* [PATCH iproute2-next] bpf: fix snprintf truncation warning
@ 2019-09-04 15:50 Andrea Claudi
2019-09-04 16:28 ` Andrea Claudi
2019-09-04 22:15 ` David Ahern
0 siblings, 2 replies; 6+ messages in thread
From: Andrea Claudi @ 2019-09-04 15:50 UTC (permalink / raw)
To: netdev; +Cc: stephen, dsahern
gcc v9.2.1 produces the following warning compiling iproute2:
bpf.c: In function ‘bpf_get_work_dir’:
bpf.c:784:49: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
| ^
bpf.c:784:2: note: ‘snprintf’ output between 2 and 4097 bytes into a destination of size 4096
784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fix it extending bpf_wrk_dir size by 1 byte for the extra "/" char.
Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
---
lib/bpf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/bpf.c b/lib/bpf.c
index 7d2a322ffbaec..95de7894a93ce 100644
--- a/lib/bpf.c
+++ b/lib/bpf.c
@@ -742,7 +742,7 @@ static int bpf_gen_hierarchy(const char *base)
static const char *bpf_get_work_dir(enum bpf_prog_type type)
{
static char bpf_tmp[PATH_MAX] = BPF_DIR_MNT;
- static char bpf_wrk_dir[PATH_MAX];
+ static char bpf_wrk_dir[PATH_MAX + 1];
static const char *mnt;
static bool bpf_mnt_cached;
const char *mnt_env = getenv(BPF_ENV_MNT);
--
2.21.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH iproute2-next] bpf: fix snprintf truncation warning
2019-09-04 15:50 [PATCH iproute2-next] bpf: fix snprintf truncation warning Andrea Claudi
@ 2019-09-04 16:28 ` Andrea Claudi
2019-09-04 22:15 ` David Ahern
1 sibling, 0 replies; 6+ messages in thread
From: Andrea Claudi @ 2019-09-04 16:28 UTC (permalink / raw)
To: linux-netdev; +Cc: Stephen Hemminger, David Ahern
On Wed, Sep 4, 2019 at 5:50 PM Andrea Claudi <aclaudi@redhat.com> wrote:
>
> gcc v9.2.1 produces the following warning compiling iproute2:
>
> bpf.c: In function ‘bpf_get_work_dir’:
> bpf.c:784:49: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
> 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> | ^
> bpf.c:784:2: note: ‘snprintf’ output between 2 and 4097 bytes into a destination of size 4096
> 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Fix it extending bpf_wrk_dir size by 1 byte for the extra "/" char.
>
> Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
> ---
> lib/bpf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/bpf.c b/lib/bpf.c
> index 7d2a322ffbaec..95de7894a93ce 100644
> --- a/lib/bpf.c
> +++ b/lib/bpf.c
> @@ -742,7 +742,7 @@ static int bpf_gen_hierarchy(const char *base)
> static const char *bpf_get_work_dir(enum bpf_prog_type type)
> {
> static char bpf_tmp[PATH_MAX] = BPF_DIR_MNT;
> - static char bpf_wrk_dir[PATH_MAX];
> + static char bpf_wrk_dir[PATH_MAX + 1];
> static const char *mnt;
> static bool bpf_mnt_cached;
> const char *mnt_env = getenv(BPF_ENV_MNT);
> --
> 2.21.0
>
Sorry, I forgot to add:
Fixes: e42256699cac ("bpf: make tc's bpf loader generic and move into lib")
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH iproute2-next] bpf: fix snprintf truncation warning
2019-09-04 15:50 [PATCH iproute2-next] bpf: fix snprintf truncation warning Andrea Claudi
2019-09-04 16:28 ` Andrea Claudi
@ 2019-09-04 22:15 ` David Ahern
2019-09-05 11:44 ` Andrea Claudi
1 sibling, 1 reply; 6+ messages in thread
From: David Ahern @ 2019-09-04 22:15 UTC (permalink / raw)
To: Andrea Claudi, netdev; +Cc: stephen, dsahern
On 9/4/19 9:50 AM, Andrea Claudi wrote:
> gcc v9.2.1 produces the following warning compiling iproute2:
>
> bpf.c: In function ‘bpf_get_work_dir’:
> bpf.c:784:49: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
> 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> | ^
> bpf.c:784:2: note: ‘snprintf’ output between 2 and 4097 bytes into a destination of size 4096
> 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Fix it extending bpf_wrk_dir size by 1 byte for the extra "/" char.
>
> Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
> ---
> lib/bpf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/bpf.c b/lib/bpf.c
> index 7d2a322ffbaec..95de7894a93ce 100644
> --- a/lib/bpf.c
> +++ b/lib/bpf.c
> @@ -742,7 +742,7 @@ static int bpf_gen_hierarchy(const char *base)
> static const char *bpf_get_work_dir(enum bpf_prog_type type)
> {
> static char bpf_tmp[PATH_MAX] = BPF_DIR_MNT;
> - static char bpf_wrk_dir[PATH_MAX];
> + static char bpf_wrk_dir[PATH_MAX + 1];
> static const char *mnt;
> static bool bpf_mnt_cached;
> const char *mnt_env = getenv(BPF_ENV_MNT);
>
PATH_MAX is meant to be the max length for a filesystem path including
the null terminator, so I think it would be better to change the
snprintf to 'sizeof(bpf_wrk_dir) - 1'.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH iproute2-next] bpf: fix snprintf truncation warning
2019-09-04 22:15 ` David Ahern
@ 2019-09-05 11:44 ` Andrea Claudi
2019-09-05 15:51 ` Stephen Hemminger
0 siblings, 1 reply; 6+ messages in thread
From: Andrea Claudi @ 2019-09-05 11:44 UTC (permalink / raw)
To: David Ahern; +Cc: linux-netdev, Stephen Hemminger, David Ahern
On Thu, Sep 5, 2019 at 12:15 AM David Ahern <dsahern@gmail.com> wrote:
>
> On 9/4/19 9:50 AM, Andrea Claudi wrote:
> > gcc v9.2.1 produces the following warning compiling iproute2:
> >
> > bpf.c: In function ‘bpf_get_work_dir’:
> > bpf.c:784:49: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
> > 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> > | ^
> > bpf.c:784:2: note: ‘snprintf’ output between 2 and 4097 bytes into a destination of size 4096
> > 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Fix it extending bpf_wrk_dir size by 1 byte for the extra "/" char.
> >
> > Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
> > ---
> > lib/bpf.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/lib/bpf.c b/lib/bpf.c
> > index 7d2a322ffbaec..95de7894a93ce 100644
> > --- a/lib/bpf.c
> > +++ b/lib/bpf.c
> > @@ -742,7 +742,7 @@ static int bpf_gen_hierarchy(const char *base)
> > static const char *bpf_get_work_dir(enum bpf_prog_type type)
> > {
> > static char bpf_tmp[PATH_MAX] = BPF_DIR_MNT;
> > - static char bpf_wrk_dir[PATH_MAX];
> > + static char bpf_wrk_dir[PATH_MAX + 1];
> > static const char *mnt;
> > static bool bpf_mnt_cached;
> > const char *mnt_env = getenv(BPF_ENV_MNT);
> >
>
> PATH_MAX is meant to be the max length for a filesystem path including
> the null terminator, so I think it would be better to change the
> snprintf to 'sizeof(bpf_wrk_dir) - 1'.
With 'sizeof(bpf_wrk_dir) - 1' snprintf simply truncates at byte 4095
instead of byte 4096.
This means that bpf_wrk_dir can again be truncated before the final
"/", as it is by now.
Am I missing something?
Trying your suggestion I have this slightly different warning message:
bpf.c: In function ‘bpf_get_work_dir’:
bpf.c:784:52: warning: ‘/’ directive output may be truncated writing 1
byte into a region of size between 0 and 4095 [-Wformat-truncation=]
784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir) - 1, "%s/", mnt);
| ^
bpf.c:784:2: note: ‘snprintf’ output between 2 and 4097 bytes into a
destination of size 4095
784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir) - 1, "%s/", mnt);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH iproute2-next] bpf: fix snprintf truncation warning
2019-09-05 11:44 ` Andrea Claudi
@ 2019-09-05 15:51 ` Stephen Hemminger
2019-09-06 10:19 ` Andrea Claudi
0 siblings, 1 reply; 6+ messages in thread
From: Stephen Hemminger @ 2019-09-05 15:51 UTC (permalink / raw)
To: Andrea Claudi; +Cc: David Ahern, linux-netdev, David Ahern
On Thu, 5 Sep 2019 13:44:55 +0200
Andrea Claudi <aclaudi@redhat.com> wrote:
> On Thu, Sep 5, 2019 at 12:15 AM David Ahern <dsahern@gmail.com> wrote:
> >
> > On 9/4/19 9:50 AM, Andrea Claudi wrote:
> > > gcc v9.2.1 produces the following warning compiling iproute2:
> > >
> > > bpf.c: In function ‘bpf_get_work_dir’:
> > > bpf.c:784:49: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
> > > 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> > > | ^
> > > bpf.c:784:2: note: ‘snprintf’ output between 2 and 4097 bytes into a destination of size 4096
> > > 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> > > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >
> > > Fix it extending bpf_wrk_dir size by 1 byte for the extra "/" char.
> > >
> > > Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
> > > ---
> > > lib/bpf.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/lib/bpf.c b/lib/bpf.c
> > > index 7d2a322ffbaec..95de7894a93ce 100644
> > > --- a/lib/bpf.c
> > > +++ b/lib/bpf.c
> > > @@ -742,7 +742,7 @@ static int bpf_gen_hierarchy(const char *base)
> > > static const char *bpf_get_work_dir(enum bpf_prog_type type)
> > > {
> > > static char bpf_tmp[PATH_MAX] = BPF_DIR_MNT;
> > > - static char bpf_wrk_dir[PATH_MAX];
> > > + static char bpf_wrk_dir[PATH_MAX + 1];
> > > static const char *mnt;
> > > static bool bpf_mnt_cached;
> > > const char *mnt_env = getenv(BPF_ENV_MNT);
> > >
> >
> > PATH_MAX is meant to be the max length for a filesystem path including
> > the null terminator, so I think it would be better to change the
> > snprintf to 'sizeof(bpf_wrk_dir) - 1'.
>
> With 'sizeof(bpf_wrk_dir) - 1' snprintf simply truncates at byte 4095
> instead of byte 4096.
> This means that bpf_wrk_dir can again be truncated before the final
> "/", as it is by now.
> Am I missing something?
>
> Trying your suggestion I have this slightly different warning message:
>
> bpf.c: In function ‘bpf_get_work_dir’:
> bpf.c:784:52: warning: ‘/’ directive output may be truncated writing 1
> byte into a region of size between 0 and 4095 [-Wformat-truncation=]
> 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir) - 1, "%s/", mnt);
> | ^
> bpf.c:784:2: note: ‘snprintf’ output between 2 and 4097 bytes into a
> destination of size 4095
> 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir) - 1, "%s/", mnt);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Why not rework this to use asprintf and avoid having huge buffers on stack?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH iproute2-next] bpf: fix snprintf truncation warning
2019-09-05 15:51 ` Stephen Hemminger
@ 2019-09-06 10:19 ` Andrea Claudi
0 siblings, 0 replies; 6+ messages in thread
From: Andrea Claudi @ 2019-09-06 10:19 UTC (permalink / raw)
To: Stephen Hemminger; +Cc: David Ahern, linux-netdev, David Ahern
On Thu, Sep 5, 2019 at 5:51 PM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> On Thu, 5 Sep 2019 13:44:55 +0200
> Andrea Claudi <aclaudi@redhat.com> wrote:
>
> > On Thu, Sep 5, 2019 at 12:15 AM David Ahern <dsahern@gmail.com> wrote:
> > >
> > > On 9/4/19 9:50 AM, Andrea Claudi wrote:
> > > > gcc v9.2.1 produces the following warning compiling iproute2:
> > > >
> > > > bpf.c: In function ‘bpf_get_work_dir’:
> > > > bpf.c:784:49: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
> > > > 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> > > > | ^
> > > > bpf.c:784:2: note: ‘snprintf’ output between 2 and 4097 bytes into a destination of size 4096
> > > > 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir), "%s/", mnt);
> > > > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >
> > > > Fix it extending bpf_wrk_dir size by 1 byte for the extra "/" char.
> > > >
> > > > Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
> > > > ---
> > > > lib/bpf.c | 2 +-
> > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/lib/bpf.c b/lib/bpf.c
> > > > index 7d2a322ffbaec..95de7894a93ce 100644
> > > > --- a/lib/bpf.c
> > > > +++ b/lib/bpf.c
> > > > @@ -742,7 +742,7 @@ static int bpf_gen_hierarchy(const char *base)
> > > > static const char *bpf_get_work_dir(enum bpf_prog_type type)
> > > > {
> > > > static char bpf_tmp[PATH_MAX] = BPF_DIR_MNT;
> > > > - static char bpf_wrk_dir[PATH_MAX];
> > > > + static char bpf_wrk_dir[PATH_MAX + 1];
> > > > static const char *mnt;
> > > > static bool bpf_mnt_cached;
> > > > const char *mnt_env = getenv(BPF_ENV_MNT);
> > > >
> > >
> > > PATH_MAX is meant to be the max length for a filesystem path including
> > > the null terminator, so I think it would be better to change the
> > > snprintf to 'sizeof(bpf_wrk_dir) - 1'.
> >
> > With 'sizeof(bpf_wrk_dir) - 1' snprintf simply truncates at byte 4095
> > instead of byte 4096.
> > This means that bpf_wrk_dir can again be truncated before the final
> > "/", as it is by now.
> > Am I missing something?
> >
> > Trying your suggestion I have this slightly different warning message:
> >
> > bpf.c: In function ‘bpf_get_work_dir’:
> > bpf.c:784:52: warning: ‘/’ directive output may be truncated writing 1
> > byte into a region of size between 0 and 4095 [-Wformat-truncation=]
> > 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir) - 1, "%s/", mnt);
> > | ^
> > bpf.c:784:2: note: ‘snprintf’ output between 2 and 4097 bytes into a
> > destination of size 4095
> > 784 | snprintf(bpf_wrk_dir, sizeof(bpf_wrk_dir) - 1, "%s/", mnt);
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Why not rework this to use asprintf and avoid having huge buffers on stack?
Thanks for the suggestion. There are a lot of similar usages in
lib/bpf.c, I'll send a v2 to rework them all.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-09-06 10:17 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-09-04 15:50 [PATCH iproute2-next] bpf: fix snprintf truncation warning Andrea Claudi
2019-09-04 16:28 ` Andrea Claudi
2019-09-04 22:15 ` David Ahern
2019-09-05 11:44 ` Andrea Claudi
2019-09-05 15:51 ` Stephen Hemminger
2019-09-06 10:19 ` Andrea Claudi
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.