to #28557685

commit c36a71b4e35ab35340facdd6964a00956b9fef0a upstream.

If eh->eh_max is 0, EXT_MAX_EXTENT/INDEX would evaluate to unsigned
(-1) resulting in illegal memory accesses. Although there is no
consistent repro, we see that generic/019 sometimes crashes because of
this bug.

Ran gce-xfstests smoke and verified that there were no regressions.
Signed-off-by: NHarshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20200421023959.20879-2-harshadshirwadkar@gmail.comSigned-off-by: NTheodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NJeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>