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@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:The issue was bisected to: commit dde3c6b72a16c2db826f54b2d49bdea26c3534a2 Author: Wang Hai <wanghai38@xxxxxxxxxx> 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:3158The 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
