-07-02 15:34 ` Yonghong Song
2019-07-03 10:23 ` Daniel Borkmann
1 sibling, 0 replies; 4+ messages in thread
From: Yonghong Song @ 2019-07-02 15:34 UTC (permalink / raw)
To: Leo Yan, Alexei Starovoitov, Daniel Borkmann, Martin Lau,
Song Liu, netdev, bpf, linux-kernel, Dan Carpenter
On 7/2/19 3:25 AM, Leo Yan wrote:
> Based on the following report from Smatch, fix the potential
> NULL pointer dereference check.
>
> tools/lib/bpf/libbpf.c:3493
> bpf_prog_load_xattr() warn: variable dereferenced before check 'attr'
> (see line 3483)
>
> 3479 int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
> 3480 struct bpf_object **pobj, int *prog_fd)
> 3481 {
> 3482 struct bpf_object_open_attr open_attr = {
> 3483 .file = attr->file,
> 3484 .prog_type = attr->prog_type,
> ^^^^^^
> 3485 };
>
> At the head of function, it directly access 'attr' without checking if
> it's NULL pointer. This patch moves the values assignment after
> validating 'attr' and 'attr->file'.
>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Yonghong Song <yhs@fb.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] bpf, libbpf: Smatch: Fix potential NULL pointer dereference
2019-07-02 10:25 [PATCH] bpf, libbpf: Smatch: Fix potential NULL pointer dereference Leo Yan
2019-07-02 15:34 ` Yonghong Song
@ 2019-07-03 10:23 ` Daniel Borkmann
2019-07-03 11:46 ` Leo Yan
1 sibling, 1 reply; 4+ messages in thread
From: Daniel Borkmann @ 2019-07-03 10:23 UTC (permalink / raw)
To: Leo Yan, Alexei Starovoitov, Martin KaFai Lau, Song Liu,
Yonghong Song, netdev, bpf, linux-kernel, Dan Carpenter
On 07/02/2019 12:25 PM, Leo Yan wrote:
> Based on the following report from Smatch, fix the potential
> NULL pointer dereference check.
>
> tools/lib/bpf/libbpf.c:3493
> bpf_prog_load_xattr() warn: variable dereferenced before check 'attr'
> (see line 3483)
>
> 3479 int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
> 3480 struct bpf_object **pobj, int *prog_fd)
> 3481 {
> 3482 struct bpf_object_open_attr open_attr = {
> 3483 .file = attr->file,
> 3484 .prog_type = attr->prog_type,
> ^^^^^^
> 3485 };
>
> At the head of function, it directly access 'attr' without checking if
> it's NULL pointer. This patch moves the values assignment after
> validating 'attr' and 'attr->file'.
>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
> tools/lib/bpf/libbpf.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 197b574406b3..809b633fa3d9 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -3479,10 +3479,7 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
> int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
> struct bpf_object **pobj, int *prog_fd)
> {
> - struct bpf_object_open_attr open_attr = {
> - .file = attr->file,
> - .prog_type = attr->prog_type,
> - };
Applied, thanks! Fyi, I retained the zeroing of open_attr as otherwise if we ever
extend struct bpf_object_open_attr in future, we'll easily miss this and pass in
garbage to bpf_object__open_xattr().
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] bpf, libbpf: Smatch: Fix potential NULL pointer dereference
2019-07-03 10:23 ` Daniel Borkmann
@ 2019-07-03 11:46 ` Leo Yan
0 siblings, 0 replies; 4+ messages in thread
From: Leo Yan @ 2019-07-03 11:46 UTC (permalink / raw)
To: Daniel Borkmann
Cc: Alexei Starovoitov, Martin KaFai Lau, Song Liu, Yonghong Song,
netdev, bpf, linux-kernel, Dan Carpenter
On Wed, Jul 03, 2019 at 12:23:05PM +0200, Daniel Borkmann wrote:
> On 07/02/2019 12:25 PM, Leo Yan wrote:
> > Based on the following report from Smatch, fix the potential
> > NULL pointer dereference check.
> >
> > tools/lib/bpf/libbpf.c:3493
> > bpf_prog_load_xattr() warn: variable dereferenced before check 'attr'
> > (see line 3483)
> >
> > 3479 int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
> > 3480 struct bpf_object **pobj, int *prog_fd)
> > 3481 {
> > 3482 struct bpf_object_open_attr open_attr = {
> > 3483 .file = attr->file,
> > 3484 .prog_type = attr->prog_type,
> > ^^^^^^
> > 3485 };
> >
> > At the head of function, it directly access 'attr' without checking if
> > it's NULL pointer. This patch moves the values assignment after
> > validating 'attr' and 'attr->file'.
> >
> > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> > ---
> > tools/lib/bpf/libbpf.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 197b574406b3..809b633fa3d9 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -3479,10 +3479,7 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
> > int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
> > struct bpf_object **pobj, int *prog_fd)
> > {
> > - struct bpf_object_open_attr open_attr = {
> > - .file = attr->file,
> > - .prog_type = attr->prog_type,
> > - };
>
> Applied, thanks! Fyi, I retained the zeroing of open_attr as otherwise if we ever
> extend struct bpf_object_open_attr in future, we'll easily miss this and pass in
> garbage to bpf_object__open_xattr().
Thanks for the info, Daniel.
I checked the link [1] and thanks for the improvement when applied this
patch.
Thanks,
Leo Yan
[1] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=33bae185f74d49a0d7b1bfaafb8e959efce0f243
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-07-02 15:34 ` Yonghong Song
2019-07-03 10:23 ` Daniel Borkmann
2019-07-03 11:46 ` Leo Yan
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