[Linux-stm32] Patch "minmax: fix up min3() and max3() too" 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: fix up min3() and max3() too

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-fix-up-min3-and-max3-too.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 11:12:01 2025
From: Eliav Farber <farbere at amazon.com>
Date: Fri, 17 Oct 2025 09:05:12 +0000
Subject: minmax: fix up min3() and max3() too
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: Linus Torvalds <torvalds at linux-foundation.org>, David Laight <David.Laight at aculab.com>, Arnd Bergmann <arnd at kernel.org>
Message-ID: <20251017090519.46992-21-farbere at amazon.com>

From: Linus Torvalds <torvalds at linux-foundation.org>

[ Upstream commit 21b136cc63d2a9ddd60d4699552b69c214b32964 ]

David Laight pointed out that we should deal with the min3() and max3()
mess too, which still does excessive expansion.

And our current macros are actually rather broken.

In particular, the macros did this:

  #define min3(x, y, z) min((typeof(x))min(x, y), z)
  #define max3(x, y, z) max((typeof(x))max(x, y), z)

and that not only is a nested expansion of possibly very complex
arguments with all that involves, the typing with that "typeof()" cast
is completely wrong.

For example, imagine what happens in max3() if 'x' happens to be a
'unsigned char', but 'y' and 'z' are 'unsigned long'.  The types are
compatible, and there's no warning - but the result is just random
garbage.

No, I don't think we've ever hit that issue in practice, but since we
now have sane infrastructure for doing this right, let's just use it.
It fixes any excessive expansion, and also avoids these kinds of broken
type issues.

Requested-by: David Laight <David.Laight at aculab.com>
Acked-by: Arnd Bergmann <arnd at kernel.org>
Signed-off-by: Linus Torvalds <torvalds 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 |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -152,13 +152,20 @@
 #define umax(x, y)	\
 	__careful_cmp(max, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull)
 
+#define __careful_op3(op, x, y, z, ux, uy, uz) ({			\
+	__auto_type ux = (x); __auto_type uy = (y);__auto_type uz = (z);\
+	BUILD_BUG_ON_MSG(!__types_ok3(x,y,z,ux,uy,uz),			\
+		#op"3("#x", "#y", "#z") signedness error");		\
+	__cmp(op, ux, __cmp(op, uy, uz)); })
+
 /**
  * min3 - return minimum of three values
  * @x: first value
  * @y: second value
  * @z: third value
  */
-#define min3(x, y, z) min((typeof(x))min(x, y), z)
+#define min3(x, y, z) \
+	__careful_op3(min, x, y, z, __UNIQUE_ID(x_), __UNIQUE_ID(y_), __UNIQUE_ID(z_))
 
 /**
  * max3 - return maximum of three values
@@ -166,7 +173,8 @@
  * @y: second value
  * @z: third value
  */
-#define max3(x, y, z) max((typeof(x))max(x, y), z)
+#define max3(x, y, z) \
+	__careful_op3(max, x, y, z, __UNIQUE_ID(x_), __UNIQUE_ID(y_), __UNIQUE_ID(z_))
 
 /**
  * min_not_zero - return the minimum that is _not_ zero, unless both are zero


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