From: Uros Bizjak <ubizjak@gmail.com>
Date: Mon, 21 Jul 2025 17:45:57 +0000 (+0200)
Subject: ucount: fix atomic_long_inc_below() argument type
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f8cd9193b62e92ad25def5370ca8ea2bc7585381;p=thirdparty%2Flinux.git

ucount: fix atomic_long_inc_below() argument type

The type of u argument of atomic_long_inc_below() should be long to avoid
unwanted truncation to int.

The patch fixes the wrong argument type of an internal function to
prevent unwanted argument truncation.  It fixes an internal locking
primitive; it should not have any direct effect on userspace.

Mark said

: AFAICT there's no problem in practice because atomic_long_inc_below()
: is only used by inc_ucount(), and it looks like the value is
: constrained between 0 and INT_MAX.
:
: In inc_ucount() the limit value is taken from
: user_namespace::ucount_max[], and AFAICT that's only written by
: sysctls, to the table setup by setup_userns_sysctls(), where
: UCOUNT_ENTRY() limits the value between 0 and INT_MAX.
:
: This is certainly a cleanup, but there might be no functional issue in
: practice as above.

Link: https://lkml.kernel.org/r/20250721174610.28361-1-ubizjak@gmail.com
Fixes: f9c82a4ea89c ("Increase size of ucounts to atomic_long_t")
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Alexey Gladkov <legion@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: MengEn Sun <mengensun@tencent.com>
Cc: "Thomas Weißschuh" <linux@weissschuh.net>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 8686e329b8f2c..f629db485a079 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -199,7 +199,7 @@ void put_ucounts(struct ucounts *ucounts)
 	}
 }
 
-static inline bool atomic_long_inc_below(atomic_long_t *v, int u)
+static inline bool atomic_long_inc_below(atomic_long_t *v, long u)
 {
 	long c, old;
 	c = atomic_long_read(v);