In the Linux kernel, the following vulnerability has been resolved: ext4: skip extra isize expansion during mount to prevent deadlock ext4

In the Linux kernel, the following vulnerability has been resolved:

ext4: skip extra isize expansion during mount to prevent deadlock

ext4_try_to_expand_extra_isize() is called from __ext4_mark_inode_dirty()
while holding an active jbd2 handle. During mount (!SB_ACTIVE), the
expand path may move xattrs to external blocks and release ea_inodes via
iput(). When !SB_ACTIVE, iput() calls write_inode_now() which acquires
s_writepages_rwsem, creating a circular lock dependency:

s_writepages_rwsem --> jbd2_handle --> xattr_sem --> s_writepages_rwsem

This can be triggered via:

ext4_process_orphan() -> ext4_truncate() -> ext4_mark_inode_dirty()
-> ext4_try_to_expand_extra_isize()

or:

ext4_evict_inode() -> ext4_mark_inode_dirty()
-> ext4_try_to_expand_extra_isize()

Skip expansion when !SB_ACTIVE. This is a minor loss of functionality
(extra isize won't grow for these inodes during mount), which e2fsck
can resolve later if needed.