CVE-2023-53149

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ext4: avoid deadlock in fs reclaim with page writeback<br /> <br /> Ext4 has a filesystem wide lock protecting ext4_writepages() calls to<br /> avoid races with switching of journalled data flag or inode format. This<br /> lock can however cause a deadlock like:<br /> <br /> CPU0 CPU1<br /> <br /> ext4_writepages()<br /> percpu_down_read(sbi-&gt;s_writepages_rwsem);<br /> ext4_change_inode_journal_flag()<br /> percpu_down_write(sbi-&gt;s_writepages_rwsem);<br /> - blocks, all readers block from now on<br /> ext4_do_writepages()<br /> ext4_init_io_end()<br /> kmem_cache_zalloc(io_end_cachep, GFP_KERNEL)<br /> fs_reclaim frees dentry...<br /> dentry_unlink_inode()<br /> iput() - last ref =&gt;<br /> iput_final() - inode dirty =&gt;<br /> write_inode_now()...<br /> ext4_writepages() tries to acquire sbi-&gt;s_writepages_rwsem<br /> and blocks forever<br /> <br /> Make sure we cannot recurse into filesystem reclaim from writeback code<br /> to avoid the deadlock.