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From: Michal Hocko <mhocko@kernel.org>
To: Mikhail Zaslonko <zaslonko@linux.ibm.com>,
	Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
	gerald.schaefer@de.ibm.com, linux-mm@kvack.org,
	LKML <linux-kernel@vger.kernel.org>,
	Michal Hocko <mhocko@suse.com>
Subject: [PATCH 1/2] mm, memory_hotplug: is_mem_section_removable do not pass the end of a zone
Date: Mon, 28 Jan 2019 15:45:05 +0100
Message-ID: <20190128144506.15603-2-mhocko@kernel.org> (raw)
In-Reply-To: <20190128144506.15603-1-mhocko@kernel.org>

From: Michal Hocko <mhocko@suse.com>

Mikhail has reported the following VM_BUG_ON triggered when reading
sysfs removable state of a memory block:
 page:000003d082008000 is uninitialized and poisoned
 page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
 Call Trace:
 ([<0000000000385b26>] test_pages_in_a_zone+0xde/0x160)
  [<00000000008f15c4>] show_valid_zones+0x5c/0x190
  [<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:
  [<0000000000385b26>] test_pages_in_a_zone+0xde/0x160
 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
zone.

Reported-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Debugged-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 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)) {
-- 
2.20.1

From: Michal Hocko <mhocko@kernel.org>
To: Mikhail Zaslonko <zaslonko@linux.ibm.com>,
	Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
	gerald.schaefer@de.ibm.com, <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Michal Hocko <mhocko@suse.com>
Subject: [PATCH 1/2] mm, memory_hotplug: is_mem_section_removable do not pass the end of a zone
Date: Mon, 28 Jan 2019 15:45:05 +0100
Message-ID: <20190128144506.15603-2-mhocko@kernel.org> (raw)
Message-ID: <20190128144505.2G7S1gir_0P1_M3LDhMLV_OwMGsDRN_OiuJsaPyyJNg@z> (raw)
In-Reply-To: <20190128144506.15603-1-mhocko@kernel.org>

From: Michal Hocko <mhocko@suse.com>

Mikhail has reported the following VM_BUG_ON triggered when reading
sysfs removable state of a memory block:
 page:000003d082008000 is uninitialized and poisoned
 page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
 Call Trace:
 ([<0000000000385b26>] test_pages_in_a_zone+0xde/0x160)
  [<00000000008f15c4>] show_valid_zones+0x5c/0x190
  [<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:
  [<0000000000385b26>] test_pages_in_a_zone+0xde/0x160
 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
zone.

Reported-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Debugged-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 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)) {
-- 
2.20.1


  parent reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-28 14:45 [PATCH 0/2] mm, memory_hotplug: fix uninitialized pages fallouts Michal Hocko
2019-01-28 14:45 ` Michal Hocko
2019-01-28 14:45 ` Michal Hocko [this message]
2019-01-28 14:45   ` [PATCH 1/2] mm, memory_hotplug: is_mem_section_removable do not pass the end of a zone Michal Hocko
2019-01-29  9:06   ` Oscar Salvador
2019-01-29  9:12     ` Michal Hocko
2019-01-30  7:54       ` Oscar Salvador
2019-01-28 14:45 ` [PATCH 2/2] mm, memory_hotplug: test_pages_in_a_zone do not pass the end of zone Michal Hocko
2019-01-28 14:45   ` Michal Hocko
2019-01-29  9:09   ` Oscar Salvador
2019-01-29  9:13     ` Michal Hocko
2019-01-28 17:50 ` [PATCH 0/2] mm, memory_hotplug: fix uninitialized pages fallouts Andrew Morton
2019-01-28 17:50   ` Andrew Morton
2019-01-28 18:41   ` Michal Hocko
2019-01-28 18:45     ` Michal Hocko
2019-01-29 13:14 ` Gerald Schaefer
2019-01-29 13:49   ` Michal Hocko
2019-01-29 14:08     ` Gerald Schaefer
2019-01-29 17:38     ` Mikhail Gavrilov
2019-01-29 20:24       ` Michal Hocko
2019-01-29 20:56         ` Mikhail Gavrilov

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