[moderation] [mm?] KCSAN: data-race in compaction_alloc / compaction_alloc (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 818bebeb63dd drm/xe: Don't hand out the flat CCS storage a..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17561549580000
kernel config: https://syzkaller.appspot.com/x/.config?x=947a25829226a79e
dashboard link: https://syzkaller.appspot.com/bug?extid=18d15018b6d46e76d3c8
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [ak...@linux-foundation.org brendan...@linux.dev han...@cmpxchg.org linux-...@vger.kernel.org linu...@kvack.org mho...@suse.com sur...@google.com vba...@kernel.org z...@nvidia.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/55a5d2676f16/disk-818bebeb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ee945f7ee864/vmlinux-818bebeb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c006b10822c/bzImage-818bebeb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+18d150...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in compaction_alloc / compaction_alloc

read to 0xffff88823fffab88 of 8 bytes by task 4148 on cpu 1:
update_pageblock_skip mm/compaction.c:467 [inline]
isolate_freepages mm/compaction.c:1802 [inline]
compaction_alloc_noprof mm/compaction.c:1864 [inline]
compaction_alloc+0x13b3/0x1b80 mm/compaction.c:1894
migrate_folio_unmap mm/migrate.c:1226 [inline]
migrate_pages_batch+0x371/0x1c20 mm/migrate.c:1919
migrate_pages+0x11b4/0x1890 mm/migrate.c:2140
compact_zone+0x1c99/0x2790 mm/compaction.c:2698
compact_zone_order mm/compaction.c:2820 [inline]
try_to_compact_pages+0x349/0x930 mm/compaction.c:2865
__alloc_pages_direct_compact+0xa2/0x400 mm/page_alloc.c:4185
__alloc_pages_slowpath+0x286/0x650 mm/page_alloc.c:4946
__alloc_frozen_pages_noprof+0x31d/0x400 mm/page_alloc.c:5449
alloc_pages_mpol+0xaf/0x1d0 mm/mempolicy.c:2495
alloc_frozen_pages_noprof mm/mempolicy.c:2566 [inline]
alloc_pages_noprof+0x94/0x140 mm/mempolicy.c:2586
io_mem_alloc_compound io_uring/memmap.c:42 [inline]
io_region_allocate_pages+0x12d/0x3b0 io_uring/memmap.c:188
io_create_region+0x2b0/0x330 io_uring/memmap.c:243
io_allocate_scq_urings+0x114/0x3d0 io_uring/io_uring.c:2736
io_uring_create+0x2ec/0x4f0 io_uring/io_uring.c:3041
io_uring_setup io_uring/io_uring.c:3111 [inline]
__do_sys_io_uring_setup io_uring/io_uring.c:3145 [inline]
__se_sys_io_uring_setup+0x1cb/0x1e0 io_uring/io_uring.c:3136
__x64_sys_io_uring_setup+0x31/0x40 io_uring/io_uring.c:3136
x64_sys_call+0x1fbf/0x2550 arch/x86/include/generated/asm/syscalls_64.h:426
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff88823fffab88 of 8 bytes by task 4140 on cpu 0:
update_pageblock_skip mm/compaction.c:468 [inline]
isolate_freepages mm/compaction.c:1802 [inline]
compaction_alloc_noprof mm/compaction.c:1864 [inline]
compaction_alloc+0x13e9/0x1b80 mm/compaction.c:1894
migrate_folio_unmap mm/migrate.c:1226 [inline]
migrate_pages_batch+0x371/0x1c20 mm/migrate.c:1919
migrate_pages+0x11b4/0x1890 mm/migrate.c:2140
compact_zone+0x1c99/0x2790 mm/compaction.c:2698
compact_zone_order mm/compaction.c:2820 [inline]
try_to_compact_pages+0x349/0x930 mm/compaction.c:2865
__alloc_pages_direct_compact+0xa2/0x400 mm/page_alloc.c:4185
__alloc_pages_slowpath+0x286/0x650 mm/page_alloc.c:4946
__alloc_frozen_pages_noprof+0x31d/0x400 mm/page_alloc.c:5449
alloc_buddy_frozen_folio mm/hugetlb.c:1798 [inline]
only_alloc_fresh_hugetlb_folio+0xcc/0x1e0 mm/hugetlb.c:1839
alloc_pool_huge_folio+0x2ad/0x310 mm/hugetlb.c:1897
set_max_huge_pages mm/hugetlb.c:3859 [inline]
__nr_hugepages_store_common+0x594/0xeb0 mm/hugetlb.c:4109
hugetlb_sysctl_handler_common mm/hugetlb_sysctl.c:47 [inline]
hugetlb_sysctl_handler+0x111/0x150 mm/hugetlb_sysctl.c:57
proc_sys_call_handler+0x2ec/0x4a0 fs/proc/proc_sysctl.c:600
proc_sys_write+0x22/0x30 fs/proc/proc_sysctl.c:626
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x57f/0x9a0 fs/read_write.c:687
ksys_pwrite64 fs/read_write.c:794 [inline]
__do_sys_pwrite64 fs/read_write.c:802 [inline]
__se_sys_pwrite64 fs/read_write.c:799 [inline]
__x64_sys_pwrite64+0xfd/0x150 fs/read_write.c:799
x64_sys_call+0x23be/0x2550 arch/x86/include/generated/asm/syscalls_64.h:19
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000147e00 -> 0x0000000000147200

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4140 Comm: syz.0.184 Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================


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