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Sat, 14 Nov 2026 20:40:32 -0800 (PST) Date: Sat, 14 Nov 2026 20:40:32 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6af937c0.094600b6.347106.0007.GAE@google.com> Subject: [syzbot] [squashfs?] general protection fault in lookup_one_qstr_excl From: syzbot To: brauner@kernel.org, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, phillip@squashfs.org.uk, squashfs-devel@lists.sourceforge.net, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 84abb955b101 Add linux-next specific files for 20261113 git tree: linux-next console+strace: https://syzkaller.appspot.com/x/log.txt?x=10a329ad580000 kernel config: https://syzkaller.appspot.com/x/.config?x=d9d5eeb0ba036071 dashboard link: https://syzkaller.appspot.com/bug?extid=03fdf84c0915fd48f361 compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12db8d3d580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=140eebfd580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/ffae1d4a717e/disk-84abb955.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/fd2a35a63abf/vmlinux-84abb955.xz kernel image: https://storage.googleapis.com/syzbot-assets/039ccf647778/bzImage-84abb955.xz mounted in repro: https://storage.googleapis.com/syzbot-assets/d95c1baa8012/mount_0.gz AI-generated root cause summary: In squashfs_lookup() (fs/squashfs/namei.c), squashfs_read_metadata() returns the positive number of bytes read on success, which is stored in err. When a subsequent squashfs_dir_space() check fails, execution branches directly to read_failure without setting err to a negative errno like -EIO, causing squashfs_lookup() to return ERR_PTR(err) where err is a positive integer (e.g., 6). The VFS caller lookup_one_qstr_excl() treats this positive pointer as a valid struct dentry pointer because IS_ERR() evaluates to false, and immediately dereferences dentry->d_flags (offset 0), causing a near-NULL pointer dereference crash. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=03fdf84c0915fd48f361 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+03fdf84c0915fd48f361@syzkaller.appspotmail.com loop0: detected capacity change from 0 to 8 SQUASHFS error: Unable to read directory block [0:26] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 UID: 0 PID: 5646 Comm: syz-executor151 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 RIP: 0010:__d_entry_type include/linux/dcache.h:452 [inline] RIP: 0010:d_is_miss include/linux/dcache.h:457 [inline] RIP: 0010:d_is_negative include/linux/dcache.h:503 [inline] RIP: 0010:lookup_one_qstr_excl+0x155/0x360 fs/namei.c:1847 Code: ff d3 48 85 c0 0f 85 8f 01 00 00 e8 a5 a6 66 ff 49 81 fe 01 f0 ff ff 72 0a e8 97 a6 66 ff e9 86 00 00 00 4c 89 f0 48 c1 e8 03 <0f> b6 04 28 84 c0 0f 85 b6 01 00 00 bd 00 00 38 00 41 23 2e 41 89 RSP: 0018:ffffc90003c57cb0 EFLAGS: 00010247 RAX: 0000000000000000 RBX: 0000000000060000 RCX: ffff8880269a1f40 RDX: 0000000000000000 RSI: 0000000000000004 RDI: 00000000ffffffff RBP: dffffc0000000000 R08: ffff88807705343b R09: 1ffff1100ee0a687 R10: dffffc0000000000 R11: ffffed100ee0a688 R12: ffff888077053380 R13: ffff888079bb7240 R14: 0000000000000006 R15: 0000000000000006 FS: 00005555603cd400(0000) GS:ffff8881233cd000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000026d50000 CR4: 00000000003526f0 Call Trace: __start_dirop fs/namei.c:2971 [inline] start_dirop fs/namei.c:2993 [inline] filename_create+0x20e/0x370 fs/namei.c:5214 filename_symlinkat+0xe8/0x430 fs/namei.c:5913 __do_sys_symlink fs/namei.c:5946 [inline] __se_sys_symlink+0x4d/0x2b0 fs/namei.c:5942 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x171/0x540 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x00007fe4baeb7c49 Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe25a11318 EFLAGS: 00000246 ORIG_RAX: 0000000000000058 RAX: ffffffffffffffda RBX: 00007ffe25a11340 RCX: 00007fe4baeb7c49 RDX: 00007fe4baeb7c49 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 00007fe4baf170b0 R08: 00005555603ce060 R09: 00005555603ce060 R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe25a11340 R13: 0000000000000002 R14: 431bde82d7b634db R15: 00007fe4baf1704b Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:__d_entry_type include/linux/dcache.h:452 [inline] RIP: 0010:d_is_miss include/linux/dcache.h:457 [inline] RIP: 0010:d_is_negative include/linux/dcache.h:503 [inline] RIP: 0010:lookup_one_qstr_excl+0x155/0x360 fs/namei.c:1847 Code: ff d3 48 85 c0 0f 85 8f 01 00 00 e8 a5 a6 66 ff 49 81 fe 01 f0 ff ff 72 0a e8 97 a6 66 ff e9 86 00 00 00 4c 89 f0 48 c1 e8 03 <0f> b6 04 28 84 c0 0f 85 b6 01 00 00 bd 00 00 38 00 41 23 2e 41 89 RSP: 0018:ffffc90003c57cb0 EFLAGS: 00010247 RAX: 0000000000000000 RBX: 0000000000060000 RCX: ffff8880269a1f40 RDX: 0000000000000000 RSI: 0000000000000004 RDI: 00000000ffffffff RBP: dffffc0000000000 R08: ffff88807705343b R09: 1ffff1100ee0a687 R10: dffffc0000000000 R11: ffffed100ee0a688 R12: ffff888077053380 R13: ffff888079bb7240 R14: 0000000000000006 R15: 0000000000000006 FS: 00005555603cd400(0000) GS:ffff8881234cd000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffe25a12000 CR3: 0000000026d50000 CR4: 00000000003526f0 ---------------- Code disassembly (best guess): 0: ff d3 call *%rbx 2: 48 85 c0 test %rax,%rax 5: 0f 85 8f 01 00 00 jne 0x19a b: e8 a5 a6 66 ff call 0xff66a6b5 10: 49 81 fe 01 f0 ff ff cmp $0xfffffffffffff001,%r14 17: 72 0a jb 0x23 19: e8 97 a6 66 ff call 0xff66a6b5 1e: e9 86 00 00 00 jmp 0xa9 23: 4c 89 f0 mov %r14,%rax 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 0f b6 04 28 movzbl (%rax,%rbp,1),%eax <-- trapping instruction 2e: 84 c0 test %al,%al 30: 0f 85 b6 01 00 00 jne 0x1ec 36: bd 00 00 38 00 mov $0x380000,%ebp 3b: 41 23 2e and (%r14),%ebp 3e: 41 rex.B 3f: 89 .byte 0x89 --- 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 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