CVE-2024-50014

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

ext4: fix access to uninitialised lock in fc replay path

The following kernel trace can be triggered with fstest generic/629 when executed against a filesystem with fast-commit feature enabled:

INFO: trying to register non-static key. The code is fine but needs lockdep annotation, or maybe you didn't initialize this object before use? turning off the locking correctness validator. CPU: 0 PID: 866 Comm: mount Not tainted 6.10.0+ #11 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dumpstacklvl+0x66/0x90 registerlockclass+0x759/0x7d0 __lock_acquire+0x85/0x2630 ? __findgetblock+0xb4/0x380 lock_acquire+0xd1/0x2d0 ? __ext4journalgetwriteaccess+0xd5/0x160 rawspin_lock+0x33/0x40 ? __ext4journalgetwriteaccess+0xd5/0x160 __ext4journalgetwriteaccess+0xd5/0x160 ext4reserveinode_write+0x61/0xb0 _ext4markinodedirty+0x79/0x270 ? ext4extreplaysetiblocks+0x2f8/0x450 ext4extreplaysetiblocks+0x330/0x450 ext4fcreplay+0x14c8/0x1540 ? jread+0x88/0x2e0 ? rcuiswatching+0x11/0x40 doonepass+0x447/0xd00 jbd2journalrecover+0x139/0x1b0 jbd2journalload+0x96/0x390 ext4loadandinitjournal+0x253/0xd40 ext4fillsuper+0x2cc6/0x3180 ...

In the replay path there's an attempt to lock sbi->sbdevwblock in function ext4checkbdevwrite_error(). Unfortunately, at this point this spinlock has not been initialized yet. Moving it's initialization to an earlier point in __ext4fillsuper() fixes this splat.