[Linux-stm32] Patch "minmax: relax check to allow comparison between unsigned arguments and signed constants" has been added to the 5.10-stable tree

[gregkh at linuxfoundation.org]

This is a note to let you know that I've just added the patch titled

    minmax: relax check to allow comparison between unsigned arguments and signed constants

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     minmax-relax-check-to-allow-comparison-between-unsigned-arguments-and-signed-constants.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.


>From prvs=378230090=farbere at amazon.com Fri Oct 17 11:09:53 2025
From: Eliav Farber <farbere at amazon.com>
Date: Fri, 17 Oct 2025 09:05:04 +0000
Subject: minmax: relax check to allow comparison between unsigned arguments and signed constants
To: <gregkh at linuxfoundation.org>, <stable at vger.kernel.org>, <linux at armlinux.org.uk>, <jdike at addtoit.com>, <richard at nod.at>, <anton.ivanov at cambridgegreys.com>, <dave.hansen at linux.intel.com>, <luto at kernel.org>, <peterz at infradead.org>, <tglx at linutronix.de>, <mingo at redhat.com>, <bp at alien8.de>, <x86 at kernel.org>, <hpa at zytor.com>, <tony.luck at intel.com>, <qiuxu.zhuo at intel.com>, <mchehab at kernel.org>, <james.morse at arm.com>, <rric at kernel.org>, <harry.wentland at amd.com>, <sunpeng.li at amd.com>, <alexander.deucher at amd.com>, <christian.koenig at amd.com>, <airlied at linux.ie>, <daniel at ffwll.ch>, <evan.quan at amd.com>, <james.qian.wang at arm.com>, <liviu.dudau at arm.com>, <mihail.atanassov at arm.com>, <brian.starkey at arm.com>, <maarten.lankhorst at linux.intel.com>, <mripard at kernel.org>, <tzimmermann at suse.de>, <robdclark at gmail.com>, <sean at poorly.run>, <jdelvare at suse.com>, <linux at roeck-us.net>, <fery at cypress.com>, <dmitry.torokhov at gmail.com>, <agk at redhat.com>, <snitzer at redhat.com>, <dm-devel at redhat.com>, <rajur at chelsio
 .com>, <davem at davemloft.net>, <kuba at kernel.org>, <peppe.cavallaro at st.com>, <alexandre.torgue at st.com>, <joabreu at synopsys.com>, <mcoquelin.stm32 at gmail.com>, <malattia at linux.it>, <hdegoede at redhat.com>, <mgross at linux.intel.com>, <intel-linux-scu at intel.com>, <artur.paszkiewicz at intel.com>, <jejb at linux.ibm.com>, <martin.petersen at oracle.com>, <sakari.ailus at linux.intel.com>, <clm at fb.com>, <josef at toxicpanda.com>, <dsterba at suse.com>, <xiang at kernel.org>, <chao at kernel.org>, <jack at suse.com>, <tytso at mit.edu>, <adilger.kernel at dilger.ca>, <dushistov at mail.ru>, <luc.vanoostenryck at gmail.com>, <rostedt at goodmis.org>, <pmladek at suse.com>, <sergey.senozhatsky at gmail.com>, <andriy.shevchenko at linux.intel.com>, <linux at rasmusvillemoes.dk>, <minchan at kernel.org>, <ngupta at vflare.org>, <akpm at linux-foundation.org>, <kuznet at ms2.inr.ac.ru>, <yoshfuji at linux-ipv6.org>, <pablo at netfilter.org>, <kadlec at netfilter.org>, <fw at strlen.de>, <jmaloy at redhat.com>, <ying.xue at windriver.com>, <willy at infradead.org>, <farbere at amazon.com>,
  <sashal at kernel.org>, <ruanjinjie at huawei.com>, <David.Laight at ACULAB.COM>, <herve.codina at bootlin.com>, <Jason at zx2c4.com>, <keescook at chromium.org>, <kbusch at kernel.org>, <nathan at kernel.org>, <bvanassche at acm.org>, <ndesaulniers at google.com>, <linux-arm-kernel at lists.infradead.org>, <linux-kernel at vger.kernel.org>, <linux-um at lists.infradead.org>, <linux-edac at vger.kernel.org>, <amd-gfx at lists.freedesktop.org>, <dri-devel at lists.freedesktop.org>, <linux-arm-msm at vger.kernel.org>, <freedreno at lists.freedesktop.org>, <linux-hwmon at vger.kernel.org>, <linux-input at vger.kernel.org>, <linux-media at vger.kernel.org>, <netdev at vger.kernel.org>, <linux-stm32 at st-md-mailman.stormreply.com>, <platform-driver-x86 at vger.kernel.org>, <linux-scsi at vger.kernel.org>, <linux-staging at lists.linux.dev>, <linux-btrfs at vger.kernel.org>, <linux-erofs at lists.ozlabs.org>, <linux-ext4 at vger.kernel.org>, <linux-sparse at vger.kernel.org>, <linux-mm at kvack.org>, <netfilter-devel at vger.kernel.org>, <coreteam at netfilter.org>, <tipc-discussion@
 lists.sourceforge.net>
Cc: Christoph Hellwig <hch at infradead.org>, Linus Torvalds <torvalds at linux-foundation.org>
Message-ID: <20251017090519.46992-13-farbere at amazon.com>

From: David Laight <David.Laight at ACULAB.COM>

[ Upstream commit 867046cc7027703f60a46339ffde91a1970f2901 ]

Allow (for example) min(unsigned_var, 20).

The opposite min(signed_var, 20u) is still errored.

Since a comparison between signed and unsigned never makes the unsigned
value negative it is only necessary to adjust the __types_ok() test.

Link: https://lkml.kernel.org/r/633b64e2f39e46bb8234809c5595b8c7@AcuMS.aculab.com
Signed-off-by: David Laight <david.laight at aculab.com>
Cc: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
Cc: Christoph Hellwig <hch at infradead.org>
Cc: Jason A. Donenfeld <Jason at zx2c4.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Matthew Wilcox (Oracle) <willy at infradead.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Eliav Farber <farbere at amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 include/linux/minmax.h |   24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -10,13 +10,18 @@
 /*
  * min()/max()/clamp() macros must accomplish three things:
  *
- * - avoid multiple evaluations of the arguments (so side-effects like
+ * - Avoid multiple evaluations of the arguments (so side-effects like
  *   "x++" happen only once) when non-constant.
- * - perform signed v unsigned type-checking (to generate compile
- *   errors instead of nasty runtime surprises).
- * - retain result as a constant expressions when called with only
+ * - Retain result as a constant expressions when called with only
  *   constant expressions (to avoid tripping VLA warnings in stack
  *   allocation usage).
+ * - Perform signed v unsigned type-checking (to generate compile
+ *   errors instead of nasty runtime surprises).
+ * - Unsigned char/short are always promoted to signed int and can be
+ *   compared against signed or unsigned arguments.
+ * - Unsigned arguments can be compared against non-negative signed constants.
+ * - Comparison of a signed argument against an unsigned constant fails
+ *   even if the constant is below __INT_MAX__ and could be cast to int.
  */
 #define __typecheck(x, y) \
 	(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
@@ -26,9 +31,14 @@
 	__builtin_choose_expr(__is_constexpr(is_signed_type(typeof(x))),	\
 		is_signed_type(typeof(x)), 0)
 
-#define __types_ok(x, y) 			\
-	(__is_signed(x) == __is_signed(y) ||	\
-		__is_signed((x) + 0) == __is_signed((y) + 0))
+/* True for a non-negative signed int constant */
+#define __is_noneg_int(x)	\
+	(__builtin_choose_expr(__is_constexpr(x) && __is_signed(x), x, -1) >= 0)
+
+#define __types_ok(x, y) 					\
+	(__is_signed(x) == __is_signed(y) ||			\
+		__is_signed((x) + 0) == __is_signed((y) + 0) ||	\
+		__is_noneg_int(x) || __is_noneg_int(y))
 
 #define __cmp_op_min <
 #define __cmp_op_max >


Patches currently in stable-queue which might be from farbere at amazon.com are

queue-5.10/minmax-allow-comparisons-of-int-against-unsigned-char-short.patch
queue-5.10/minmax-add-a-few-more-min_t-max_t-users.patch
queue-5.10/minmax-improve-macro-expansion-and-type-checking.patch
queue-5.10/minmax-fix-indentation-of-__cmp_once-and-__clamp_once.patch
queue-5.10/minmax.h-simplify-the-variants-of-clamp.patch
queue-5.10/minmax-add-in_range-macro.patch
queue-5.10/minmax.h-move-all-the-clamp-definitions-after-the-min-max-ones.patch
queue-5.10/minmax-allow-min-max-clamp-if-the-arguments-have-the-same-signedness.patch
queue-5.10/minmax-don-t-use-max-in-situations-that-want-a-c-constant-expression.patch
queue-5.10/minmax.h-remove-some-defines-that-are-only-expanded-once.patch
queue-5.10/minmax.h-use-build_bug_on_msg-for-the-lo-hi-test-in-clamp.patch
queue-5.10/minmax-simplify-min-max-clamp-implementation.patch
queue-5.10/minmax-deduplicate-__unconst_integer_typeof.patch
queue-5.10/minmax-simplify-and-clarify-min_t-max_t-implementation.patch
queue-5.10/minmax.h-add-whitespace-around-operators-and-after-commas.patch
queue-5.10/minmax-sanity-check-constant-bounds-when-clamping.patch
queue-5.10/minmax-avoid-overly-complicated-constant-expressions-in-vm-code.patch
queue-5.10/minmax-make-generic-min-and-max-macros-available-everywhere.patch
queue-5.10/minmax-fix-up-min3-and-max3-too.patch
queue-5.10/minmax.h-reduce-the-define-expansion-of-min-max-and-clamp.patch
queue-5.10/minmax-fix-header-inclusions.patch
queue-5.10/minmax-introduce-min-max-_array.patch
queue-5.10/btrfs-remove-duplicated-in_range-macro.patch
queue-5.10/overflow-tracing-define-the-is_signed_type-macro-once.patch
queue-5.10/minmax-relax-check-to-allow-comparison-between-unsigned-arguments-and-signed-constants.patch
queue-5.10/minmax-clamp-more-efficiently-by-avoiding-extra-comparison.patch
queue-5.10/minmax.h-update-some-comments.patch