[PATCH 6.19 140/220] netfilter: xt_time: use unsigned int for monthday bit shift

Greg Kroah-Hartman
2026-03-23T13:56:35Z

From: Jenny Guanni Qu <qguanni@gmail.com>

[ Upstream commit 00050ec08cecfda447e1209b388086d76addda3a ]

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: ee4411a1b1e0 ("[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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/xt_time.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/xt_time.c b/net/netfilter/xt_time.c
index 6aa12d0f54e23..61de85e02a40f 100644
--- a/net/netfilter/xt_time.c
+++ b/net/netfilter/xt_time.c
@@ -227,13 +227,13 @@ 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;
}

--
2.51.0