On Wed 28-06-17 13:12:49, Kirill A. Shutemov wrote: > Reinette reported following crash: > > BUG: Bad page state in process log2exe pfn:57600 > page:ffffea00015d8000 count:0 mapcount:0 mapping: (null) > index:0x20200 > flags: 0x4000000000040019(locked|uptodate|dirty|swapbacked) > raw: 4000000000040019 0000000000000000 0000000000020200 00000000ffffffff > raw: ffffea00015d8020 ffffea00015d8020 0000000000000000 0000000000000000 > page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set > bad because of flags: 0x1(locked) > Modules linked in: rfcomm 8021q bnep intel_rapl x86_pkg_temp_thermal > coretemp efivars btusb btrtl btbcm pwm_lpss_pci snd_hda_codec_hdmi btintel > pwm_lpss snd_hda_codec_realtek snd_soc_skl snd_hda_codec_generic > snd_soc_skl_ipc spi_pxa2xx_platform snd_soc_sst_ipc snd_soc_sst_dsp > i2c_designware_platform i2c_designware_core snd_hda_ext_core > snd_soc_sst_match snd_hda_intel snd_hda_codec mei_me snd_hda_core mei > snd_soc_rt286 snd_soc_rl6347a snd_soc_core efivarfs > CPU: 1 PID: 354 Comm: log2exe Not tainted 4.12.0-rc7-test-test #19 > Hardware name: Intel corporation NUC6CAYS/NUC6CAYB, BIOS > AYAPLCEL.86A.0027.2016.1108.1529 11/08/2016 > Call Trace: > dump_stack+0x95/0xeb > bad_page+0x16a/0x1f0 > free_pages_check_bad+0x117/0x190 > ? rcu_read_lock_sched_held+0xa8/0x130 > free_hot_cold_page+0x7b1/0xad0 > __put_page+0x70/0xa0 > madvise_free_huge_pmd+0x627/0x7b0 > madvise_free_pte_range+0x6f8/0x1150 > ? debug_check_no_locks_freed+0x280/0x280 > ? swapin_walk_pmd_entry+0x380/0x380 > __walk_page_range+0x6b5/0xe30 > walk_page_range+0x13b/0x310 > madvise_free_page_range.isra.16+0xad/0xd0 > ? force_swapin_readahead+0x110/0x110 > ? swapin_walk_pmd_entry+0x380/0x380 > ? lru_add_drain_cpu+0x160/0x320 > madvise_free_single_vma+0x2e4/0x470 > ? madvise_free_page_range.isra.16+0xd0/0xd0 > ? vmacache_update+0x100/0x130 > ? find_vma+0x35/0x160 > SyS_madvise+0x8ce/0x1450 > > If somebody frees the page under us and we hold the last reference to > it, put_page() would attempt to free the page before unlocking it. > > The fix is trivial reorder of operations. > > Signed-off-by: Kirill A. Shutemov <[email protected]> > Reported-by: Reinette Chatre <[email protected]> > Fixes: 9818b8cde622 ("madvise_free, thp: fix madvise_free_huge_pmd return > value after splitting") > Cc: Huang Ying <[email protected]> > Cc: Minchan Kim <[email protected]> > Cc: Dave Hansen <[email protected]>
Acked-by: Michal Hocko <[email protected]> > --- > mm/huge_memory.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 8624450f7106..25b5965c1130 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1575,8 +1575,8 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, > struct vm_area_struct *vma, > get_page(page); > spin_unlock(ptl); > split_huge_page(page); > - put_page(page); > unlock_page(page); > + put_page(page); > goto out_unlocked; > } I was about to ask what prevents get_page on an already freed page but then I've noticed that this is still under pmd_trans_huge_lock which is released right after that said get_page. -- Michal Hocko SUSE Labs
