From: Darrick J. Wong <darrick.wong@oracle.com>
Date: Thu, 1 Oct 2020 22:21:48 +0000 (-0700)
Subject: ext4: limit entries returned when counting fsmap records
X-Git-Tag: v5.8.17~173
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6d0590647b756cc5b7e28f3c8577f0f9f253f0a2;p=thirdparty%2Fkernel%2Fstable.git

ext4: limit entries returned when counting fsmap records

[ 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@oracle.com>
Link: https://lore.kernel.org/r/20201001222148.GA49520@magnolia
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

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++;