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<812E97E8-668F-414D-9480-1D284834A034@linux.dev> X-Mimecast-Spam-Score: 1 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 7akeu6bam7dgp5wrnp6ipwoat5kksigc X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 9CC8440003 X-Rspam-User: X-HE-Tag: 1711015086-435143 X-HE-Meta: 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G8Jl7G7fsUWZCCIXlFuT8W4x6fHH/YCv3T194LNMEVF3ozHK/gnORiv+ZIhbJdUUMeu4aPxkniojBEnSWM/iZ+5X8D/PKqWsOpyONYE+QW2HSPTuhVOSYWPrtaV2Nl35 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 21.03.24 10:49, Muchun Song wrote: > > >> On Mar 21, 2024, at 12:04, syzbot wrote: >> >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: 78c3925c048c Merge tag 'soc-late-6.9' of git://git.kernel... >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=1267d879180000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=f3c2635ded15fbc9 >> dashboard link: https://syzkaller.appspot.com/bug?extid=3b9148f91b7869120e81 >> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 >> userspace arch: i386 >> >> Unfortunately, I don't have any reproducer for this issue yet. >> >> Downloadable assets: >> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-78c3925c.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/cf2bceeccde3/vmlinux-78c3925c.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/fc938dfaea6d/bzImage-78c3925c.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+3b9148f91b7869120e81@syzkaller.appspotmail.com >> >> veth_newlink+0x627/0xa10 drivers/net/veth.c:1895 >> rtnl_newlink_create net/core/rtnetlink.c:3494 [inline] >> __rtnl_newlink+0x119c/0x1960 net/core/rtnetlink.c:3714 >> rtnl_newlink+0x67/0xa0 net/core/rtnetlink.c:3727 >> rtnetlink_rcv_msg+0x3c7/0xe60 net/core/rtnetlink.c:6595 >> ------------[ cut here ]------------ >> kernel BUG at include/linux/page-flags.h:315! > > There are some more page dumping information from console: > > [ 61.367144][ T42] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888028132880 pfn:0x28130 > [ 61.371430][ T42] flags: 0xfff80000000000(node=0|zone=1|lastcpupid=0xfff) > [ 61.374455][ T42] page_type: 0xffffffff() > [ 61.376096][ T42] raw: 00fff80000000000 ffff888015ecd540 dead000000000100 0000000000000000 > [ 61.379994][ T42] raw: ffff888028132880 0000000000190000 00000000ffffffff 0000000000000000 > > Alright, the page is freed (with a refcount of 0). > >> invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI >> CPU: 1 PID: 42 Comm: kcompactd0 Not tainted 6.8.0-syzkaller-11725-g78c3925c048c #0 >> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 >> RIP: 0010:const_folio_flags+0x1bd/0x1f0 include/linux/page-flags.h:315 > > The RIP is in const_folio_flags() (called from folio_test_hugetlb()): > > VM_BUG_ON_PGFLAGS(n > 0 && !test_bit(PG_head, &page->flags), page); > > It is reasonable to WARN because the page is freed (PG_head is not set > in this case). > > The comments from folio_test_hugetlb() says "Caller should have a > reference on the folio", so the caller of PageHuge() should grab > a refcount before calling folio_test_hugetlb() since commit > 9c5ccf2db04b. But it does not mean that the @page must be a HugeTLB page > even if PageHuge(@page) returns true when the user does not hold > a extra refcount on the @page. Seems the WARN could be acceptable, so > should we remove this WARN? I am not sure. Cc more experts. Isn't this the problem Willy is fixing with the upcoing folio_test_hugetlb() changes? We cannot always grab a folio reference on hugetlb folios: free hugetlb folios have a refcount of 0. -- Cheers, David / dhildenb