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    Subject[PATCH 5.4 279/408] ext4: limit entries returned when counting fsmap records
    Date
    From: Darrick J. Wong <darrick.wong@oracle.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@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>
    ---
    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


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