From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Subject: thp, mm: fix crash due race in MADV_FREE handling 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. Dave said: : I came up with the exact same patch. For posterity, here's the test : case, generated by syzkaller and trimmed down by Reinette: : : https://www.sr71.net/~dave/intel/log2.c : : And the config that helps detect this: : : https://www.sr71.net/~dave/intel/config-log2 Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called") Link: http://lkml.kernel.org/r/20170628101249.17879-1-kirill.shutemov@xxxxxxxxxxxxxxx Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reported-by: Reinette Chatre <reinette.chatre@xxxxxxxxx> Acked-by: Dave Hansen <dave.hansen@xxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Acked-by: Minchan Kim <minchan@xxxxxxxxxx> Cc: Huang Ying <ying.huang@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/huge_memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN mm/huge_memory.c~thp-mm-fix-crash-due-race-in-madv_free-handling mm/huge_memory.c --- a/mm/huge_memory.c~thp-mm-fix-crash-due-race-in-madv_free-handling +++ a/mm/huge_memory.c @@ -1575,8 +1575,8 @@ bool madvise_free_huge_pmd(struct mmu_ga get_page(page); spin_unlock(ptl); split_huge_page(page); - put_page(page); unlock_page(page); + put_page(page); goto out_unlocked; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
