UBSAN: shift-out-of-bounds in raid5_set_limits

Status: upstream: reported C repro on 2026/08/08 20:07
Subsystems: raid
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+de94ddbfff0c9e6fe030@syzkaller.appspotmail.com
First crash: 3d09h, last: 21h05m
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ID Workflow Result Correct Bug Created Started Finished Revision
4a522d4a assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ UBSAN: shift-out-of-bounds in raid5_set_limits 2026/08/09 00:15 2026/08/09 00:15 2026/08/09 00:50 5d63f80b
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[syzbot] [raid?] UBSAN: shift-out-of-bounds in raid5_set_limits 0 (1) 2026/08/08 20:07

Sample crash report:
md/raid:md0: not clean -- starting background reconstruction
md/raid:md0: device ram0 operational as raid disk 0
md/raid:md0: raid level 5 active with 1 out of 1 devices, algorithm 0
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in ./include/linux/log2.h:57:13
shift exponent 64 is too large for 64-bit type 'unsigned long'
CPU: 0 UID: 0 PID: 4920 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 dump_stack+0x1c/0x28 lib/dump_stack.c:129
 ubsan_epilogue+0x14/0x48 lib/ubsan.c:233
 __ubsan_handle_shift_out_of_bounds+0x224/0x264 lib/ubsan.c:494
 __roundup_pow_of_two include/linux/log2.h:57 [inline]
 raid5_set_limits+0x470/0x510 drivers/md/raid5.c:7835
 raid5_run+0x1554/0x1b68 drivers/md/raid5.c:8133
 md_run+0xb9c/0x1a6c drivers/md/md.c:6760
 do_md_run+0x4c/0x4e4 drivers/md/md.c:6861
 array_state_store+0x7a8/0xce8 drivers/md/md.c:-1
 md_attr_store+0x304/0x438 drivers/md/md.c:6137
 sysfs_kf_write+0xe0/0x108 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x260/0x3b8 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x51c/0xa0c fs/read_write.c:687
 ksys_write+0x12c/0x228 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __arm64_sys_write+0x84/0x98 fs/read_write.c:747
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
 el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:736
 el0t_64_sync_handler+0x48/0x148 arch/arm64/kernel/entry-common.c:755
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:594
---[ end trace ]---

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/06 00:41 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 7235a3e71949 cd5b1963 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/05 21:07 upstream c21bb4193868 1eed00d1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/07 08:44 upstream fcaeecb8b0cd c38879ea .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/06 01:55 upstream 0d8395707651 cd5b1963 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/05 20:59 upstream c21bb4193868 1eed00d1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/06 00:35 linux-next cc2b5f627e8c cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/08 04:33 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci ba5cc80fd326 e4ef95d6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/07 11:53 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci db788396cbb1 e4ef95d6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/05 20:26 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 7235a3e71949 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/05 20:26 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 7235a3e71949 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 UBSAN: shift-out-of-bounds in raid5_set_limits
2026/08/05 15:38 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 7235a3e71949 b3eac40e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 UBSAN: shift-out-of-bounds in raid5_set_limits
* Struck through repros no longer work on HEAD.