On Thu, 24 Mar 2022 at 09:44, Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote: > > On Thu, Mar 24, 2022 at 11:05 AM Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > On Wed, Mar 23, 2022 at 7:19 PM Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote: > > > > > > After this commit, the rules of dentry allocations changed. > > > The dentry should be allocated by kmem_cache_alloc_lru() > > > > Yeah, I looked at that, but I can't find any way there could be other > > allocations - not only are there strict rules how to initialize > > everything, but the dentries are free'd using > > > > kmem_cache_free(dentry_cache, dentry); > > > > and as a result if they were allocated any other way I would expect > > things would go south very quickly. > > > > The only other thing I could come up with is some breakage in the > > superblock lifetime so that &dentry->d_sb->s_dentry_lru would have > > problems, but again, this is *such* core code and not some unusual > > path, that I would be very very surprised if it wouldn't have > > triggered other issues long long ago. > > > > That's why I'd be more inclined to worry about the list_lru code being > > somehow broken. > > > > I also have the same concern. I have been trying for a few hours to > reproduce this issue, but it didn't oops on my test machine. And I'll > continue reproducing this. syzbot triggered it 222 times in a day, so it's most likely real: https://syzkaller.appspot.com/bug?extid=f8c45ccc7d5d45fc5965 There are 2 reproducers, but they look completely different. May be a race. You may also try to use syzbot's patch testing feature to get some additional debug info.
