[merged mm-nonmm-stable] lib-bch-fix-signed-left-shift-undefined-behavior.patch removed from -mm tree

[merged mm-nonmm-stable] lib-bch-fix-signed-left-shift-undefined-behavior.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: lib/bch: fix signed left-shift undefined behavior
has been removed from the -mm tree.  Its filename was
     lib-bch-fix-signed-left-shift-undefined-behavior.patch

This patch was dropped because it was merged into the mm-nonmm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Josh Law <objecting@objecting.org>
Subject: lib/bch: fix signed left-shift undefined behavior
Date: Wed, 18 Mar 2026 07:48:05 +0000

Patch series "lib/bch: fix undefined behavior from signed left-shifts".

Fix two instances of undefined behavior in lib/bch.c caused by
left-shifting signed integers into or past the sign bit.

While the kernel's -fno-strict-overflow flag prevents miscompilation
today, these are formally UB per C11 6.5.7p4 and trivial to fix.


This patch (of 2):

Use 1u instead of 1 to avoid undefined behavior when left-shifting into
the sign bit of a signed int.  deg() can return up to 31, and 1 << 31 is
UB per C11.

Link: https://lkml.kernel.org/r/20260318074806.16527-2-objecting@objecting.org
Signed-off-by: Josh Law <objecting@objecting.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ivan Djelic <ivan.djelic@parrot.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/bch.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/lib/bch.c~lib-bch-fix-signed-left-shift-undefined-behavior
+++ a/lib/bch.c
@@ -392,7 +392,7 @@ static void compute_syndromes(struct bch
 			for (j = 0; j < 2*t; j += 2)
 				syn[j] ^= a_pow(bch, (j+1)*(i+s));
 
-			poly ^= (1 << i);
+			poly ^= (1u << i);
 		}
 	} while (s > 0);
 
@@ -612,7 +612,7 @@ static int find_poly_deg2_roots(struct b
 		while (v) {
 			i = deg(v);
 			r ^= bch->xi_tab[i];
-			v ^= (1 << i);
+			v ^= (1u << i);
 		}
 		/* verify root */
 		if ((gf_sqr(bch, r)^r) == u) {
_

Patches currently in -mm which might be from objecting@objecting.org are

mm-damon-core-document-damos_commit_dests-failure-semantics.patch
lib-maple_tree-fix-swapped-arguments-in-mas_safe_pivot-call.patch
lib-idr-fix-ida_find_first_range-missing-ids-across-chunk-boundaries.patch