Messages in this thread | | | Date | Wed, 6 Jan 2016 15:13:02 -0800 | Subject | Re: [PATCH] scripts: recordmcount: fix incorrect use of sprintf | From | Kees Cook <> |
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On Wed, Jan 6, 2016 at 3:28 AM, Fengguang Wu <fengguang.wu@intel.com> wrote: > Hi Steven, > > On Mon, Jan 04, 2016 at 10:42:46AM -0500, Steven Rostedt wrote: >> On Wed, 30 Dec 2015 23:06:41 +0000 >> Colin King <colin.king@canonical.com> wrote: >> >> > From: Colin Ian King <colin.king@canonical.com> >> > >> > Fix build warning: >> > >> > scripts/recordmcount.c:589:4: warning: format not a string >> > literal and no format arguments [-Wformat-security] >> > sprintf("%s: failed\n", file); >> > >> > Fixes: a50bd43935586 ("ftrace/scripts: Have recordmcount copy the object file") >> > Signed-off-by: Colin Ian King <colin.king@canonical.com> >> > --- >> > scripts/recordmcount.c | 2 +- >> > 1 file changed, 1 insertion(+), 1 deletion(-) >> > >> > diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c >> > index 301d70b..e1675927 100644 >> > --- a/scripts/recordmcount.c >> > +++ b/scripts/recordmcount.c >> > @@ -586,7 +586,7 @@ main(int argc, char *argv[]) >> > do_file(file); >> > break; >> > case SJ_FAIL: /* error in do_file or below */ >> > - sprintf("%s: failed\n", file); >> > + fprintf(stderr, "%s: failed\n", file); >> >> Paper bag bug. I'm not sure how this passed my tests? My tests check >> for warnings. And I even got a "BUILD SUCCESS" from Fengguang Wu's >> kbuild test robot. > > Because the error will only show up on "gcc -Wformat-security".
I wish GCC were smarter about this. I would have hoped at least ONE of the various -Wformat... options would warn about "you did not actually specify a buffer for sprintf". But yeah, this comes from -Wformat-security (a subset of -Wformat-nonliteral), but can't be turned on by default, as mentioned by Fengguang.
> It tend to raise false positives, so Kees setup a dedicated tree > which enables -Wformat-security as well as quieting the common false > positives. In that way Kees can catch such problems from time to time, > however the limitation is, only upstreamed code can be tested in Kees' > tree.
-Kees
-- Kees Cook Chrome OS & Brillo Security
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