------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 2 PID: 28760 at lib/refcount.c:25 refcount_warn_saturate+0x1ca/0x210 lib/refcount.c:25 Modules linked in: CPU: 2 PID: 28760 Comm: syz-executor.2 Not tainted 6.9.0-rc7-syzkaller-00012-gdccb07f2914c #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x1ca/0x210 lib/refcount.c:25 Code: ff 89 de e8 a8 34 10 fd 84 db 0f 85 e6 fe ff ff e8 1b 3a 10 fd c6 05 23 1d 09 0b 01 90 48 c7 c7 c0 ba 6e 8b e8 f7 ff d2 fc 90 <0f> 0b 90 90 e9 c3 fe ff ff e8 f8 39 10 fd c6 05 fe 1c 09 0b 01 90 RSP: 0018:ffffc9002a61fb58 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9002b102000 RDX: 0000000000040000 RSI: ffffffff815137c6 RDI: 0000000000000001 RBP: ffff888020d0980c R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000002 R12: ffff888020d0980c R13: dffffc0000000000 R14: 1ffff920054c3f6f R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88802c400000(0063) knlGS:00000000f5e28b40 CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 CR2: 00000000571a504c CR3: 000000005790e000 CR4: 0000000000350ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __refcount_add include/linux/refcount.h:190 [inline] __refcount_inc include/linux/refcount.h:241 [inline] refcount_inc include/linux/refcount.h:258 [inline] p9_fid_get include/net/9p/client.h:262 [inline] v9fs_fid_find+0x2e2/0x330 fs/9p/fid.c:129 v9fs_fid_lookup_with_uid fs/9p/fid.c:181 [inline] v9fs_fid_lookup+0xd8/0xf20 fs/9p/fid.c:314 v9fs_xattr_get fs/9p/xattr.c:73 [inline] v9fs_xattr_handler_get+0x36/0x130 fs/9p/xattr.c:152 __vfs_getxattr+0x13b/0x1a0 fs/xattr.c:423 cap_inode_need_killpriv+0x40/0x60 security/commoncap.c:302 security_inode_need_killpriv+0x65/0xb0 security/security.c:2504 dentry_needs_remove_privs+0xae/0x100 fs/inode.c:2015 do_truncate+0xea/0x220 fs/open.c:57 do_ftruncate+0x5e5/0x720 fs/open.c:181 __ia32_compat_sys_ftruncate+0x8a/0xe0 fs/open.c:211 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline] __do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386 do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf7257579 Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 RSP: 002b:00000000f5e285ac EFLAGS: 00000292 ORIG_RAX: 000000000000005d RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 ---------------- Code disassembly (best guess), 2 bytes skipped: 0: 10 06 adc %al,(%rsi) 2: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi 6: 10 07 adc %al,(%rdi) 8: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi c: 10 08 adc %cl,(%rax) e: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi 1e: 00 51 52 add %dl,0x52(%rcx) 21: 55 push %rbp 22: 89 e5 mov %esp,%ebp 24: 0f 34 sysenter 26: cd 80 int $0x80 * 28: 5d pop %rbp <-- trapping instruction 29: 5a pop %rdx 2a: 59 pop %rcx 2b: c3 ret 2c: 90 nop 2d: 90 nop 2e: 90 nop 2f: 90 nop 30: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi 37: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi