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From: Christian Schoenebeck To: asmadeus@codewreck.org, ericvh@kernel.org, linux-kernel@vger.kernel.org, lucho@ionkov.net, syzkaller-bugs@googlegroups.com, v9fs@lists.linux.dev, syzbot Subject: Re: [syzbot] [v9fs?] general protection fault in p9_client_walk Date: Wed, 12 Mar 2025 10:36:15 +0100 Message-ID: <34836920.9mNPFRc1x4@silver> In-Reply-To: <67d12512.050a0220.14e108.0024.GAE@google.com> References: <67d12512.050a0220.14e108.0024.GAE@google.com> Precedence: bulk X-Mailing-List: v9fs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" On Wednesday, March 12, 2025 7:09:22 AM CET syzbot wrote: > syzbot has found a reproducer for the following issue on: > > HEAD commit: 0fed89a961ea Merge tag 'hyperv-fixes-signed-20250311' of g.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=173fa654580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=f71f17a9b92472b2 > dashboard link: https://syzkaller.appspot.com/bug?extid=5b667f9a1fee4ba3775a > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=177b6874580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=138b17a8580000 > > Downloadable assets: > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-0fed89a9.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/178c4c7fb0b4/vmlinux-0fed89a9.xz > kernel image: https://storage.googleapis.com/syzbot-assets/97ef169a8fde/bzImage-0fed89a9.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+5b667f9a1fee4ba3775a@syzkaller.appspotmail.com > > Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] > CPU: 3 UID: 0 PID: 5936 Comm: syz-executor316 Not tainted 6.14.0-rc6-syzkaller-00016-g0fed89a961ea #0 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 > RIP: 0010:p9_client_walk+0x9a/0x530 net/9p/client.c:1165 > Code: 28 00 00 00 48 89 84 24 88 00 00 00 31 c0 e8 3d 44 b0 f6 48 89 d8 31 f6 48 c1 e8 03 66 89 74 24 40 48 c7 44 24 50 00 00 00 00 <42> 80 3c 30 00 0f 85 3e 04 00 00 31 ff 89 ee 4c 8b 33 e8 0f 3f b0 > RSP: 0018:ffffc9000380faa0 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001 > RDX: ffff88802a9bc880 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: 0000000000000001 R08: 0000000000000007 R09: fffffffffffff000 > R10: 0000000000000000 R11: 0000000000000002 R12: 0000000000000000 > R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff92000701f56 > FS: 000055558c345380(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f412d1932a9 CR3: 000000002107c000 CR4: 0000000000352ef0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > > clone_fid fs/9p/fid.h:23 [inline] > v9fs_fid_xattr_set+0x119/0x2d0 fs/9p/xattr.c:121 > v9fs_set_acl+0xe6/0x150 fs/9p/acl.c:276 > v9fs_set_create_acl+0x4b/0x70 fs/9p/acl.c:306 > v9fs_vfs_mkdir_dotl+0x517/0x6e0 fs/9p/vfs_inode_dotl.c:411 > vfs_mkdir+0x57d/0x860 fs/namei.c:4313 > do_mkdirat+0x301/0x3a0 fs/namei.c:4336 > __do_sys_mkdir fs/namei.c:4356 [inline] > __se_sys_mkdir fs/namei.c:4354 [inline] > __x64_sys_mkdir+0xef/0x140 fs/namei.c:4354 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f Just had a glimpse on it so far. IIUIC the trigger is in v9fs_vfs_mkdir_dotl() [fs/9p/vfs_inode_dotl.c:411] ? // NULLs out fid (since dafbe6897) v9fs_fid_add(dentry, &fid); // expects fid being non-NULL v9fs_set_create_acl(inode, fid, dacl, pacl); /Christian > RIP: 0033:0x7fd26f335429 > Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007fff6d918e28 EFLAGS: 00000246 ORIG_RAX: 0000000000000053 > RAX: ffffffffffffffda RBX: 00004000000000c0 RCX: 00007fd26f335429 > RDX: 00007fd26f335429 RSI: 0000000000000040 RDI: 00004000000000c0 > RBP: 0000000000000073 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 > R13: 00007fff6d919008 R14: 0000000000000001 R15: 0000000000000001 > > Modules linked in: > ---[ end trace 0000000000000000 ]--- > RIP: 0010:p9_client_walk+0x9a/0x530 net/9p/client.c:1165 > Code: 28 00 00 00 48 89 84 24 88 00 00 00 31 c0 e8 3d 44 b0 f6 48 89 d8 31 f6 48 c1 e8 03 66 89 74 24 40 48 c7 44 24 50 00 00 00 00 <42> 80 3c 30 00 0f 85 3e 04 00 00 31 ff 89 ee 4c 8b 33 e8 0f 3f b0 > RSP: 0018:ffffc9000380faa0 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001 > RDX: ffff88802a9bc880 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: 0000000000000001 R08: 0000000000000007 R09: fffffffffffff000 > R10: 0000000000000000 R11: 0000000000000002 R12: 0000000000000000 > R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff92000701f56 > FS: 000055558c345380(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f412d1932a9 CR3: 000000002107c000 CR4: 0000000000352ef0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > ---------------- > Code disassembly (best guess): > 0: 28 00 sub %al,(%rax) > 2: 00 00 add %al,(%rax) > 4: 48 89 84 24 88 00 00 mov %rax,0x88(%rsp) > b: 00 > c: 31 c0 xor %eax,%eax > e: e8 3d 44 b0 f6 call 0xf6b04450 > 13: 48 89 d8 mov %rbx,%rax > 16: 31 f6 xor %esi,%esi > 18: 48 c1 e8 03 shr $0x3,%rax > 1c: 66 89 74 24 40 mov %si,0x40(%rsp) > 21: 48 c7 44 24 50 00 00 movq $0x0,0x50(%rsp) > 28: 00 00 > * 2a: 42 80 3c 30 00 cmpb $0x0,(%rax,%r14,1) <-- trapping instruction > 2f: 0f 85 3e 04 00 00 jne 0x473 > 35: 31 ff xor %edi,%edi > 37: 89 ee mov %ebp,%esi > 39: 4c 8b 33 mov (%rbx),%r14 > 3c: e8 .byte 0xe8 > 3d: 0f 3f (bad) > 3f: b0 .byte 0xb0 > > > --- > 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. >