From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f70.google.com (mail-ot1-f70.google.com [209.85.210.70]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8C6F1261B70 for ; Wed, 5 Aug 2026 14:01:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785938492; cv=none; b=s8RYG4I2JqXazwa6bG2JuO0HNT2GZyVR1HxL6phkcto9GURUezvVyyDTtNdn2crH7QBeuwOcZUa8OPgpUx23X9P4+/p/z+JZogNVbcs4naIArQ5fxNXSgxEqoVGnyBBfiA9LpqxJcmPELflh/J6RPv17+0OwccktFbLRPfClEPU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785938492; c=relaxed/simple; bh=k2fhYxdCRfpecQ2myWXJI5lz9KYdQfTTJ3HbH5BTX4s=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; 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2002:a4a:e841:0:b0:6a3:8738:4106 with SMTP id 006d021491bc7-6ae96f22d3fmr3721052eaf.26.1785938489456; Wed, 05 Aug 2026 07:01:29 -0700 (PDT) Date: Wed, 05 Aug 2026 07:01:29 -0700 In-Reply-To: <6a0c5f2c.a00a0220.2c7954.0000.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a734239.d1b4d54b.5552d.001c.GAE@google.com> Subject: Re: [syzbot] [kvm?] [kvm-x86?] KASAN: use-after-free Read in kvm_xen_shared_info_init From: syzbot To: aha310510@gmail.com, bp@alien8.de, dave.hansen@linux.intel.com, dwmw2@infradead.org, dwmw@amazon.co.uk, halves@igalia.com, hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, paul@xen.org, pbonzini@redhat.com, pdurrant@amazon.com, seanjc@google.com, souradiptodas6@gmail.com, stable@vger.kernel.org, syzkaller-bugs@googlegroups.com, tglx@kernel.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: c21bb4193868 Merge tag 'for_linus' of git://git.kernel.org.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=12ceecc6580000 kernel config: https://syzkaller.appspot.com/x/.config?x=145fa60d73086782 dashboard link: https://syzkaller.appspot.com/bug?extid=0948c82180d475ad24e2 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16080e49580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0948c82180d475ad24e2@syzkaller.appspotmail.com ================================================================== BUG: KASAN: use-after-free in kvm_xen_shared_info_init+0x3c6/0x440 arch/x86/kvm/xen.c:90 Read of size 4 at addr ffff8880719c4900 by task syz.4.159/7379 CPU: 0 UID: 0 PID: 7379 Comm: syz.4.159 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0x13d/0x4b0 mm/kasan/report.c:482 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595 kvm_xen_shared_info_init+0x3c6/0x440 arch/x86/kvm/xen.c:90 kvm_xen_hvm_set_attr+0xcef/0x16a0 arch/x86/kvm/xen.c:806 kvm_arch_vm_ioctl+0x2a0/0x18d0 arch/x86/kvm/x86.c:7514 kvm_vm_ioctl+0x1560/0x4180 virt/kvm/kvm_main.c:5381 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f11c5d9e019 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f11c6d15028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f11c6026090 RCX: 00007f11c5d9e019 RDX: 0000200000000840 RSI: 000000004048aec9 RDI: 0000000000000004 RBP: 00007f11c5e3500c R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f11c6026128 R14: 00007f11c6026090 R15: 00007ffd79c7b7b8 The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xe pfn:0x719c4 flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000000000 ffffea0001865f08 ffff8880b84414b0 0000000000000000 raw: 000000000000000e 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as freed page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 7379, tgid 7374 (syz.4.159), ts 201002456742, free_ts 201021576054 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1859 prep_new_page mm/page_alloc.c:1867 [inline] get_page_from_freelist+0xf48/0x3530 mm/page_alloc.c:3946 __alloc_frozen_pages_noprof+0x299/0x2dc0 mm/page_alloc.c:5304 alloc_pages_mpol+0x1fb/0x540 mm/mempolicy.c:2490 folio_alloc_mpol_noprof+0x36/0x260 mm/mempolicy.c:2509 shmem_alloc_folio+0x135/0x160 mm/shmem.c:1917 shmem_alloc_and_add_folio+0x371/0xd40 mm/shmem.c:1959 shmem_get_folio_gfp+0x6ad/0x1910 mm/shmem.c:2512 shmem_fault+0x1f9/0xa20 mm/shmem.c:2713 __do_fault+0x10b/0x440 mm/memory.c:5425 do_shared_fault mm/memory.c:5924 [inline] do_fault+0x2db/0x1750 mm/memory.c:5998 do_pte_missing mm/memory.c:4566 [inline] handle_pte_fault mm/memory.c:6379 [inline] __handle_mm_fault+0x187d/0x2a00 mm/memory.c:6517 handle_mm_fault+0x37b/0xa30 mm/memory.c:6686 faultin_page mm/gup.c:1126 [inline] __get_user_pages+0x1178/0x32a0 mm/gup.c:1428 __get_user_pages_locked mm/gup.c:1752 [inline] get_user_pages_unlocked+0x30a/0x7d0 mm/gup.c:2681 hva_to_pfn_slow virt/kvm/kvm_main.c:2903 [inline] hva_to_pfn+0x871/0xd60 virt/kvm/kvm_main.c:2999 page last free pid 7379 tgid 7374 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1406 [inline] __free_frozen_pages+0x79f/0x1090 mm/page_alloc.c:2950 __folio_put+0x3b4/0x5f0 mm/swap.c:112 folio_put include/linux/mm.h:2124 [inline] put_page include/linux/mm.h:2193 [inline] kvm_release_page_clean virt/kvm/kvm_main.c:2813 [inline] kvm_release_page_clean+0x1dc/0x250 virt/kvm/kvm_main.c:2807 hva_to_pfn_retry virt/kvm/pfncache.c:246 [inline] __kvm_gpc_refresh+0x1a63/0x22d0 virt/kvm/pfncache.c:330 __kvm_gpc_activate+0x2ab/0x490 virt/kvm/pfncache.c:424 kvm_gpc_activate_hva+0x73/0xa0 virt/kvm/pfncache.c:444 kvm_xen_hvm_set_attr+0x395/0x16a0 arch/x86/kvm/xen.c:798 kvm_arch_vm_ioctl+0x2a0/0x18d0 arch/x86/kvm/x86.c:7514 kvm_vm_ioctl+0x1560/0x4180 virt/kvm/kvm_main.c:5381 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff8880719c4800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff8880719c4880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff8880719c4900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff8880719c4980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff8880719c4a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== --- 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.