================================================================== BUG: KFENCE: use-after-free read in dvb_device_open+0xca/0x370 drivers/media/dvb-core/dvbdev.c:99 Use-after-free read at 0xffff88823bd8ef18 (in kfence-#198): dvb_device_open+0xca/0x370 drivers/media/dvb-core/dvbdev.c:99 chrdev_open+0x5cc/0x6a0 fs/char_dev.c:414 do_dentry_open+0x8c6/0x1500 fs/open.c:929 do_open fs/namei.c:3640 [inline] path_openat+0x27f1/0x3230 fs/namei.c:3797 do_filp_open+0x1f5/0x430 fs/namei.c:3824 do_sys_openat2+0x134/0x1d0 fs/open.c:1421 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x139/0x160 fs/open.c:1447 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 kfence-#198: 0xffff88823bd8efc0-0xffff88823bd8efff, size=64, cache=page->ptl allocated by task 13242 on cpu 0 at 832.491130s: ptlock_alloc mm/memory.c:6177 [inline] ptlock_init include/linux/mm.h:2964 [inline] pmd_ptlock_init include/linux/mm.h:3064 [inline] pagetable_pmd_ctor include/linux/mm.h:3102 [inline] pmd_alloc_one include/asm-generic/pgalloc.h:137 [inline] __pmd_alloc+0x111/0x8b0 mm/memory.c:5599 pmd_alloc include/linux/mm.h:2863 [inline] __handle_mm_fault mm/memory.c:5149 [inline] handle_mm_fault+0xb5d/0x4c00 mm/memory.c:5353 do_user_addr_fault+0xac8/0x12c0 arch/x86/mm/fault.c:1322 handle_page_fault arch/x86/mm/fault.c:1463 [inline] exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608 freed by task 13242 on cpu 0 at 832.603566s: pmd_ptlock_free include/linux/mm.h:3072 [inline] pagetable_pmd_dtor include/linux/mm.h:3114 [inline] ___pmd_free_tlb+0x82/0x1a0 arch/x86/mm/pgtable.c:72 __pmd_free_tlb arch/x86/include/asm/pgalloc.h:93 [inline] free_pmd_range mm/memory.c:228 [inline] free_pud_range mm/memory.c:246 [inline] free_p4d_range mm/memory.c:280 [inline] free_pgd_range+0x86b/0xb10 mm/memory.c:360 free_pgtables+0x697/0x770 mm/memory.c:-1 exit_mmap+0x420/0xb90 mm/mmap.c:3313 __mmput+0x118/0x3c0 kernel/fork.c:1355 exit_mm+0x1f2/0x2c0 kernel/exit.c:569 do_exit+0x8dd/0x2460 kernel/exit.c:870 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024 __do_sys_exit_group kernel/exit.c:1035 [inline] __se_sys_exit_group kernel/exit.c:1033 [inline] __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1033 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 CPU: 0 PID: 13280 Comm: syz.5.1657 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 RIP: 0010:dvb_device_open+0xca/0x370 drivers/media/dvb-core/dvbdev.c:99 Code: 8b 3f 4d 85 ff 0f 84 83 01 00 00 4c 89 64 24 08 4d 8d 67 18 4c 89 e5 48 c1 ed 03 80 7c 1d 00 00 74 08 4c 89 e7 e8 06 3f dd fa <4d> 8b 2c 24 4d 85 ed 0f 84 5e 01 00 00 4c 89 e8 48 c1 e8 03 80 3c RSP: 0018:ffffc9000db577f0 EFLAGS: 00010246 RAX: 1ffffffff2ec5de7 RBX: dffffc0000000000 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000008 RDI: 00000000ffffffff RBP: 1ffff110477b1de3 R08: ffffffff8deff2ef R09: 1ffffffff1bdfe5d R10: dffffc0000000000 R11: fffffbfff1bdfe5e R12: ffff88823bd8ef18 R13: 1ffff92001b6af0c R14: ffff888026425248 R15: ffff88823bd8ef00 FS: 00007f76710c16c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff88823bd8ef18 CR3: 000000006bedd000 CR4: 00000000003506f0 DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000083 DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Call Trace: chrdev_open+0x5cc/0x6a0 fs/char_dev.c:414 do_dentry_open+0x8c6/0x1500 fs/open.c:929 do_open fs/namei.c:3640 [inline] path_openat+0x27f1/0x3230 fs/namei.c:3797 do_filp_open+0x1f5/0x430 fs/namei.c:3824 do_sys_openat2+0x134/0x1d0 fs/open.c:1421 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x139/0x160 fs/open.c:1447 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7f767015cfce Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08 RSP: 002b:00007f76710c0b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007f76710c16c0 RCX: 00007f767015cfce RDX: 0000000000000002 RSI: 00007f76710c0c00 RDI: ffffffffffffff9c RBP: 00007f76710c0c00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: cccccccccccccccd R13: 00007f7670416128 R14: 00007f7670416090 R15: 00007fff08236e08 ================================================================== ---------------- Code disassembly (best guess): 0: 8b 3f mov (%rdi),%edi 2: 4d 85 ff test %r15,%r15 5: 0f 84 83 01 00 00 je 0x18e b: 4c 89 64 24 08 mov %r12,0x8(%rsp) 10: 4d 8d 67 18 lea 0x18(%r15),%r12 14: 4c 89 e5 mov %r12,%rbp 17: 48 c1 ed 03 shr $0x3,%rbp 1b: 80 7c 1d 00 00 cmpb $0x0,0x0(%rbp,%rbx,1) 20: 74 08 je 0x2a 22: 4c 89 e7 mov %r12,%rdi 25: e8 06 3f dd fa call 0xfadd3f30 * 2a: 4d 8b 2c 24 mov (%r12),%r13 <-- trapping instruction 2e: 4d 85 ed test %r13,%r13 31: 0f 84 5e 01 00 00 je 0x195 37: 4c 89 e8 mov %r13,%rax 3a: 48 c1 e8 03 shr $0x3,%rax 3e: 80 .byte 0x80 3f: 3c .byte 0x3c