[syzbot] [usb?] WARNING in __fsg_is_set

syzbot <[email protected]> Mon, 03 Aug 2026 17:54:20 -0700
Newsgroups	org.kernel.vger.linux-usb,org.kernel.vger.linux-kernel
Message-ID	<[email protected]>
Hello,

syzbot found the following issue on:

HEAD commit:    3708dd948844 Merge tag 'pm-7.2-rc6' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e278c6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=d31109047baed8f3b590
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/aa997b3eeef4/disk-3708dd94.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1ab7e579d11e/vmlinux-3708dd94.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7038f45d2e15/bzImage-3708dd94.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

configfs-gadget.g1 gadget.0: common->fsg is NULL in fsg_setup at 467
------------[ cut here ]------------
1
WARNING: drivers/usb/gadget/function/f_mass_storage.c:316 at __fsg_is_set.part.0.isra.0+0x2c/0x3a drivers/usb/gadget/function/f_mass_storage.c:316, CPU#0: syz-executor/7045
Modules linked in:
CPU: 0 UID: 0 PID: 7045 Comm: syz-executor Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__fsg_is_set.part.0.isra.0+0x2c/0x3a drivers/usb/gadget/function/f_mass_storage.c:316
Code: 41 89 d4 55 48 89 f5 53 48 89 fb e8 ce c9 b5 00 48 8d bb d8 00 00 00 44 89 e1 48 89 ea 48 c7 c6 80 48 ba 8c e8 75 87 eb ff 90 <0f> 0b 90 31 c0 5b 5d 41 5c e9 86 5b 6a 0a e8 a1 c9 b5 00 4c 89 e2
RSP: 0018:ffffc90000007a50 EFLAGS: 00010082
RAX: 0000000000000000 RBX: ffff888028710c00 RCX: 0000000000000000
RDX: ffff888096b22540 RSI: ffffffff81401999 RDI: fffff52000000f3a
RBP: ffffffff8cba6580 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000102 R11: 0000000000000000 R12: 00000000000001d3
R13: ffff88802b94fce8 R14: 0000000000000000 R15: ffffc90000007de8
FS:  0000000000000000(0000) GS:ffff888123dda000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3c94bf84c0 CR3: 000000008125d000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 __fsg_is_set drivers/usb/gadget/function/f_mass_storage.c:865 [inline]
 fsg_setup.cold+0x38/0x4c drivers/usb/gadget/function/f_mass_storage.c:467
 composite_setup+0xad8/0x9290 drivers/usb/gadget/composite.c:2239
 configfs_composite_setup+0xfb/0x130 drivers/usb/gadget/configfs.c:1877
 dummy_timer+0x2045/0x36f0 drivers/usb/gadget/udc/dummy_hcd.c:1951
 __run_hrtimer kernel/time/hrtimer.c:2032 [inline]
 __hrtimer_run_queues+0x462/0x9c0 kernel/time/hrtimer.c:2096
 hrtimer_run_softirq+0x17d/0x2c0 kernel/time/hrtimer.c:2113
 handle_softirqs+0x1ea/0x9b0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x162/0x210 kernel/softirq.c:735
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:finish_task_switch.isra.0+0x2cd/0x10c0 kernel/sched/core.c:5361
Code: ab 0a 00 00 41 c7 87 20 0e 00 00 00 00 00 00 0f 1f 44 00 00 49 8d 7f 48 e8 d0 a5 e8 09 e8 6b ad 3c 00 fb 48 8d bb f8 16 00 00 <48> b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 04 02 84
RSP: 0018:ffffc90005317308 EFLAGS: 00000202
RAX: 00000000000d9725 RBX: ffff888096b22540 RCX: 0000000000000080
RDX: 0000000000000000 RSI: ffffffff8e1a7695 RDI: ffff888096b23c38
RBP: ffffc90005317360 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff888054164a80
R13: 0000000000000000 R14: ffffffff9122b4a4 R15: ffff8880b843b4c0
 context_switch kernel/sched/core.c:5513 [inline]
 __schedule+0x1264/0x6730 kernel/sched/core.c:7234
 preempt_schedule_common+0x42/0xc0 kernel/sched/core.c:7413
 preempt_schedule_thunk+0x16/0x40 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:169 [inline]
 _raw_spin_unlock+0x3e/0x50 kernel/locking/spinlock.c:190
 spin_unlock include/linux/spinlock.h:390 [inline]
 zap_pte_range mm/memory.c:1964 [inline]
 zap_pmd_range mm/memory.c:2020 [inline]
 zap_pud_range mm/memory.c:2048 [inline]
 zap_p4d_range mm/memory.c:2069 [inline]
 __zap_vma_range+0x16f7/0x4a30 mm/memory.c:2109
 unmap_vmas+0x299/0x5f0 mm/memory.c:2178
 exit_mmap+0x1ef/0xa00 mm/mmap.c:1300
 __mmput+0x12a/0x410 kernel/fork.c:1187
 mmput+0x67/0x80 kernel/fork.c:1210
 exit_mm kernel/exit.c:615 [inline]
 do_exit+0x8b1/0x2ae0 kernel/exit.c:997
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1152
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3046
 arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x139/0x6f0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x666/0x870 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb7f835e84e
Code: Unable to access opcode bytes at 0x7fb7f835e824.
RSP: 002b:00007ffc9019ebb8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e6
RAX: fffffffffffffdfc RBX: 0000555587db6500 RCX: 00007fb7f835e84e
RDX: 00007ffc9019ec10 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffc9019ec7c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000001388
R13: 00000000000927c0 R14: 0000000000208ec2 R15: 00007ffc9019ecd0
 </TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
   0:	00 00                	add    %al,(%rax)
   2:	41 c7 87 20 0e 00 00 	movl   $0x0,0xe20(%r15)
   9:	00 00 00 00
   d:	0f 1f 44 00 00       	nopl   0x0(%rax,%rax,1)
  12:	49 8d 7f 48          	lea    0x48(%r15),%rdi
  16:	e8 d0 a5 e8 09       	call   0x9e8a5eb
  1b:	e8 6b ad 3c 00       	call   0x3cad8b
  20:	fb                   	sti
  21:	48 8d bb f8 16 00 00 	lea    0x16f8(%rbx),%rdi
* 28:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax <-- trapping instruction
  2f:	fc ff df
  32:	48 89 fa             	mov    %rdi,%rdx
  35:	48 c1 ea 03          	shr    $0x3,%rdx
  39:	0f b6 04 02          	movzbl (%rdx,%rax,1),%eax
  3d:	84                   	.byte 0x84


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