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owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 26 Sept 2025 at 08:44, syzbot wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: cec1e6e5d1ab Merge tag 'sched_ext-for-6.17-rc7-fixes' of g.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=145d4f12580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd > dashboard link: https://syzkaller.appspot.com/bug?extid=60192c8877d0bc92a92b > compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/10b7c8fdfdec/disk-cec1e6e5.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/cbecc36962db/vmlinux-cec1e6e5.xz > kernel image: https://storage.googleapis.com/syzbot-assets/214f107d0a3e/bzImage-cec1e6e5.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+60192c8877d0bc92a92b@syzkaller.appspotmail.com > > ================================================================== > BUG: KCSAN: data-race in try_to_migrate_one / zap_page_range_single_batched > > write to 0xffff88810adfd798 of 8 bytes by task 13594 on cpu 1: > update_hiwater_rss include/linux/mm.h:2657 [inline] > try_to_migrate_one+0x918/0x16e0 mm/rmap.c:2455 > __rmap_walk_file+0x1ec/0x2b0 mm/rmap.c:2905 > try_to_migrate+0x1db/0x210 mm/rmap.c:-1 > migrate_folio_unmap mm/migrate.c:1324 [inline] > migrate_pages_batch+0x6e1/0x1ae0 mm/migrate.c:1873 > migrate_pages_sync mm/migrate.c:1996 [inline] > migrate_pages+0xf5f/0x1770 mm/migrate.c:2105 > do_mbind mm/mempolicy.c:1539 [inline] > kernel_mbind mm/mempolicy.c:1682 [inline] > __do_sys_mbind mm/mempolicy.c:1756 [inline] > __se_sys_mbind+0x975/0xac0 mm/mempolicy.c:1752 > __x64_sys_mbind+0x78/0x90 mm/mempolicy.c:1752 > x64_sys_call+0x2932/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:238 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > write to 0xffff88810adfd798 of 8 bytes by task 13595 on cpu 0: > update_hiwater_rss include/linux/mm.h:2657 [inline] > zap_page_range_single_batched+0x182/0x450 mm/memory.c:2007 > zap_page_range_single mm/memory.c:2041 [inline] > unmap_mapping_range_vma mm/memory.c:4020 [inline] > unmap_mapping_range_tree+0xfd/0x160 mm/memory.c:4037 > unmap_mapping_pages mm/memory.c:4103 [inline] > unmap_mapping_range+0xe4/0xf0 mm/memory.c:4140 > shmem_fallocate+0x262/0x840 mm/shmem.c:3746 > vfs_fallocate+0x3b6/0x400 fs/open.c:342 > madvise_remove mm/madvise.c:1049 [inline] > madvise_vma_behavior+0x192d/0x1cf0 mm/madvise.c:1346 > madvise_walk_vmas mm/madvise.c:1669 [inline] > madvise_do_behavior+0x5b7/0x970 mm/madvise.c:1885 > do_madvise+0x10e/0x190 mm/madvise.c:1978 > __do_sys_madvise mm/madvise.c:1987 [inline] > __se_sys_madvise mm/madvise.c:1985 [inline] > __x64_sys_madvise+0x64/0x80 mm/madvise.c:1985 > x64_sys_call+0x1f1a/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:29 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > value changed: 0x0000000000001645 -> 0x0000000000002165 One of these writes is getting lost. Which means highwater_rss is lossy/approximate - does it matter?