syzbot


BUG: unable to handle kernel paging request in ext4_free_ext_path

Status: upstream: reported C repro on 2026/03/25 14:06
Reported-by: syzbot+261b234ba5e4466cef19@syzkaller.appspotmail.com
First crash: 3d17h, last: 3d12h
Bug presence (1)
Date Name Commit Repro Result
2026/03/26 upstream (ToT) 0138af2472df C Failed due to an error; will retry later
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 BUG: unable to handle kernel paging request in ext4_free_ext_path origin:lts-only 8 C 4 1d21h 3d12h 0/2 upstream: reported C repro on 2026/03/25 19:29

Sample crash report:
loop0: detected capacity change from 0 to 512
EXT4-fs (loop0): mounted filesystem without journal. Quota mode: writeback.
Unable to handle kernel paging request at virtual address ffffffffffffffec
KASAN: maybe wild-memory-access in range [0x0003ffffffffff60-0x0003ffffffffff67]
Mem abort info:
  ESR = 0x0000000096000004
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x04: level 0 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000004
  CM = 0, WnR = 0
swapper pgtable: 4k pages, 48-bit VAs, pgdp=000000020dfcc000
[ffffffffffffffec] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4456 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : ext4_ext_drop_refs fs/ext4/extents.c:119 [inline]
pc : ext4_free_ext_path+0x40/0xf4 fs/ext4/extents.c:128
lr : ext4_free_ext_path+0x24/0xf4 fs/ext4/extents.c:127
sp : ffff8000211b7550
x29: ffff8000211b7550 x28: 1ffff00004236edc x27: dfff800000000000
x26: ffff700004236eb8 x25: ffff8000211b76e4 x24: ffffffffffffffe4
x23: ffff0000eaa75258 x22: dfff800000000000 x21: 0000000000000001
x20: 1ffff00004236ede x19: ffffffffffffffe4 x18: ffff800011b9bf60
x17: ffff80001835a000 x16: ffff8000082d92bc x15: ffff8000089f00b4
x14: 0000000000000001 x13: 1fffe0001d54ea4b x12: 0000000000ff0100
x11: ff00800008d173c4 x10: 0000000000000000 x9 : ffff800008d173c4
x8 : 0000000000000000 x7 : ffff80000805983c x6 : ffff800008059a4c
x5 : ffff0000d1e15ee8 x4 : ffff8000211b7040 x3 : ffff8000082d27a8
x2 : 0000000000000001 x1 : 0000000000000008 x0 : ffffffffffffffec
Call trace:
 ext4_ext_drop_refs fs/ext4/extents.c:119 [inline]
 ext4_free_ext_path+0x40/0xf4 fs/ext4/extents.c:128
 finish_range+0x200/0x2f8 fs/ext4/migrate.c:60
 ext4_ext_migrate+0x8e4/0xc08 fs/ext4/migrate.c:544
 __ext4_ioctl fs/ext4/ioctl.c:1399 [inline]
 ext4_ioctl+0x1b04/0x4328 fs/ext4/ioctl.c:1617
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: d343fc08 f2fbfff6 38f66908 35000508 (79401277) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	d343fc08 	lsr	x8, x0, #3
   4:	f2fbfff6 	movk	x22, #0xdfff, lsl #48
   8:	38f66908 	ldrsb	w8, [x8, x22]
   c:	35000508 	cbnz	w8, 0xac
* 10:	79401277 	ldrh	w23, [x19, #8] <-- trapping instruction

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/25 19:37 linux-6.1.y 1989cd3d56e2 8ee77f7d .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in ext4_free_ext_path
2026/03/25 17:20 linux-6.1.y 1989cd3d56e2 8ee77f7d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan BUG: unable to handle kernel paging request in ext4_free_ext_path
2026/03/25 16:40 linux-6.1.y 1989cd3d56e2 8ee77f7d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan BUG: unable to handle kernel paging request in ext4_free_ext_path
2026/03/25 16:26 linux-6.1.y 1989cd3d56e2 8ee77f7d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in ext4_free_ext_path
2026/03/25 15:36 linux-6.1.y 1989cd3d56e2 8ee77f7d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in ext4_free_ext_path
2026/03/25 14:07 linux-6.1.y 1989cd3d56e2 8ee77f7d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in ext4_free_ext_path
2026/03/25 14:05 linux-6.1.y 1989cd3d56e2 8ee77f7d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in ext4_free_ext_path
* Struck through repros no longer work on HEAD.