syzbot


KCSAN: data-race in mas_wmb_replace / mtree_range_walk (2)

Status: moderation: reported on 2026/04/16 07:19
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+7265211618d78be5c8e2@syzkaller.appspotmail.com
First crash: 4d23h, last: 1d04h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
ed78a0ab-39ee-4c22-ac93-e5909490249b assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in mas_wmb_replace / mtree_range_walk (2) 2026/04/16 07:18 2026/04/16 07:18 2026/04/16 07:41 df15c5f3d9deb74ba8dc519449837e23f3040ac6
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in mas_wmb_replace / mtree_range_walk mm 6 566 362d 832d 0/29 auto-obsoleted due to no activity on 2025/06/12 01:09

Sample crash report:
==================================================================
BUG: KCSAN: data-race in mas_wmb_replace / mtree_range_walk

write to 0xffff888104d92e00 of 8 bytes by task 6638 on cpu 0:
 mte_set_node_dead lib/maple_tree.c:299 [inline]
 mas_put_in_tree lib/maple_tree.c:1579 [inline]
 mas_topiary_replace lib/maple_tree.c:1823 [inline]
 mas_wmb_replace+0x234/0x1760 lib/maple_tree.c:2083
 mas_wr_store_entry+0x54ff/0x5ad0 lib/maple_tree.c:-1
 mas_store_prealloc+0x43e/0x690 lib/maple_tree.c:4936
 vma_iter_store_overwrite mm/vma.h:616 [inline]
 vma_iter_store_new mm/vma.h:623 [inline]
 vma_complete+0x3c7/0x850 mm/vma.c:359
 __split_vma+0x5db/0x640 mm/vma.c:569
 split_vma mm/vma.c:599 [inline]
 vma_modify+0xbee/0xca0 mm/vma.c:1699
 vma_modify_flags+0x182/0x210 mm/vma.c:1719
 mprotect_fixup+0x3a2/0x680 mm/mprotect.c:789
 do_mprotect_pkey+0x6ae/0x960 mm/mprotect.c:967
 __do_sys_mprotect mm/mprotect.c:988 [inline]
 __se_sys_mprotect mm/mprotect.c:985 [inline]
 __x64_sys_mprotect+0x48/0x60 mm/mprotect.c:985
 x64_sys_call+0x2768/0x3020 arch/x86/include/generated/asm/syscalls_64.h:11
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888104d92e00 of 8 bytes by task 6641 on cpu 1:
 ma_dead_node lib/maple_tree.c:544 [inline]
 mtree_range_walk+0x350/0x490 lib/maple_tree.c:2051
 mas_state_walk lib/maple_tree.c:2952 [inline]
 mas_walk+0x1cc/0x370 lib/maple_tree.c:4366
 lock_vma_under_rcu+0xc9/0x210 mm/mmap_lock.c:304
 do_user_addr_fault+0x232/0x1050 arch/x86/mm/fault.c:1325
 handle_page_fault arch/x86/mm/fault.c:1474 [inline]
 exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1527
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

value changed: 0xffff8881168543c1 -> 0xffff888104d92e00

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6641 Comm: syz.7.7805 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/20 01:45 upstream c1f49dea2b8f 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wmb_replace / mtree_range_walk
2026/04/19 05:12 upstream eb5249b12507 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wmb_replace / mtree_range_walk
2026/04/18 09:29 upstream 8541d8f725c6 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wmb_replace / mtree_range_walk
2026/04/16 07:18 upstream aec2f682d47c df15c5f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wmb_replace / mtree_range_walk
* Struck through repros no longer work on HEAD.