* [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
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