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2002:a05:6820:160a:b0:6a3:6f5d:4d6c with SMTP id 006d021491bc7-6b0c5a91240mr18382545eaf.6.1786954046138; Mon, 17 Aug 2026 01:07:26 -0700 (PDT) Date: Mon, 17 Aug 2026 01:07:26 -0700 In-Reply-To: <6a82baac.10853dc7.22f513.001a.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a82c13e.f7a79266.2f965f.0022.GAE@google.com> Subject: Re: [syzbot] [usb?] general protection fault in fsg_common_set_num_buffers From: syzbot To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: dcb68831eac7 Merge tag 'block-7.2-20260815' of git://git.k.. git tree: upstream console+strace: https://syzkaller.appspot.com/x/log.txt?x=12aad6c6580000 kernel config: https://syzkaller.appspot.com/x/.config?x=1d67342c314f228d dashboard link: https://syzkaller.appspot.com/bug?extid=791be35f1fbcc85d06d7 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1033fa79580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cd949580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/616b82a1afb9/disk-dcb68831.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/4b1958ef02ef/vmlinux-dcb68831.xz kernel image: https://storage.googleapis.com/syzbot-assets/8138e3edc5b6/bzImage-dcb68831.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+791be35f1fbcc85d06d7@syzkaller.appspotmail.com Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 1 UID: 0 PID: 5606 Comm: syz-executor407 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026 RIP: 0010:fsg_common_set_num_buffers+0xad/0x340 drivers/usb/gadget/function/f_mass_storage.c:2763 Code: 42 80 3c 30 00 0f 85 52 02 00 00 48 89 6d e0 e8 99 48 2c fa be c0 0c 00 00 bf 00 40 00 00 e8 ca 6c 90 fa 48 89 ea 48 c1 ea 03 <42> 80 3c 32 00 0f 85 04 02 00 00 48 89 45 00 48 85 c0 75 95 e8 6a RSP: 0018:ffffc9000333fbc0 EFLAGS: 00010202 RAX: ffff88807ec24000 RBX: 0000000000000000 RCX: 0000000000004000 RDX: 0000000000000002 RSI: ffffffff8c600300 RDI: ffffffff8e674928 RBP: 0000000000000010 R08: 0000000000000cc0 R09: 00000000ffffffff R10: ffffed100fd85000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000010 R14: dffffc0000000000 R15: ffff88807c0b4000 FS: 000055556964e400(0000) GS:ffff888123cde000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000056020ff0f000 CR3: 00000000772e6000 CR4: 00000000003526f0 Call Trace: fsg_opts_num_buffers_store+0x168/0x1b0 drivers/usb/gadget/function/f_mass_storage.c:3452 flush_write_buffer fs/configfs/file.c:207 [inline] configfs_write_iter+0x302/0x4e0 fs/configfs/file.c:229 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x6ac/0x1050 fs/read_write.c:687 ksys_write+0x12a/0x250 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fb82a557cb9 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:00007ffc1e17d488 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000200000000000 RCX: 00007fb82a557cb9 RDX: 0000000000000002 RSI: 0000200000000000 RDI: 0000000000000003 RBP: 6769666e6f632f2e R08: 0000000000000000 R09: 00007ffc1e17d5c8 R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc1e17d5b8 R13: 0000000000000002 R14: 0000200000000008 R15: 0000000000000002 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:fsg_common_set_num_buffers+0xad/0x340 drivers/usb/gadget/function/f_mass_storage.c:2763 Code: 42 80 3c 30 00 0f 85 52 02 00 00 48 89 6d e0 e8 99 48 2c fa be c0 0c 00 00 bf 00 40 00 00 e8 ca 6c 90 fa 48 89 ea 48 c1 ea 03 <42> 80 3c 32 00 0f 85 04 02 00 00 48 89 45 00 48 85 c0 75 95 e8 6a RSP: 0018:ffffc9000333fbc0 EFLAGS: 00010202 RAX: ffff88807ec24000 RBX: 0000000000000000 RCX: 0000000000004000 RDX: 0000000000000002 RSI: ffffffff8c600300 RDI: ffffffff8e674928 RBP: 0000000000000010 R08: 0000000000000cc0 R09: 00000000ffffffff R10: ffffed100fd85000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000010 R14: dffffc0000000000 R15: ffff88807c0b4000 FS: 000055556964e400(0000) GS:ffff888123cde000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000056020ff0f000 CR3: 00000000772e6000 CR4: 00000000003526f0 ---------------- Code disassembly (best guess): 0: 42 80 3c 30 00 cmpb $0x0,(%rax,%r14,1) 5: 0f 85 52 02 00 00 jne 0x25d b: 48 89 6d e0 mov %rbp,-0x20(%rbp) f: e8 99 48 2c fa call 0xfa2c48ad 14: be c0 0c 00 00 mov $0xcc0,%esi 19: bf 00 40 00 00 mov $0x4000,%edi 1e: e8 ca 6c 90 fa call 0xfa906ced 23: 48 89 ea mov %rbp,%rdx 26: 48 c1 ea 03 shr $0x3,%rdx * 2a: 42 80 3c 32 00 cmpb $0x0,(%rdx,%r14,1) <-- trapping instruction 2f: 0f 85 04 02 00 00 jne 0x239 35: 48 89 45 00 mov %rax,0x0(%rbp) 39: 48 85 c0 test %rax,%rax 3c: 75 95 jne 0xffffffd3 3e: e8 .byte 0xe8 3f: 6a .byte 0x6a --- 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.