5.4-stable review patch. If anyone has any objections, please let me know.
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From: Ryusuke Konishi konishi.ryusuke@gmail.com
[ Upstream commit 0f3819e8c483771a59cf9d3190cd68a7a990083c ]
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@linux.vnet.ibm.com Link: https://lkml.kernel.org/r/20240702183512.6390-1-konishi.ryusuke@gmail.com Fixes: 9ff05123e3bf ("nilfs2: segment constructor") Signed-off-by: Ryusuke Konishi konishi.ryusuke@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nilfs2/segment.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c index 62c83193a5bb8..3c4272762779c 100644 --- a/fs/nilfs2/segment.c +++ b/fs/nilfs2/segment.c @@ -136,7 +136,7 @@ static void nilfs_dispose_list(struct the_nilfs *, struct list_head *, int);
#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)