The patch titled
Subject: nilfs2: avoid undefined behavior in nilfs_cnt32_ge macro
has been added to the -mm mm-nonmm-unstable branch. Its filename is
nilfs2-avoid-undefined-behavior-in-nilfs_cnt32_ge-macro.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-avoid-undefined-behavior-in-nilfs_cnt32_ge-macro.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Subject: nilfs2: avoid undefined behavior in nilfs_cnt32_ge macro
Date: Wed, 3 Jul 2024 03:35:12 +0900
According to the C standard 3.4.3p3, the result of signed integer overflow
is undefined. The macro nilfs_cnt32_ge(), which compares two sequence
numbers, uses signed integer subtraction that can overflow, and therefore
the result of the calculation may differ from what is expected due to
undefined behavior in different environments.
Similar to an earlier change to the jiffies-related comparison macros in
commit 5a581b367b5d ("jiffies: Avoid undefined behavior from signed
overflow"), avoid this potential issue by changing the definition of the
macro to perform the subtraction as unsigned integers, then cast the
result to a signed integer for comparison.
Link: https://lkml.kernel.org/r/20130727225828.GA11864@xxxxxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20240702183512.6390-1-konishi.ryusuke@xxxxxxxxx
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Fixes: 9ff05123e3bf ("nilfs2: segment constructor")
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/segment.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/nilfs2/segment.c~nilfs2-avoid-undefined-behavior-in-nilfs_cnt32_ge-macro
+++ a/fs/nilfs2/segment.c
@@ -136,7 +136,7 @@ static void nilfs_dispose_list(struct th
#define nilfs_cnt32_ge(a, b) \
(typecheck(__u32, a) && typecheck(__u32, b) && \
- ((__s32)(a) - (__s32)(b) >= 0))
+ ((__s32)((a) - (b)) >= 0))
static int nilfs_prepare_segment_lock(struct super_block *sb,
struct nilfs_transaction_info *ti)
_
Patches currently in -mm which might be from konishi.ryusuke@xxxxxxxxx are
nilfs2-fix-kernel-bug-on-rename-operation-of-broken-directory.patch
nilfs2-avoid-undefined-behavior-in-nilfs_cnt32_ge-macro.patch
