lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 12 Jan 2021 13:19:55 +0800
From:   Rokudo Yan <>
To:     <>
CC:     <>, <>,
        <>, <>,
        <>, <>,
        <>, <>, <>,
Subject: [PATCH] mm, compaction: make sure we isolate a valid freepage when high_pfn is used

In fast_isolate_freepages, high_pfn will be used if a prefered one(PFN >= low_fn) not found. But the high_pfn
is not reset before searching an free area, so when it was used as freepage, it may from another free area searched before.
And move_freelist_head(freelist, freepage) will have unexpected behavior(eg. corrupt the MOVABLE freelist)

Unable to handle kernel paging request at virtual address dead000000000200
Mem abort info:
  ESR = 0x96000044
  Exception class = DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
Data abort info:
  ISV = 0, ISS = 0x00000044
  CM = 0, WnR = 1
[dead000000000200] address between user and kernel address ranges

-000|compaction_alloc(?, ?)
-001|migrate_pages([NSD:0xFFFFFF80088CBBD0] from = 0xFFFFFF80088CBD88, [NSD:0xFFFFFF80088CBBC8] get_new_p
-002|compact_zone(?, [NSD:0xFFFFFF80088CBCB0] capc = 0x0)
-003|kcompactd([X19] p = 0xFFFFFF93227FBC40)
-004|kthread([X20] _create = 0xFFFFFFE1AFB26380)
---|end of frame

The issue was reported on an smart phone product with 6GB ram and 3GB zram as swap device.

This patch fixes the issue by reset high_pfn before searching each free area, which ensure
freepage and freelist match when call move_freelist_head in fast_isolate_freepages().

Fixes: 5a811889de10f1eb ("mm, compaction: use free lists to quickly locate a migration target")
 mm/compaction.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/compaction.c b/mm/compaction.c
index cc1a7f600a86..6754229f4213 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1352,6 +1352,7 @@ fast_isolate_freepages(struct compact_control *cc)
 		if (!area->nr_free)
+		high_pfn = 0;
 		spin_lock_irqsave(&cc->zone->lock, flags);
 		freelist = &area->free_list[MIGRATE_MOVABLE];
 		list_for_each_entry_reverse(freepage, freelist, lru) {

Powered by blists - more mailing lists