Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
nilfs2: do not write dirty data after degenerating to read-only
According to syzbot’s report, mark_buffer_dirty() called from nilfs_segctor_do_construct() outputs a warning with some patterns after nilfs2 detects metadata corruption and degrades to read-only mode.
After such read-only degeneration, page cache data may be cleared through nilfs_clear_dirty_page() which may also clear the uptodate flag for their buffer heads. However, even after the degeneration, log writes are still performed by unmount processing etc., which causes mark_buffer_dirty() to be called for buffer heads without the “uptodate” flag and causes the warning.
Since any writes should not be done to a read-only file system in the first place, this fixes the warning in mark_buffer_dirty() by letting nilfs_segctor_do_construct() abort early if in read-only mode.
This also changes the retry check of nilfs_segctor_write_out() to avoid unnecessary log write retries if it detects -EROFS that nilfs_segctor_do_construct() returned.
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 6 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Oracle Linux 6 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
- Affected packages:
- kernel @ 4.18.0 (+15 more)
In the Linux kernel, the following vulnerability has been resolved:
nilfs2: do not write dirty data after degenerating to read-only
According to syzbot’s report, mark_buffer_dirty() called from nilfs_segctor_do_construct() outputs a warning with some patterns after nilfs2 detects metadata corruption and degrades to read-only mode.
After such read-only degeneration, page cache data may be cleared through nilfs_clear_dirty_page() which may also clear the uptodate flag for their buffer heads. However, even after the degeneration, log writes are still performed by unmount processing etc., which causes mark_buffer_dirty() to be called for buffer heads without the “uptodate” flag and causes the warning.
Since any writes should not be done to a read-only file system in the first place, this fixes the warning in mark_buffer_dirty() by letting nilfs_segctor_do_construct() abort early if in read-only mode.
This also changes the retry check of nilfs_segctor_write_out() to avoid unnecessary log write retries if it detects -EROFS that nilfs_segctor_do_construct() returned.