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netfilter: xt_time: use unsigned int for monthday bit shift 

The monthday field can be up to 31, and shifting a signed integer 1
by 31 positions (1 << 31) is undefined behavior in C, as the result
overflows a 32-bit signed int. Use 1U to ensure well-defined behavior
for all valid monthday values.

Change the weekday shift to 1U as well for consistency.

Fixes: ee4411a1b1 ("[NETFILTER]: x_tables: add xt_time match")
Reported-by: Klaudia Kloc <klaudia@vidocsecurity.com>
Reported-by: Dawid Moczadło <dawid@vidocsecurity.com>
Tested-by: Jenny Guanni Qu <qguanni@gmail.com>
Signed-off-by: Jenny Guanni Qu <qguanni@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
This commit is contained in:
Jenny Guanni Qu 2026-03-12 14:59:49 +00:00 committed by Florian Westphal
parent f62a218a94
commit 00050ec08c
1 changed files with 2 additions and 2 deletions
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4
net/netfilter/xt_time.c
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@ -223,13 +223,13 @@ time_mt(const struct sk_buff *skb, struct xt_action_param *par)
localtime_2(&current_time, stamp);
if (!(info->weekdays_match & (1 << current_time.weekday)))
if (!(info->weekdays_match & (1U << current_time.weekday)))
return false;
/* Do not spend time computing monthday if all days match anyway */
if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) {
localtime_3(&current_time, stamp);
if (!(info->monthdays_match & (1 << current_time.monthday)))
if (!(info->monthdays_match & (1U << current_time.monthday)))
return false;
}