On 1/17/19 3:33 AM, syzbot wrote: > Hello> syzbot found the following crash on: > > HEAD commit: b808822a75a3 Add linux-next specific files for 20190111 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=16a471d8c00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=c052ead0aed5001b > dashboard link: https://syzkaller.appspot.com/bug?extid=80dd4798c16c634daf15 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+80dd4798c16c634daf15@xxxxxxxxxxxxxxxxxxxxxxxxx > > ------------[ cut here ]------------ > kernel BUG at mm/page_alloc.c:3112! Why does the mail subject say LINE, anyway? > invalid opcode: 0000 [#1] PREEMPT SMP KASAN > CPU: 0 PID: 1043 Comm: kcompactd0 Not tainted 5.0.0-rc1-next-20190111 #10 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > RIP: 0010:__isolate_free_page+0x4a8/0x680 mm/page_alloc.c:3112 That's BUG_ON(!PageBuddy(page)); in __isolate_free_page(). > Code: 4c 39 e3 77 c0 0f b6 8d 74 ff ff ff b8 01 00 00 00 48 d3 e0 e9 11 fd > ff ff 48 c7 c6 a0 63 52 88 4c 89 e7 e8 6a 14 10 00 0f 0b <0f> 0b 48 c7 c6 > c0 64 52 88 4c 89 e7 e8 57 14 10 00 0f 0b 48 89 cf > RSP: 0000:ffff8880a78e6f58 EFLAGS: 00010007 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88812fffc7e0 > RDX: 1ffff11025fff8fc RSI: 0000000000000007 RDI: ffff88812fffc7b0 > RBP: ffff8880a78e7018 R08: ffff8880a78ce000 R09: ffffed1014f1cdf2 > R10: ffffed1014f1cdf1 R11: 0000000000000003 R12: ffff88812fffc7b0 > R13: 1ffff11014f1cdf2 R14: ffff88812fffc7b0 R15: ffff8880a78e6ff0 > FS: 0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000438ca0 CR3: 0000000009871000 CR4: 00000000001426f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 > Call Trace: > fast_isolate_freepages mm/compaction.c:1356 [inline] Mel's new code... but might be just a victim of e.g. bad struct page initialization? > isolate_freepages mm/compaction.c:1429 [inline] > compaction_alloc+0xd05/0x2970 mm/compaction.c:1541 > unmap_and_move mm/migrate.c:1177 [inline] > migrate_pages+0x48e/0x2cc0 mm/migrate.c:1417 > compact_zone+0x2207/0x3e90 mm/compaction.c:2173 > kcompactd_do_work+0x6de/0x1200 mm/compaction.c:2564 > kcompactd+0x251/0x970 mm/compaction.c:2657 > kthread+0x357/0x430 kernel/kthread.c:247 > ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 > Modules linked in: > > ====================================================== > WARNING: possible circular locking dependency detected > 5.0.0-rc1-next-20190111 #10 Not tainted > ------------------------------------------------------ Dunno about that, but doesn't seem to be the root cause anyway. > -> #0 (console_owner){-.-.}: > lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3860 > console_lock_spinning_enable kernel/printk/printk.c:1647 [inline] > console_unlock+0x516/0x1040 kernel/printk/printk.c:2452 > vprintk_emit+0x370/0x960 kernel/printk/printk.c:1978 > vprintk_default+0x28/0x30 kernel/printk/printk.c:2005 > vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398 > printk+0xba/0xed kernel/printk/printk.c:2038 > report_bug.cold+0x11/0x5e lib/bug.c:191 > fixup_bug arch/x86/kernel/traps.c:178 [inline] > fixup_bug arch/x86/kernel/traps.c:173 [inline] > do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 > do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:290 > invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973 > __ClearPageBuddy include/linux/page-flags.h:706 [inline] So that's VM_BUG_ON_PAGE(!Page##uname(page), page); in __ClearPage##uname, so another problem with !PageBuddy. > rmv_page_order mm/page_alloc.c:744 [inline] > rmv_page_order mm/page_alloc.c:742 [inline] > __isolate_free_page+0x4a8/0x680 mm/page_alloc.c:3134 But this is later in the function than the first BUG_ON, so something has raced with us? Also two kcompactd crashes with slightly different stacktraces, that would have to be a NUMA system with multiple kcompactd's? > fast_isolate_freepages mm/compaction.c:1356 [inline] > isolate_freepages mm/compaction.c:1429 [inline] > compaction_alloc+0xd05/0x2970 mm/compaction.c:1541 > unmap_and_move mm/migrate.c:1177 [inline] > migrate_pages+0x48e/0x2cc0 mm/migrate.c:1417 > compact_zone+0x2207/0x3e90 mm/compaction.c:2173 > kcompactd_do_work+0x6de/0x1200 mm/compaction.c:2564 > kcompactd+0x251/0x970 mm/compaction.c:2657 > kthread+0x357/0x430 kernel/kthread.c:247 > ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
