This is a note to let you know that I've just added the patch titled ext4: limit entries returned when counting fsmap records to the 5.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ext4-limit-entries-returned-when-counting-fsmap-reco.patch and it can be found in the queue-5.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 2ec2a6729fac8645a72060613f9826baa803f194 Author: Darrick J. Wong <darrick.wong@xxxxxxxxxx> Date: Thu Oct 1 15:21:48 2020 -0700 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@xxxxxxxxxx> Link: https://lore.kernel.org/r/20201001222148.GA49520@magnolia Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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++;