linux-kernel - [PATCH] xfs: fix diff_two_keys calculation for cnt btree

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Message-ID: <20250426134232.128864-1-pchelkin@ispras.ru>
Date: Sat, 26 Apr 2025 16:42:31 +0300
From: Fedor Pchelkin <pchelkin@...ras.ru>
To: Carlos Maiolino <cem@...nel.org>,
	"Darrick J. Wong" <djwong@...nel.org>
Cc: Fedor Pchelkin <pchelkin@...ras.ru>,
	Chandan Babu R <chandanbabu@...nel.org>,
	Brian Foster <bfoster@...hat.com>,
	linux-xfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org,
	Alexey Nepomnyashih <sdl@...ct.ru>,
	stable@...r.kernel.org
Subject: [PATCH] xfs: fix diff_two_keys calculation for cnt btree

Currently the difference is computed on 32-bit unsigned values although
eventually it is stored in a variable of int64_t type. This gives awkward
results, e.g. when the diff _should_ be negative, it is represented as
some large positive int64_t value.

Perform the calculations directly in int64_t as all other diff_two_keys
routines actually do.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: 08438b1e386b ("xfs: plumb in needed functions for range querying of the freespace btrees")
Cc: stable@...r.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
---
 fs/xfs/libxfs/xfs_alloc_btree.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
index a4ac37ba5d51..b3c54ae90e25 100644
--- a/fs/xfs/libxfs/xfs_alloc_btree.c
+++ b/fs/xfs/libxfs/xfs_alloc_btree.c
@@ -238,13 +238,13 @@ xfs_cntbt_diff_two_keys(
 	ASSERT(!mask || (mask->alloc.ar_blockcount &&
 			 mask->alloc.ar_startblock));
 
-	diff =  be32_to_cpu(k1->alloc.ar_blockcount) -
-		be32_to_cpu(k2->alloc.ar_blockcount);
+	diff = (int64_t)be32_to_cpu(k1->alloc.ar_blockcount) -
+			be32_to_cpu(k2->alloc.ar_blockcount);
 	if (diff)
 		return diff;
 
-	return  be32_to_cpu(k1->alloc.ar_startblock) -
-		be32_to_cpu(k2->alloc.ar_startblock);
+	return (int64_t)be32_to_cpu(k1->alloc.ar_startblock) -
+			be32_to_cpu(k2->alloc.ar_startblock);
 }
 
 static xfs_failaddr_t
-- 
2.49.0