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SubjectRe: [PATCH] kernel/rcutorture.c: use scnprintf() instead of sprintf()
On Mon, Oct 14, 2013 at 04:38:55PM +0800, Chen Gang wrote:
> If the contents is more than 4096 bytes (e.g. if have 1K cpus), current
> sprintf() will cause memory overflow.
>
> They are all test information which can be truncated, so use scnprintf()
> instead of sprintf(), also add 'max' parameter for related functions,
> also notice 80 columns boundary and parameters alignments.
>
> Test case:
>
> Fedora16 x86_64, 2 CPUs, 2GB RAM, [in/rm]mod with "torture_type=srcu".
>
> let maximize buffer to 256 to truncate in rcu_torture_printk().
> let maximize buffer to 410 to may truncate in srcu_torture_stats().
> let maximize buffer to 4096 (original size) to print full.
>
> it is a rcu test module, so not need additional test or consideration.
>
> Signed-off-by: Chen Gang <gang.chen@asianux.com>

At first glance, not a bad start.

Suppose that your goal was to make it avoid truncation. What would you
do differently?

Thanx, Paul

> ---
> kernel/rcutorture.c | 110 +++++++++++++++++++++++++++-----------------------
> 1 files changed, 59 insertions(+), 51 deletions(-)
>
> diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
> index be63101..107fd76 100644
> --- a/kernel/rcutorture.c
> +++ b/kernel/rcutorture.c
> @@ -370,7 +370,7 @@ struct rcu_torture_ops {
> void (*call)(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
> void (*cb_barrier)(void);
> void (*fqs)(void);
> - int (*stats)(char *page);
> + int (*stats)(char *page, int max);
> int irq_capable;
> int can_boost;
> const char *name;
> @@ -572,20 +572,20 @@ static void srcu_torture_barrier(void)
> srcu_barrier(&srcu_ctl);
> }
>
> -static int srcu_torture_stats(char *page)
> +static int srcu_torture_stats(char *page, int max)
> {
> int cnt = 0;
> int cpu;
> int idx = srcu_ctl.completed & 0x1;
>
> - cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
> - torture_type, TORTURE_FLAG, idx);
> + cnt += scnprintf(&page[cnt], max - cnt, "%s%s per-CPU(idx=%d):",
> + torture_type, TORTURE_FLAG, idx);
> for_each_possible_cpu(cpu) {
> - cnt += sprintf(&page[cnt], " %d(%lu,%lu)", cpu,
> - per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
> - per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
> + cnt += scnprintf(&page[cnt], max - cnt, " %d(%lu,%lu)", cpu,
> + per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
> + per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
> }
> - cnt += sprintf(&page[cnt], "\n");
> + cnt += scnprintf(&page[cnt], max - cnt, "\n");
> return cnt;
> }
>
> @@ -1047,7 +1047,7 @@ rcu_torture_reader(void *arg)
> * Create an RCU-torture statistics message in the specified buffer.
> */
> static int
> -rcu_torture_printk(char *page)
> +rcu_torture_printk(char *page, int max)
> {
> int cnt = 0;
> int cpu;
> @@ -1065,61 +1065,69 @@ rcu_torture_printk(char *page)
> if (pipesummary[i] != 0)
> break;
> }
> - cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
> - cnt += sprintf(&page[cnt],
> - "rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
> - rcu_torture_current,
> - rcu_torture_current_version,
> - list_empty(&rcu_torture_freelist),
> - atomic_read(&n_rcu_torture_alloc),
> - atomic_read(&n_rcu_torture_alloc_fail),
> - atomic_read(&n_rcu_torture_free));
> - cnt += sprintf(&page[cnt], "rtmbe: %d rtbke: %ld rtbre: %ld ",
> - atomic_read(&n_rcu_torture_mberror),
> - n_rcu_torture_boost_ktrerror,
> - n_rcu_torture_boost_rterror);
> - cnt += sprintf(&page[cnt], "rtbf: %ld rtb: %ld nt: %ld ",
> - n_rcu_torture_boost_failure,
> - n_rcu_torture_boosts,
> - n_rcu_torture_timers);
> - cnt += sprintf(&page[cnt],
> - "onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
> - n_online_successes, n_online_attempts,
> - n_offline_successes, n_offline_attempts,
> - min_online, max_online,
> - min_offline, max_offline,
> - sum_online, sum_offline, HZ);
> - cnt += sprintf(&page[cnt], "barrier: %ld/%ld:%ld",
> - n_barrier_successes,
> - n_barrier_attempts,
> - n_rcu_torture_barrier_error);
> - cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
> + cnt += scnprintf(&page[cnt], max - cnt, "%s%s ",
> + torture_type, TORTURE_FLAG);
> + cnt += scnprintf(&page[cnt], max - cnt,
> + "rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
> + rcu_torture_current,
> + rcu_torture_current_version,
> + list_empty(&rcu_torture_freelist),
> + atomic_read(&n_rcu_torture_alloc),
> + atomic_read(&n_rcu_torture_alloc_fail),
> + atomic_read(&n_rcu_torture_free));
> + cnt += scnprintf(&page[cnt], max - cnt,
> + "rtmbe: %d rtbke: %ld rtbre: %ld ",
> + atomic_read(&n_rcu_torture_mberror),
> + n_rcu_torture_boost_ktrerror,
> + n_rcu_torture_boost_rterror);
> + cnt += scnprintf(&page[cnt], max - cnt,
> + "rtbf: %ld rtb: %ld nt: %ld ",
> + n_rcu_torture_boost_failure,
> + n_rcu_torture_boosts,
> + n_rcu_torture_timers);
> + cnt += scnprintf(&page[cnt], max - cnt,
> + "onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
> + n_online_successes, n_online_attempts,
> + n_offline_successes, n_offline_attempts,
> + min_online, max_online,
> + min_offline, max_offline,
> + sum_online, sum_offline, HZ);
> + cnt += scnprintf(&page[cnt], max - cnt,
> + "barrier: %ld/%ld:%ld",
> + n_barrier_successes,
> + n_barrier_attempts,
> + n_rcu_torture_barrier_error);
> + cnt += scnprintf(&page[cnt], max - cnt, "\n%s%s ",
> + torture_type, TORTURE_FLAG);
> if (atomic_read(&n_rcu_torture_mberror) != 0 ||
> n_rcu_torture_barrier_error != 0 ||
> n_rcu_torture_boost_ktrerror != 0 ||
> n_rcu_torture_boost_rterror != 0 ||
> n_rcu_torture_boost_failure != 0 ||
> i > 1) {
> - cnt += sprintf(&page[cnt], "!!! ");
> + cnt += scnprintf(&page[cnt], max - cnt, "!!! ");
> atomic_inc(&n_rcu_torture_error);
> WARN_ON_ONCE(1);
> }
> - cnt += sprintf(&page[cnt], "Reader Pipe: ");
> + cnt += scnprintf(&page[cnt], max - cnt, "Reader Pipe: ");
> for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
> - cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
> - cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
> - cnt += sprintf(&page[cnt], "Reader Batch: ");
> + cnt += scnprintf(&page[cnt], max - cnt, " %ld", pipesummary[i]);
> + cnt += scnprintf(&page[cnt], max - cnt, "\n%s%s ",
> + torture_type, TORTURE_FLAG);
> + cnt += scnprintf(&page[cnt], max - cnt, "Reader Batch: ");
> for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
> - cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
> - cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
> - cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
> + cnt += scnprintf(&page[cnt], max - cnt, " %ld",
> + batchsummary[i]);
> + cnt += scnprintf(&page[cnt], max - cnt, "\n%s%s ",
> + torture_type, TORTURE_FLAG);
> + cnt += scnprintf(&page[cnt], max - cnt, "Free-Block Circulation: ");
> for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
> - cnt += sprintf(&page[cnt], " %d",
> - atomic_read(&rcu_torture_wcount[i]));
> + cnt += scnprintf(&page[cnt], max - cnt, " %d",
> + atomic_read(&rcu_torture_wcount[i]));
> }
> - cnt += sprintf(&page[cnt], "\n");
> + cnt += scnprintf(&page[cnt], max - cnt, "\n");
> if (cur_ops->stats)
> - cnt += cur_ops->stats(&page[cnt]);
> + cnt += cur_ops->stats(&page[cnt], max - cnt);
> return cnt;
> }
>
> @@ -1136,7 +1144,7 @@ rcu_torture_stats_print(void)
> {
> int cnt;
>
> - cnt = rcu_torture_printk(printk_buf);
> + cnt = rcu_torture_printk(printk_buf, sizeof(printk_buf));
> pr_alert("%s", printk_buf);
> }
>
> --
> 1.7.7.6
>



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