From b521c89027f4b86af418083cb75db60a0e7a5997 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Mon, 26 Aug 2019 17:06:02 -0700 Subject: [PATCH] xfs: fix sign handling problem in xfs_bmbt_diff_two_keys In xfs_bmbt_diff_two_keys, we perform a signed int64_t subtraction with two unsigned 64-bit quantities. If the second quantity is actually the "maximum" key (all ones) as used in _query_all, the subtraction effectively becomes addition of two positive numbers and the function returns incorrect results. Fix this with explicit comparisons of the unsigned values. Nobody needs this now, but the online repair patches will need this to work properly. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner --- fs/xfs/libxfs/xfs_bmap_btree.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/fs/xfs/libxfs/xfs_bmap_btree.c b/fs/xfs/libxfs/xfs_bmap_btree.c index fbb18ba..ffe608d 100644 --- a/fs/xfs/libxfs/xfs_bmap_btree.c +++ b/fs/xfs/libxfs/xfs_bmap_btree.c @@ -400,8 +400,20 @@ xfs_bmbt_diff_two_keys( union xfs_btree_key *k1, union xfs_btree_key *k2) { - return (int64_t)be64_to_cpu(k1->bmbt.br_startoff) - - be64_to_cpu(k2->bmbt.br_startoff); + uint64_t a = be64_to_cpu(k1->bmbt.br_startoff); + uint64_t b = be64_to_cpu(k2->bmbt.br_startoff); + + /* + * Note: This routine previously casted a and b to int64 and subtracted + * them to generate a result. This lead to problems if b was the + * "maximum" key value (all ones) being signed incorrectly, hence this + * somewhat less efficient version. + */ + if (a > b) + return 1; + if (b > a) + return -1; + return 0; } static xfs_failaddr_t -- 2.7.4