On Mon 28-07-25 18:07:15, Jiufei Xue wrote: > An use-after-free issue occurred when __mark_inode_dirty() get the > bdi_writeback that was in the progress of switching. > > CPU: 1 PID: 562 Comm: systemd-random- Not tainted 6.6.56-gb4403bd46a8e #1 > ...... > pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : __mark_inode_dirty+0x124/0x418 > lr : __mark_inode_dirty+0x118/0x418 > sp : ffffffc08c9dbbc0 > ........ > Call trace: > __mark_inode_dirty+0x124/0x418 > generic_update_time+0x4c/0x60 > file_modified+0xcc/0xd0 > ext4_buffered_write_iter+0x58/0x124 > ext4_file_write_iter+0x54/0x704 > vfs_write+0x1c0/0x308 > ksys_write+0x74/0x10c > __arm64_sys_write+0x1c/0x28 > invoke_syscall+0x48/0x114 > el0_svc_common.constprop.0+0xc0/0xe0 > do_el0_svc+0x1c/0x28 > el0_svc+0x40/0xe4 > el0t_64_sync_handler+0x120/0x12c > el0t_64_sync+0x194/0x198 > > Root cause is: > > systemd-random-seed kworker > ---------------------------------------------------------------------- > ___mark_inode_dirty inode_switch_wbs_work_fn > > spin_lock(&inode->i_lock); > inode_attach_wb > locked_inode_to_wb_and_lock_list > get inode->i_wb > spin_unlock(&inode->i_lock); > spin_lock(&wb->list_lock) > spin_lock(&inode->i_lock) > inode_io_list_move_locked > spin_unlock(&wb->list_lock) > spin_unlock(&inode->i_lock) > spin_lock(&old_wb->list_lock) > inode_do_switch_wbs > spin_lock(&inode->i_lock) > inode->i_wb = new_wb > spin_unlock(&inode->i_lock) > spin_unlock(&old_wb->list_lock) > wb_put_many(old_wb, nr_switched) > cgwb_release > old wb released > wb_wakeup_delayed() accesses wb, > then trigger the use-after-free > issue > > Fix this race condition by holding inode spinlock until > wb_wakeup_delayed() finished. > > Signed-off-by: Jiufei Xue <jiufei.xue@xxxxxxxxxxx> Looks good! Thanks for the fix. Feel free to add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > --- > fs/fs-writeback.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index cc57367fb..a07b8cf73 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -2608,10 +2608,6 @@ void __mark_inode_dirty(struct inode *inode, int flags) > wakeup_bdi = inode_io_list_move_locked(inode, wb, > dirty_list); > > - spin_unlock(&wb->list_lock); > - spin_unlock(&inode->i_lock); > - trace_writeback_dirty_inode_enqueue(inode); > - > /* > * If this is the first dirty inode for this bdi, > * we have to wake-up the corresponding bdi thread > @@ -2621,6 +2617,11 @@ void __mark_inode_dirty(struct inode *inode, int flags) > if (wakeup_bdi && > (wb->bdi->capabilities & BDI_CAP_WRITEBACK)) > wb_wakeup_delayed(wb); > + > + spin_unlock(&wb->list_lock); > + spin_unlock(&inode->i_lock); > + trace_writeback_dirty_inode_enqueue(inode); > + > return; > } > } > -- > 2.43.0 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
