Hi all, While fuzzing with trinity inside a KVM tools guest running the latest -next kernel I've stumbled on the following spew: [ 4249.344788] kernel BUG at include/linux/page-flags.h:575! [ 4249.344788] invalid opcode: 0000 [#1] PREEMPT SMP KASAN [ 4249.344788] Dumping ftrace buffer: [ 4249.344788] (ftrace buffer empty) [ 4249.344788] Modules linked in: [ 4249.344788] CPU: 1 PID: 5364 Comm: trinity-c10 Not tainted 4.0.0-next-20150427-sasha-00037-ga12998c-dirty #2183 [ 4249.344788] task: ffff8801a28db000 ti: ffff88006af40000 task.ti: ffff88006af40000 [ 4249.344788] RIP: isolate_migratepages_block (include/linux/page-flags.h:575 include/linux/huge_mm.h:156 include/linux/mm_inline.h:37 mm/compaction.c:784) [ 4249.383007] RSP: 0000:ffff88006af47398 EFLAGS: 00010282 [ 4249.383007] RAX: dffffc0000000000 RBX: 00000000000305e5 RCX: 0000000000000000 [ 4249.383007] RDX: 1ffffd4000182f2f RSI: 0000000000000000 RDI: ffffea0000c17978 [ 4249.383007] RBP: ffff88006af474f8 R08: 0000000000000001 R09: 0000000000000000 [ 4249.383007] R10: ffffffffab4b2d21 R11: 0000000000000001 R12: dffffc0000000000 [ 4249.401928] R13: 0000000000000001 R14: ffffea0000c17940 R15: 0000000000030600 [ 4249.401928] FS: 00007f816da75700(0000) GS:ffff880053200000(0000) knlGS:0000000000000000 [ 4249.401928] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 4249.401928] CR2: 0000000000c73fd8 CR3: 000000006aed7000 CR4: 00000000000007e0 [ 4249.401928] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 4249.401928] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 00000000005f060a [ 4249.401928] Stack: [ 4249.401928] ffff88006af473e8 ffffffff9b26f1dc ffffffff9b26f1b0 ffff88006af476e0 [ 4249.401928] ffff8800533e2b80 ffff8800533e2b80 0000000c59a2c000 ffffed000d5e8edc [ 4249.401928] 1ffff1000d5e8e85 ffff88006af476c8 0000000000000000 00000000000305e5 [ 4249.401928] Call Trace: [ 4249.401928] compact_zone (mm/compaction.c:1113 mm/compaction.c:1347) [ 4249.401928] compact_zone_order (mm/compaction.c:1466) [ 4249.401928] try_to_compact_pages (mm/compaction.c:1526) [ 4249.401928] __alloc_pages_direct_compact (mm/page_alloc.c:2452) [ 4249.401928] __alloc_pages_nodemask (mm/page_alloc.c:2756 mm/page_alloc.c:2908) [ 4249.401928] alloc_pages_vma (mm/mempolicy.c:1991) [ 4249.401928] do_huge_pmd_anonymous_page (mm/huge_memory.c:831) [ 4249.401928] handle_mm_fault (mm/memory.c:3332 mm/memory.c:3415) [ 4249.401928] __do_page_fault (arch/x86/mm/fault.c:1235) [ 4249.401928] trace_do_page_fault (arch/x86/mm/fault.c:1327 include/linux/jump_label.h:125 include/linux/context_tracking_state.h:28 include/linux/context_tracking.h:48 arch/x86/mm/fault.c:1328) [ 4249.401928] do_async_page_fault (arch/x86/kernel/kvm.c:280) [ 4249.401928] async_page_fault (arch/x86/kernel/entry_64.S:1257) [ 4249.401928] Code: fe ff 4c 8b 9d c0 fe ff ff 4c 8b 85 c8 fe ff ff e9 bb fb ff ff 0f 1f 80 00 00 00 00 48 c7 c6 c0 31 10 a5 4c 89 c7 e8 b9 eb 00 00 <0f> 0b 0f 1f 80 00 00 00 00 e8 56 4f 90 01 48 8b b5 f0 fe ff ff All code ======== 0: fe (bad) 1: ff 4c 8b 9d decl -0x63(%rbx,%rcx,4) 5: c0 fe ff sar $0xff,%dh 8: ff 4c 8b 85 decl -0x7b(%rbx,%rcx,4) c: c8 fe ff ff enterq $0xfffe,$0xff 10: e9 bb fb ff ff jmpq 0xfffffffffffffbd0 15: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 1c: 48 c7 c6 c0 31 10 a5 mov $0xffffffffa51031c0,%rsi 23: 4c 89 c7 mov %r8,%rdi 26: e8 b9 eb 00 00 callq 0xebe4 2b:* 0f 0b ud2 <-- trapping instruction 2d: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 34: e8 56 4f 90 01 callq 0x1904f8f 39: 48 8b b5 f0 fe ff ff mov -0x110(%rbp),%rsi ... Code starting with the faulting instruction =========================================== 0: 0f 0b ud2 2: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 9: e8 56 4f 90 01 callq 0x1904f64 e: 48 8b b5 f0 fe ff ff mov -0x110(%rbp),%rsi ... [ 4249.401928] RIP isolate_migratepages_block (include/linux/page-flags.h:575 include/linux/huge_mm.h:156 include/linux/mm_inline.h:37 mm/compaction.c:784) [ 4249.401928] RSP <ffff88006af47398> Thanks, Sasha -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>