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From: Lance Yang In-Reply-To: <69babeba.050a0220.1b2d94.0003.GAE@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 71D30140008 X-Stat-Signature: qyfdia8859ptzzb3g8enjthmcnqsr5ic X-Rspam-User: X-HE-Tag: 1773852835-60593 X-HE-Meta: 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 0jV/wPhL 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/3/18 23:03, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: b84a0ebe421c Add linux-next specific files for 20260313 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=119ddd52580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=e7280ad1f68b2dce > dashboard link: https://syzkaller.appspot.com/bug?extid=de14f7701c22477db718 > compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=173b44da580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1537b8da580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/09145161a8a9/disk-b84a0ebe.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/b64c254e474c/vmlinux-b84a0ebe.xz > kernel image: https://storage.googleapis.com/syzbot-assets/a7c33f5f7f45/bzImage-b84a0ebe.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+de14f7701c22477db718@syzkaller.appspotmail.com > > Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASAN PTI Looks like it hits a general protection fault in zap_huge_pmd() while dereferencing folio->mapping via folio_test_anon() ... zap_huge_pmd() fails to handle non-present, non-none PMD entries that are not valid PMD softleaf entries, leaving folio as NULL and dereferencing it ... For PMD-sized hugetlb mappings like the reproducer above, hugetlb/userfaultfd would make such PMD entries that can be non-present and non-none without being valid PMD softleaf entries? I'll look into it :) Thanks, Lance > KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f] > CPU: 1 UID: 0 PID: 5994 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 > RIP: 0010:folio_test_anon include/linux/page-flags.h:718 [inline] > RIP: 0010:zap_huge_pmd+0x7b1/0x1030 mm/huge_memory.c:2463 > Code: 08 00 00 e8 11 e0 92 ff 48 c7 44 24 10 00 00 00 00 4c 8b 3c 24 4c 8d 75 18 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 f7 e8 f1 43 fc ff 49 8b 1e 48 89 de 48 83 > RSP: 0018:ffffc90003bb7550 EFLAGS: 00010206 > RAX: 0000000000000003 RBX: f000000000000000 RCX: dffffc0000000000 > RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000003 > RBP: 0000000000000000 R08: ffff88807cc9802f R09: 1ffff1100f993005 > R10: dffffc0000000000 R11: ffffed100f993006 R12: ffff88807cc98028 > R13: fffffffffffffa00 R14: 0000000000000018 R15: ffffc90003bb7ac0 > FS: 0000000000000000(0000) GS:ffff888124ee0000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00002000000000c0 CR3: 000000000e94a000 CR4: 00000000003526f0 > Call Trace: > > zap_pmd_range mm/memory.c:1990 [inline] > zap_pud_range mm/memory.c:2032 [inline] > zap_p4d_range mm/memory.c:2053 [inline] > __zap_vma_range+0xa82/0x4bd0 mm/memory.c:2093 > unmap_vmas+0x379/0x530 mm/memory.c:2162 > exit_mmap+0x280/0xa10 mm/mmap.c:1302 > __mmput+0x118/0x430 kernel/fork.c:1180 > exit_mm+0x18e/0x250 kernel/exit.c:581 > do_exit+0x8b9/0x2490 kernel/exit.c:962 > do_group_exit+0x21b/0x2d0 kernel/exit.c:1116 > __do_sys_exit_group kernel/exit.c:1127 [inline] > __se_sys_exit_group kernel/exit.c:1125 [inline] > __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1125 > x64_sys_call+0x221a/0x2240 arch/x86/include/generated/asm/syscalls_64.h:232 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7fdd0b39c799 > Code: Unable to access opcode bytes at 0x7fdd0b39c76f. > RSP: 002b:00007fff630f1d78 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fdd0b39c799 > RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: 0000000000000003 R08: 0000000000000000 R09: 00007fdd0b5e63e0 > R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000 > R13: 00007fdd0b5e63e0 R14: 0000000000000003 R15: 00007fff630f1e30 > > Modules linked in: > ---[ end trace 0000000000000000 ]--- > RIP: 0010:folio_test_anon include/linux/page-flags.h:718 [inline] > RIP: 0010:zap_huge_pmd+0x7b1/0x1030 mm/huge_memory.c:2463 > Code: 08 00 00 e8 11 e0 92 ff 48 c7 44 24 10 00 00 00 00 4c 8b 3c 24 4c 8d 75 18 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 f7 e8 f1 43 fc ff 49 8b 1e 48 89 de 48 83 > RSP: 0018:ffffc90003bb7550 EFLAGS: 00010206 > RAX: 0000000000000003 RBX: f000000000000000 RCX: dffffc0000000000 > RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000003 > RBP: 0000000000000000 R08: ffff88807cc9802f R09: 1ffff1100f993005 > R10: dffffc0000000000 R11: ffffed100f993006 R12: ffff88807cc98028 > R13: fffffffffffffa00 R14: 0000000000000018 R15: ffffc90003bb7ac0 > FS: 0000000000000000(0000) GS:ffff888124ee0000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00002000000000c0 CR3: 000000000e94a000 CR4: 00000000003526f0 > ---------------- > Code disassembly (best guess): > 0: 08 00 or %al,(%rax) > 2: 00 e8 add %ch,%al > 4: 11 e0 adc %esp,%eax > 6: 92 xchg %eax,%edx > 7: ff 48 c7 decl -0x39(%rax) > a: 44 24 10 rex.R and $0x10,%al > d: 00 00 add %al,(%rax) > f: 00 00 add %al,(%rax) > 11: 4c 8b 3c 24 mov (%rsp),%r15 > 15: 4c 8d 75 18 lea 0x18(%rbp),%r14 > 19: 4c 89 f0 mov %r14,%rax > 1c: 48 c1 e8 03 shr $0x3,%rax > 20: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx > 27: fc ff df > * 2a: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1) <-- trapping instruction > 2e: 74 08 je 0x38 > 30: 4c 89 f7 mov %r14,%rdi > 33: e8 f1 43 fc ff call 0xfffc4429 > 38: 49 8b 1e mov (%r14),%rbx > 3b: 48 89 de mov %rbx,%rsi > 3e: 48 rex.W > 3f: 83 .byte 0x83 > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup