[lkml]   [2019]   [Jan]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH v2 1/2] mm, memory_hotplug: is_mem_section_removable do not pass the end of a zone
From: Michal Hocko <>

Mikhail has reported the following VM_BUG_ON triggered when reading
sysfs removable state of a memory block:
page:000003d08300c000 is uninitialized and poisoned
page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
Call Trace:
([<000000000038596c>] is_mem_section_removable+0xb4/0x190)
[<00000000008f12fa>] show_mem_removable+0x9a/0xd8
[<00000000008cf9c4>] dev_attr_show+0x34/0x70
[<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148
[<00000000003e4194>] seq_read+0x204/0x480
[<00000000003b53ea>] __vfs_read+0x32/0x178
[<00000000003b55b2>] vfs_read+0x82/0x138
[<00000000003b5be2>] ksys_read+0x5a/0xb0
[<0000000000b86ba0>] system_call+0xdc/0x2d8
Last Breaking-Event-Address:
[<000000000038596c>] is_mem_section_removable+0xb4/0x190
Kernel panic - not syncing: Fatal exception: panic_on_oops

The reason is that the memory block spans the zone boundary and we are
stumbling over an unitialized struct page. Fix this by enforcing zone
range in is_mem_section_removable so that we never run away from a

Reported-by: Mikhail Zaslonko <>
Debugged-by: Mikhail Zaslonko <>
Tested-by: Gerald Schaefer <>
Tested-by: Mikhail Gavrilov <>
Reviewed-by: Oscar Salvador <>
Signed-off-by: Michal Hocko <>
mm/memory_hotplug.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b9a667d36c55..07872789d778 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1233,7 +1233,8 @@ static bool is_pageblock_removable_nolock(struct page *page)
bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
struct page *page = pfn_to_page(start_pfn);
- struct page *end_page = page + nr_pages;
+ unsigned long end_pfn = min(start_pfn + nr_pages, zone_end_pfn(page_zone(page)));
+ struct page *end_page = pfn_to_page(end_pfn);

/* Check the starting page of each pageblock within the range */
for (; page < end_page; page = next_active_pageblock(page)) {
 \ /
  Last update: 2019-01-30 10:13    [W:0.029 / U:5.952 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site