Messages in this thread | | | From | Andreas Gruenbacher <> | Date | Tue, 18 May 2021 20:17:36 +0200 | Subject | Re: [syzbot] KASAN: use-after-free Read in gfs2_glock_shrink_scan |
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Hi,
On Tue, May 18, 2021 at 10:49 AM Hillf Danton <hdanton@sina.com> wrote: > When put, glock is removed from lru by calling gfs2_glock_remove_from_lru() > in __gfs2_glock_put(), and check GLF_LRU under lru_lock. > > On the shrink scan path, GLF_LRU is cleared under lru_lock but because of > cond_resched_lock(&lru_lock) in gfs2_dispose_glock_lru() progress on the put > side can be made without deleting glock from lru. > > Keep GLF_LRU across the race window opened by cond_resched_lock(&lru_lock) to > ensure correct behavior on both sides - clrear GLF_LRU after list_del under > lru_lock.
can you please resend with a Signed-off-by tag and a valid patch (--- line missing)?
Thanks, Andreas
> +++ x/fs/gfs2/glock.c > @@ -1772,6 +1772,7 @@ __acquires(&lru_lock) > while(!list_empty(list)) { > gl = list_first_entry(list, struct gfs2_glock, gl_lru); > list_del_init(&gl->gl_lru); > + clear_bit(GLF_LRU, &gl->gl_flags); > if (!spin_trylock(&gl->gl_lockref.lock)) { > add_back_to_lru: > list_add(&gl->gl_lru, &lru_list); > @@ -1817,7 +1818,6 @@ static long gfs2_scan_glock_lru(int nr) > if (!test_bit(GLF_LOCK, &gl->gl_flags)) { > list_move(&gl->gl_lru, &dispose); > atomic_dec(&lru_count); > - clear_bit(GLF_LRU, &gl->gl_flags); > freed++; > continue; > } >
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