Messages in this thread | | | Subject | Re: KASAN: invalid-free in p9_client_create (2) | From | "wanghai (M)" <> | Date | Thu, 28 Jan 2021 19:39:12 +0800 |
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在 2021/1/28 3:31, Linus Torvalds 写道: > [ Participants list changed - syzbot thought this was networking and > p9, but it really looks entirely like a slub internal bug. I left the > innocent people on the list just to let them know they are innocent ] > > On Wed, Jan 27, 2021 at 6:27 AM syzbot > <syzbot+d0bd96b4696c1ef67991@syzkaller.appspotmail.com> wrote: >> The issue was bisected to: >> >> commit dde3c6b72a16c2db826f54b2d49bdea26c3534a2 >> Author: Wang Hai <wanghai38@huawei.com> >> Date: Wed Jun 3 22:56:21 2020 +0000 >> >> mm/slub: fix a memory leak in sysfs_slab_add() >> >> BUG: KASAN: double-free or invalid-free in slab_free mm/slub.c:3142 [inline] >> BUG: KASAN: double-free or invalid-free in kmem_cache_free+0x82/0x350 mm/slub.c:3158 > The p9 part of this bug report seems to be a red herring. > > The problem looks like it's simply the kmem_cache failure case, ie: > > - mm/slab_common.c: create_cache(): if the __kmem_cache_create() > fails, it does: > > out_free_cache: > kmem_cache_free(kmem_cache, s); > > - but __kmem_cache_create() - at least for slub() - will have done > > sysfs_slab_add(s) .. fails .. > -> kobject_del(&s->kobj); .. which frees s ... > > so the networking and p9 are fine, and the only reason p9 shows up in > the trace is that apparently it causes that failure in > kobject_init_and_add() for whatever reason, and that then exposes the > problem. > > So the added kobject_put() really looks buggy in this situation, and > the memory leak that that commit dde3c6b72a16 ("mm/slub: fix a memory > leak in sysfs_slab_add()") fixes is now a double free. > > And no, I don't think you can just remove the kmem_cache_free() in > create_cache(), because _other_ error cases of __kmem_cache_create() > do not free this. > > Wang Hai - comments? I'm inclined to revert that commit for now unless > somebody can come up with a proper fix.. > > Linus > . Hi, Linus. I'm sorry for introducing this bug, and I agree to revert it. I've just sent the revert patch. https://lore.kernel.org/patchwork/patch/1372475/
Thanks, Wang Hai
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