The patch titled
Subject: thp, mm: fix crash due race in MADV_FREE handling
has been added to the -mm tree. Its filename is
thp-mm-fix-crash-due-race-in-madv_free-handling.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/thp-mm-fix-crash-due-race-in-madv_free-handling.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/thp-mm-fix-crash-due-race-in-madv_free-handling.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
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: 9818b8cde622 ("madvise_free, thp: fix madvise_free_huge_pmd return value after splitting")
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>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
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;
}
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
thp-mm-fix-crash-due-race-in-madv_free-handling.patch