ext4: validate the debug_want_extra_isize mount option at parse time
authorTheodore Ts'o <tytso@mit.edu>
Sun, 15 Dec 2019 06:09:03 +0000 (01:09 -0500)
committerTheodore Ts'o <tytso@mit.edu>
Sun, 15 Dec 2019 23:05:20 +0000 (18:05 -0500)
commit9803387c55f7d2ce69aa64340c5fdc6b3027dbc8
tree7074d366004eb513473463ea2e11b5d348ef284a
parenta70fd5ac2ea787cafe07b69dadd16b3648ad64ac
ext4: validate the debug_want_extra_isize mount option at parse time

Instead of setting s_want_extra_size and then making sure that it is a
valid value afterwards, validate the field before we set it.  This
avoids races and other problems when remounting the file system.

Link: https://lore.kernel.org/r/20191215063020.GA11512@mit.edu
Cc: stable@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reported-and-tested-by: syzbot+4a39a025912b265cacef@syzkaller.appspotmail.com
fs/ext4/super.c