From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cyril Hrubis Date: Wed, 19 Jul 2017 14:15:57 +0200 Subject: [LTP] [PATCH] lib/tst_timer_test.c: fix unsigned int overflow on RHEL5.11GA In-Reply-To: <1500274437-26154-1-git-send-email-yangx.jy@cn.fujitsu.com> References: <1500274437-26154-1-git-send-email-yangx.jy@cn.fujitsu.com> Message-ID: <20170719121557.GG1015@rei.lan> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it Hi! > On RHEL5.11GA, pselect01 gets signal SIGSEGV due to unsigned int > overflow when all members of the samples array are less than usec > in do_timer_test(). all tests which apply timer measurement library > could trigger this issue on RHEL5.11GA regularly. Ah righ, I've forgotten to add check for the array boundary there as well. > Signed-off-by: Xiao Yang > --- > lib/tst_timer_test.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/lib/tst_timer_test.c b/lib/tst_timer_test.c > index f30ad73..178e232 100644 > --- a/lib/tst_timer_test.c > +++ b/lib/tst_timer_test.c > @@ -295,9 +295,9 @@ void do_timer_test(long long usec, unsigned int nsamples) > i, samples[0], samples[i-1]); > } > > - for (i = nsamples - 1; samples[i] < usec; i--); > + for (i = nsamples - 1; i < nsamples && samples[i] < usec; i--); But this does not seem right, we are decrementing i, hence we should check that i > 0, otherwise we overflow anyway. With i < nsamples we will break the cycle after the overflow, which is wrong and works only by accident (since i is unsigned we overflow to UINT_MAX if we decrement 0). This should be the correct patch to fix the problem: diff --git a/lib/tst_timer_test.c b/lib/tst_timer_test.c index f30ad73dc..0b675f78d 100644 --- a/lib/tst_timer_test.c +++ b/lib/tst_timer_test.c @@ -295,7 +295,7 @@ void do_timer_test(long long usec, unsigned int nsamples) i, samples[0], samples[i-1]); } - for (i = nsamples - 1; samples[i] < usec; i--); + for (i = nsamples - 1; samples[i] < usec && i > 0; i--); if (i < nsamples - 1) { tst_res(TFAIL, "%s woken up early %u times range: [%lli,%lli]", -- Cyril Hrubis chrubis@suse.cz