linux-kernel - [PATCH 4.19 140/264] xfs: limit entries returned when counting fsmap records

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Message-Id: <20201027135437.262433510@linuxfoundation.org>
Date:   Tue, 27 Oct 2020 14:53:18 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Christoph Hellwig <hch@....de>,
        Chandan Babu R <chandanrlinux@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 140/264] xfs: limit entries returned when counting fsmap records

From: Darrick J. Wong <darrick.wong@...cle.com>

[ Upstream commit acd1ac3aa22fd58803a12d26b1ab7f70232f8d8d ]

If userspace asked fsmap to count the number of entries, we cannot
return more than UINT_MAX entries because fmh_entries is u32.
Therefore, stop counting if we hit this limit or else we will waste time
to return truncated results.

Fixes: e89c041338ed ("xfs: implement the GETFSMAP ioctl")
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Chandan Babu R <chandanrlinux@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/xfs/xfs_fsmap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
index 3d76a9e35870a..75b57b683d3e6 100644
--- a/fs/xfs/xfs_fsmap.c
+++ b/fs/xfs/xfs_fsmap.c
@@ -259,6 +259,9 @@ xfs_getfsmap_helper(
 
 	/* Are we just counting mappings? */
 	if (info->head->fmh_count == 0) {
+		if (info->head->fmh_entries == UINT_MAX)
+			return -ECANCELED;
+
 		if (rec_daddr > info->next_daddr)
 			info->head->fmh_entries++;
 
-- 
2.25.1