In the Linux kernel, the following vulnerability has been resolved: ext4: don't set SB_RDONLY after filesystem errors When the filesystem is mounted with errors=remount-ro, we were setting SB_RDONLY flag to stop all filesystem modifications. We knew this misses proper locking (sb->s_umount) and does not go through proper filesystem remount procedure but it has been the way this worked since early ext2 days and it was good enough for catastrophic situation damage mitigation. Recently, syzbot has found a way (see link) to trigger warnings in filesystem freezing because the code got confused by SB_RDONLY changing under its hands. Since these days we set EXT4_FLAGS_SHUTDOWN on the superblock which is enough to stop all filesystem modifications, modifying SB_RDONLY shouldn't be needed. So stop doing that.
https://git.kernel.org/stable/c/fbb177bc1d6487cd3e9b50ae0be2781b7297980d
https://git.kernel.org/stable/c/ee77c388469116565e009eaa704a60bc78489e09
https://git.kernel.org/stable/c/d3476f3dad4ad68ae5f6b008ea6591d1520da5d8
https://git.kernel.org/stable/c/58c0648e4c773f5b54f0cb63bc8c7c6bf52719a9
https://git.kernel.org/stable/c/4061e07f040a091f694f461b86a26cf95ae66439