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Mon, 15 Dec 2025 00:05:02 -0800 (PST) Date: Mon, 15 Dec 2025 00:05:02 -0800 In-Reply-To: X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <693fc12e.a70a0220.104cf0.0338.GAE@google.com> Subject: Re: [syzbot] [comedi?] memory leak in do_cmd_ioctl From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, xiaopei01@kylinos.cn, xiaopeitux@foxmail.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: BUG: unable to handle kernel paging request in do_cmd_ioctl BUG: unable to handle page fault for address: ffffec5e00000008 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP PTI CPU: 1 UID: 0 PID: 6735 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:page_slab mm/slab.h:142 [inline] RIP: 0010:kfree+0x6c/0x3d0 mm/slub.c:6869 Code: 80 48 01 df 0f 82 6a 03 00 00 48 c7 c0 00 00 00 80 48 2b 05 66 9b 14 05 48 01 c7 48 c1 ef 0c 48 c1 e7 06 48 03 3d 44 9b 14 05 <48> 8b 47 08 a8 01 4c 8d 60 ff 4c 0f 44 e7 41 80 7c 24 33 f5 0f 85 RSP: 0018:ffffc9000217fd50 EFLAGS: 00010286 RAX: 0000777f80000000 RBX: 00002000000000c0 RCX: ffffffff844b815c RDX: ffff8881244d9180 RSI: ffffffff844ab69a RDI: ffffec5e00000000 RBP: ffffc9000217fda0 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000010 R11: ffffffff81000130 R12: ffff8881136bc198 R13: ffff8881458db700 R14: ffff8881458db500 R15: ffffc9000217fe28 FS: 00007feb67bfe6c0(0000) GS:ffff8881b266b000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffec5e00000008 CR3: 000000010a316000 CR4: 00000000003526f0 Call Trace: do_cmd_ioctl.part.0+0x18a/0x360 drivers/comedi/comedi_fops.c:1896 do_cmd_ioctl drivers/comedi/comedi_fops.c:1858 [inline] comedi_unlocked_ioctl+0xdea/0x1300 drivers/comedi/comedi_fops.c:2321 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0xf4/0x140 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7feb6858f749 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007feb67bfe038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007feb687e5fa0 RCX: 00007feb6858f749 RDX: 0000200000000180 RSI: 0000000080506409 RDI: 0000000000000003 RBP: 00007feb68613f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007feb687e6038 R14: 00007feb687e5fa0 R15: 00007fff6cee0be8 Modules linked in: CR2: ffffec5e00000008 ---[ end trace 0000000000000000 ]--- RIP: 0010:page_slab mm/slab.h:142 [inline] RIP: 0010:kfree+0x6c/0x3d0 mm/slub.c:6869 Code: 80 48 01 df 0f 82 6a 03 00 00 48 c7 c0 00 00 00 80 48 2b 05 66 9b 14 05 48 01 c7 48 c1 ef 0c 48 c1 e7 06 48 03 3d 44 9b 14 05 <48> 8b 47 08 a8 01 4c 8d 60 ff 4c 0f 44 e7 41 80 7c 24 33 f5 0f 85 RSP: 0018:ffffc9000217fd50 EFLAGS: 00010286 RAX: 0000777f80000000 RBX: 00002000000000c0 RCX: ffffffff844b815c RDX: ffff8881244d9180 RSI: ffffffff844ab69a RDI: ffffec5e00000000 RBP: ffffc9000217fda0 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000010 R11: ffffffff81000130 R12: ffff8881136bc198 R13: ffff8881458db700 R14: ffff8881458db500 R15: ffffc9000217fe28 FS: 00007feb67bfe6c0(0000) GS:ffff8881b266b000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffec5e00000008 CR3: 000000010a316000 CR4: 00000000003526f0 ---------------- Code disassembly (best guess): 0: 80 48 01 df orb $0xdf,0x1(%rax) 4: 0f 82 6a 03 00 00 jb 0x374 a: 48 c7 c0 00 00 00 80 mov $0xffffffff80000000,%rax 11: 48 2b 05 66 9b 14 05 sub 0x5149b66(%rip),%rax # 0x5149b7e 18: 48 01 c7 add %rax,%rdi 1b: 48 c1 ef 0c shr $0xc,%rdi 1f: 48 c1 e7 06 shl $0x6,%rdi 23: 48 03 3d 44 9b 14 05 add 0x5149b44(%rip),%rdi # 0x5149b6e * 2a: 48 8b 47 08 mov 0x8(%rdi),%rax <-- trapping instruction 2e: a8 01 test $0x1,%al 30: 4c 8d 60 ff lea -0x1(%rax),%r12 34: 4c 0f 44 e7 cmove %rdi,%r12 38: 41 80 7c 24 33 f5 cmpb $0xf5,0x33(%r12) 3e: 0f .byte 0xf 3f: 85 .byte 0x85 Tested on: commit: 8f0b4cce Linux 6.19-rc1 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=16bd411a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=d60836e327fd6756 dashboard link: https://syzkaller.appspot.com/bug?extid=f238baf6ded841b5a82e compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 patch: https://syzkaller.appspot.com/x/patch.diff?x=166d411a580000