From df5cfea3236ec479807353563abe00ddaa7c9dd8 Mon Sep 17 00:00:00 2001 From: Philip Withnall Date: Tue, 18 Feb 2025 17:28:33 +0000 Subject: gdatetime: Factor out an undersized variable For long input strings, it would have been possible for `i` to overflow. Avoid that problem by using the `tz_length` instead, so that we count up rather than down. This commit introduces no functional changes (outside of changing undefined behaviour), and can be verified using the identity `i === length - tz_length`. Signed-off-by: Philip Withnall --- glib/gdatetime.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/glib/gdatetime.c b/glib/gdatetime.c index 2710e56fd..5f6b9f752 100644 --- a/glib/gdatetime.c +++ b/glib/gdatetime.c @@ -1352,7 +1352,7 @@ static GTimeZone * parse_iso8601_timezone (const gchar *text, gsize length, size_t *tz_offset) { size_t tz_length; - gint i, offset_hours, offset_minutes; + gint offset_hours, offset_minutes; gint offset_sign = 1; GTimeZone *tz; const char *tz_start; @@ -1365,16 +1365,15 @@ parse_iso8601_timezone (const gchar *text, gsize length, size_t *tz_offset) } /* Look for '+' or '-' of offset */ - for (i = length - 1; i >= 0; i--) - if (text[i] == '+' || text[i] == '-') + for (tz_length = 1; tz_length <= length; tz_length++) + if (text[length - tz_length] == '+' || text[length - tz_length] == '-') { - offset_sign = text[i] == '-' ? -1 : 1; + offset_sign = text[length - tz_length] == '-' ? -1 : 1; break; } - if (i < 0) + if (tz_length > length) return NULL; - tz_start = text + i; - tz_length = length - i; + tz_start = text + length - tz_length; /* +hh:mm or -hh:mm */ if (tz_length == 6 && tz_start[3] == ':') -- 2.30.2