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

Status: upstream: reported on 2026/04/17 09:12
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+38a879f4a73497f2dfef@syzkaller.appspotmail.com
First crash: 4d10h, last: 3h37m
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
a67ccdf7-4a98-4fdc-ab7a-f77a6dbe3a96 assessment-kcsan Benign: ❌  Confident: ✅  KCSAN: data-race in mas_wr_store_entry / mtree_range_walk (2) 2026/04/16 10:01 2026/04/16 10:01 2026/04/16 10:22 df15c5f3d9deb74ba8dc519449837e23f3040ac6
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [mm?] KCSAN: data-race in mas_wr_store_entry / mtree_range_walk (2) 4 (5) 2026/04/20 19:29
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in mas_wr_store_entry / mtree_range_walk mm 6 172 363d 574d 0/29 auto-obsoleted due to no activity on 2025/06/10 11:41

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

write to 0xffff88812c7d5c08 of 8 bytes by task 25288 on cpu 1:
 mas_wr_slot_store lib/maple_tree.c:3232 [inline]
 mas_wr_store_entry+0x3405/0x5ad0 lib/maple_tree.c:3528
 mas_store_prealloc+0x43e/0x690 lib/maple_tree.c:4936
 vma_iter_store_overwrite mm/vma.h:616 [inline]
 commit_merge+0x6a1/0x720 mm/vma.c:766
 vma_expand+0x301/0x460 mm/vma.c:1219
 vma_merge_new_range+0x29c/0x320 mm/vma.c:1112
 __mmap_region mm/vma.c:2766 [inline]
 mmap_region+0x10a5/0x20d0 mm/vma.c:2856
 do_mmap+0x9b2/0xbd0 mm/mmap.c:560
 vm_mmap_pgoff+0x183/0x2d0 mm/util.c:581
 ksys_mmap_pgoff+0xc1/0x310 mm/mmap.c:606
 x64_sys_call+0x14df/0x3020 arch/x86/include/generated/asm/syscalls_64.h:10
 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 0xffff88812c7d5c08 of 8 bytes by task 25293 on cpu 0:
 mtree_range_walk+0x1a6/0x490 lib/maple_tree.c:2032
 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: 0x00007f031de34fff -> 0x00007f031de13fff

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 25293 Comm: syz.0.7220 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/20 16:53 upstream c1f49dea2b8f e65da4ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wr_store_entry / mtree_range_walk
2026/04/20 05:50 upstream c1f49dea2b8f 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wr_store_entry / mtree_range_walk
2026/04/19 22:07 upstream faeab166167f 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wr_store_entry / mtree_range_walk
2026/04/17 12:23 upstream 3cd8b194bf34 de0a551d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wr_store_entry / mtree_range_walk
2026/04/16 22:11 upstream 1d51b370a0f8 4743f87d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wr_store_entry / mtree_range_walk
2026/04/16 10:01 upstream aec2f682d47c df15c5f3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wr_store_entry / mtree_range_walk
* Struck through repros no longer work on HEAD.