------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: lib/refcount.c:28 at refcount_warn_saturate+0x10d/0x210, CPU#1: syz-executor.1/11063 Modules linked in: CPU: 1 UID: 0 PID: 11063 Comm: syz-executor.1 Not tainted 6.18.0-rc5-next-20251114 #1 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x10d/0x210 Code: 15 0c 04 31 ff 89 de e8 51 22 1f ff 84 db 75 9f e8 78 27 1f ff c6 05 0e 15 0c 04 01 90 48 c7 c7 a0 07 03 85 e8 54 43 e4 fe 90 <0f> 0b 90 90 e9 7c ff ff ff e8 55 27 1f ff 0f b6 1d e9 14 0c 04 31 RSP: 0018:ffff88801621fdb0 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc90003409000 RDX: 0000000000040000 RSI: ffffffff813a514e RDI: 0000000000000001 RBP: ffffea0001074f6c R08: 0000000000000001 R09: ffffed100d9e4849 R10: 0000000000000001 R11: 0000000000000001 R12: ffffea0001074f40 R13: ffffea0001074f6c R14: ffffffff85cfdf20 R15: ffff888016a4bff8 FS: 00007f1c0ceee700(0000) GS:ffff8880e548f000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2cf21000 CR3: 000000004bb5e000 CR4: 0000000000350ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Call Trace: nsproxy_free+0x4d3/0x5a0 create_new_namespaces+0x585/0x750 unshare_nsproxy_namespaces+0xc0/0x200 ksys_unshare+0x468/0xa10 __x64_sys_unshare+0x31/0x40 do_syscall_64+0xbf/0x430 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f1c0f999b19 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f1c0ceee188 EFLAGS: 00000246 ORIG_RAX: 0000000000000110 RAX: ffffffffffffffda RBX: 00007f1c0faad020 RCX: 00007f1c0f999b19 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000004a000080 RBP: 00007f1c0f9f3f6d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffd6d00cc4f R14: 00007f1c0ceee300 R15: 0000000000022000 irq event stamp: 10875 hardirqs last enabled at (10885): [] __up_console_sem+0x78/0x80 hardirqs last disabled at (10892): [] __up_console_sem+0x5d/0x80 softirqs last enabled at (10742): [] handle_softirqs+0x50c/0x770 softirqs last disabled at (10701): [] __irq_exit_rcu+0xc4/0x100 ---[ end trace 0000000000000000 ]--- Oops: general protection fault, probably for non-canonical address 0xdffffc000000002e: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000170-0x0000000000000177] CPU: 1 UID: 0 PID: 11063 Comm: syz-executor.1 Tainted: G W 6.18.0-rc5-next-20251114 #1 PREEMPT(voluntary) Tainted: [W]=WARN Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:nsproxy_free+0x28a/0x5a0 Code: 02 00 00 4c 8b 65 28 4d 85 e4 74 43 e8 7f 56 30 00 49 8d bc 24 78 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 f7 02 00 00 49 8b 9c 24 78 01 00 00 bf 08 00 00 RSP: 0018:ffff88801621fdc8 EFLAGS: 00010217 RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffc90003409000 RDX: 000000000000002e RSI: ffffffff8144dd61 RDI: 0000000000000174 RBP: ffff88804cfab958 R08: 0000000000000001 R09: 0000000000000001 R10: ffffffff8664ed57 R11: 0000000000000001 R12: fffffffffffffffc R13: ffff88801e928c1c R14: ffffffff85cfdf20 R15: ffff888016a4bff8 FS: 00007f1c0ceee700(0000) GS:ffff8880e548f000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2cf21000 CR3: 000000004bb5e000 CR4: 0000000000350ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Call Trace: create_new_namespaces+0x585/0x750 unshare_nsproxy_namespaces+0xc0/0x200 ksys_unshare+0x468/0xa10 __x64_sys_unshare+0x31/0x40 do_syscall_64+0xbf/0x430 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f1c0f999b19 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f1c0ceee188 EFLAGS: 00000246 ORIG_RAX: 0000000000000110 RAX: ffffffffffffffda RBX: 00007f1c0faad020 RCX: 00007f1c0f999b19 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000004a000080 RBP: 00007f1c0f9f3f6d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffd6d00cc4f R14: 00007f1c0ceee300 R15: 0000000000022000 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:nsproxy_free+0x28a/0x5a0 Code: 02 00 00 4c 8b 65 28 4d 85 e4 74 43 e8 7f 56 30 00 49 8d bc 24 78 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 f7 02 00 00 49 8b 9c 24 78 01 00 00 bf 08 00 00 RSP: 0018:ffff88801621fdc8 EFLAGS: 00010217 RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffc90003409000 RDX: 000000000000002e RSI: ffffffff8144dd61 RDI: 0000000000000174 RBP: ffff88804cfab958 R08: 0000000000000001 R09: 0000000000000001 R10: ffffffff8664ed57 R11: 0000000000000001 R12: fffffffffffffffc R13: ffff88801e928c1c R14: ffffffff85cfdf20 R15: ffff888016a4bff8 FS: 00007f1c0ceee700(0000) GS:ffff8880e548f000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2cf21000 CR3: 000000004bb5e000 CR4: 0000000000350ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 audit: type=1326 audit(1763108449.778:54): auid=0 uid=0 gid=0 ses=4 subj=system_u:system_r:kernel_t:s0 pid=11048 comm="syz-executor.7" exe="/syz-executor.7" sig=9 arch=c000003e syscall=231 compat=0 ip=0x7fdcdfcb9b19 code=0x0 loop6: detected capacity change from 0 to 136 isofs_fill_super: bread failed, dev=loop6, iso_blknum=34, block=68 audit: type=1326 audit(1763108449.875:55): auid=0 uid=0 gid=0 ses=4 subj=system_u:system_r:kernel_t:s0 pid=11102 comm="syz-executor.7" exe="/syz-executor.7" sig=9 arch=c000003e syscall=231 compat=0 ip=0x7fdcdfcb9b19 code=0x0 loop6: detected capacity change from 0 to 136 isofs_fill_super: bread failed, dev=loop6, iso_blknum=34, block=68 loop6: detected capacity change from 0 to 136 audit: type=1326 audit(1763108450.735:56): auid=0 uid=0 gid=0 ses=4 subj=system_u:system_r:kernel_t:s0 pid=11130 comm="syz-executor.7" exe="/syz-executor.7" sig=9 arch=c000003e syscall=231 compat=0 ip=0x7fdcdfcb9b19 code=0x0 isofs_fill_super: bread failed, dev=loop6, iso_blknum=34, block=68 loop6: detected capacity change from 0 to 136 isofs_fill_super: bread failed, dev=loop6, iso_blknum=34, block=68 Bluetooth: hci5: command 0x0406 tx timeout audit: type=1326 audit(1763108451.643:57): auid=0 uid=0 gid=0 ses=4 subj=system_u:system_r:kernel_t:s0 pid=11179 comm="syz-executor.7" exe="/syz-executor.7" sig=9 arch=c000003e syscall=231 compat=0 ip=0x7fdcdfcb9b19 code=0x0 faux_driver regulatory: Direct firmware load for regulatory.db failed with error -2 faux_driver regulatory: Direct firmware load for regulatory.db failed with error -2 syz-executor.0 (11237) used greatest stack depth: 23408 bytes left faux_driver regulatory: Direct firmware load for regulatory.db failed with error -2 faux_driver regulatory: Direct firmware load for regulatory.db failed with error -2 faux_driver regulatory: Direct firmware load for regulatory.db failed with error -2 faux_driver regulatory: Direct firmware load for regulatory.db failed with error -2 program syz-executor.2 is using a deprecated SCSI ioctl, please convert it to SG_IO program syz-executor.2 is using a deprecated SCSI ioctl, please convert it to SG_IO program syz-executor.2 is using a deprecated SCSI ioctl, please convert it to SG_IO program syz-executor.2 is using a deprecated SCSI ioctl, please convert it to SG_IO loop3: detected capacity change from 0 to 640 loop4: detected capacity change from 0 to 544 EXT4-fs (loop3): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback. EXT4-fs (loop4): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none. ext4 filesystem being mounted at /syzkaller-testdir175185565/syzkaller.6Efud6/394/file0 supports timestamps until 2038-01-19 (0x7fffffff) EXT4-fs (loop3): unmounting filesystem 00000000-0000-0000-0000-000000000000. EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000. loop3: detected capacity change from 0 to 640 EXT4-fs (loop3): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback. ext4 filesystem being mounted at /syzkaller-testdir175185565/syzkaller.6Efud6/395/file0 supports timestamps until 2038-01-19 (0x7fffffff) EXT4-fs (loop3): unmounting filesystem 00000000-0000-0000-0000-000000000000. loop3: detected capacity change from 0 to 640 EXT4-fs (loop3): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback. loop4: detected capacity change from 0 to 544 ext4 filesystem being mounted at /syzkaller-testdir175185565/syzkaller.6Efud6/396/file0 supports timestamps until 2038-01-19 (0x7fffffff) EXT4-fs (loop4): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none. EXT4-fs (loop3): unmounting filesystem 00000000-0000-0000-0000-000000000000. EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000. loop3: detected capacity change from 0 to 640 loop4: detected capacity change from 0 to 544 EXT4-fs (loop4): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none. EXT4-fs (loop3): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback. ext4 filesystem being mounted at /syzkaller-testdir175185565/syzkaller.6Efud6/397/file0 supports timestamps until 2038-01-19 (0x7fffffff) EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000. EXT4-fs (loop3): unmounting filesystem 00000000-0000-0000-0000-000000000000. loop4: detected capacity change from 0 to 544 EXT4-fs (loop4): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none. EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000. __nla_validate_parse: 5 callbacks suppressed netlink: 12 bytes leftover after parsing attributes in process `syz-executor.0'. netlink: 12 bytes leftover after parsing attributes in process `syz-executor.0'. netlink: 12 bytes leftover after parsing attributes in process `syz-executor.0'. netlink: 12 bytes leftover after parsing attributes in process `syz-executor.0'. netlink: 12 bytes leftover after parsing attributes in process `syz-executor.0'. ---------------- Code disassembly (best guess): 0: 02 00 add (%rax),%al 2: 00 4c 8b 65 add %cl,0x65(%rbx,%rcx,4) 6: 28 4d 85 sub %cl,-0x7b(%rbp) 9: e4 74 in $0x74,%al b: 43 e8 7f 56 30 00 rex.XB callq 0x305690 11: 49 8d bc 24 78 01 00 lea 0x178(%r12),%rdi 18: 00 19: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 20: fc ff df 23: 48 89 fa mov %rdi,%rdx 26: 48 c1 ea 03 shr $0x3,%rdx * 2a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction 2e: 0f 85 f7 02 00 00 jne 0x32b 34: 49 8b 9c 24 78 01 00 mov 0x178(%r12),%rbx 3b: 00 3c: bf .byte 0xbf 3d: 08 00 or %al,(%rax)