linux-kernel - [PATCH 5.9 553/757] ext4: limit entries returned when counting fsmap records

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Message-Id: <20201027135516.435502150@linuxfoundation.org>
Date:   Tue, 27 Oct 2020 14:53:23 +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>,
        Theodore Tso <tytso@....edu>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.9 553/757] ext4: limit entries returned when counting fsmap records

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

[ Upstream commit af8c53c8bc087459b1aadd4c94805d8272358d79 ]

If userspace asked fsmap to try 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: 0c9ec4beecac ("ext4: support GETFSMAP ioctls")
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Link: https://lore.kernel.org/r/20201001222148.GA49520@magnolia
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ext4/fsmap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ext4/fsmap.c b/fs/ext4/fsmap.c
index dbccf46f17709..37347ba868b70 100644
--- a/fs/ext4/fsmap.c
+++ b/fs/ext4/fsmap.c
@@ -108,6 +108,9 @@ static int ext4_getfsmap_helper(struct super_block *sb,
 
 	/* Are we just counting mappings? */
 	if (info->gfi_head->fmh_count == 0) {
+		if (info->gfi_head->fmh_entries == UINT_MAX)
+			return EXT4_QUERY_RANGE_ABORT;
+
 		if (rec_fsblk > info->gfi_next_fsblk)
 			info->gfi_head->fmh_entries++;
 
-- 
2.25.1