diff options
| author | Vito Caputo <vcaputo@pengaru.com> | 2019-07-14 17:48:01 -0700 |
|---|---|---|
| committer | Vito Caputo <vcaputo@pengaru.com> | 2019-07-14 17:48:01 -0700 |
| commit | 8f241509d127f114f46c95769c0ec66e51be222b (patch) | |
| tree | b4883ce17646b80d53aea648977813824941117f /src/charts.c | |
| parent | b6a393bc55476bb65a974e8bd81482287b7f72f3 (diff) | |
charts: clamp %n length to buffer size
It appears I overlooked that %n returns the length that would have
been printed regardless of the destination buffer size, not what
was actually written. The man page is misleading here:
n The number of characters written so far is stored into the
integer pointed to by the corresponding argument. That
argument shall be an int *, or variant whose size matches
the (optionally) supplied integer length modifier. No argu‐
ment is converted. (This specifier is not supported by the
bionic C library.) The behavior is undefined if the conver‐
sion specification includes any flags, a field width, or a
precision.
In testing, it isn't the count of what's actually written. It's
oblivious of truncated output scenarios where the output buffer has
been exhausted before reaching the %n. The man page should be
clarified here.
This commit does the simplest thing and simply clamps the length to
the destination buffer - 1 (for the \0). %n is being used to avoid
needing an strlen() in this somewhat hot path, but it might make
sense to instead use the snprintf return value similarly clamped
instead of %n since %n isn't doing what was expected.
Diffstat (limited to 'src/charts.c')
| -rw-r--r-- | src/charts.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/src/charts.c b/src/charts.c index 0c0fa70..628b87a 100644 --- a/src/charts.c +++ b/src/charts.c @@ -590,6 +590,7 @@ static void draw_heirarchy_row(vwm_charts_t *charts, vwm_chart_t *chart, vmon_pr } else { /* we're a process having threads, suppress the wchan and state, as they will be displayed for the thread of same pid */ snprintf(str, sizeof(str), " %5i %n", proc->pid, &str_len); } + str_len = MIN(sizeof(str) - 1, str_len); str_width = XTextWidth(charts->chart_font, str, str_len); /* the process' comm label indented according to depth, followed with their respective argv's */ @@ -829,6 +830,7 @@ static void draw_chart(vwm_charts_t *charts, vwm_chart_t *chart, vmon_proc_t *pr /* only draw the \/\/\ and HZ if necessary */ if (chart->redraw_needed || charts->prev_sampling_interval != charts->sampling_interval) { snprintf(str, sizeof(str), "\\/\\/\\ %2iHz %n", (int)(charts->sampling_interval == INFINITY ? 0 : 1 / charts->sampling_interval), &str_len); + str_len = MIN(sizeof(str) - 1, str_len); XRenderFillRectangle(xserver->display, PictOpSrc, chart->text_picture, &chart_trans_color, 0, 0, /* dst x, y */ chart->visible_width, CHART_ROW_HEIGHT); /* dst w, h */ |