From deb88a2a19e85842d79ba96b05031739ec327ff4 Mon Sep 17 00:00:00 2001 From: Toshi Kani Date: Fri, 3 Feb 2017 13:13:20 -0800 Subject: mm/memory_hotplug.c: check start_pfn in test_pages_in_a_zone() Patch series "fix a kernel oops when reading sysfs valid_zones", v2. A sysfs memory file is created for each 2GiB memory block on x86-64 when the system has 64GiB or more memory. [1] When the start address of a memory block is not backed by struct page, i.e. a memory range is not aligned by 2GiB, reading its 'valid_zones' attribute file leads to a kernel oops. This issue was observed on multiple x86-64 systems with more than 64GiB of memory. This patch-set fixes this issue. Patch 1 first fixes an issue in test_pages_in_a_zone(), which does not test the start section. Patch 2 then fixes the kernel oops by extending test_pages_in_a_zone() to return valid [start, end). Note for stable kernels: The memory block size change was made by commit bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64 systems"), which was accepted to 3.9. However, this patch-set depends on (and fixes) the change to test_pages_in_a_zone() made by commit 5f0f2887f4de ("mm/memory_hotplug.c: check for missing sections in test_pages_in_a_zone()"), which was accepted to 4.4. So, I recommend that we backport it up to 4.4. [1] 'Commit bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64 systems")' This patch (of 2): test_pages_in_a_zone() does not check 'start_pfn' when it is aligned by section since 'sec_end_pfn' is set equal to 'pfn'. Since this function is called for testing the range of a sysfs memory file, 'start_pfn' is always aligned by section. Fix it by properly setting 'sec_end_pfn' to the next section pfn. Also make sure that this function returns 1 only when the range belongs to a zone. Link: http://lkml.kernel.org/r/20170127222149.30893-2-toshi.kani@hpe.com Signed-off-by: Toshi Kani Cc: Andrew Banman Cc: Reza Arbab Cc: Greg KH Cc: [4.4+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) (limited to 'mm/memory_hotplug.c') diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index ca2723d47338..1218f73890b6 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1483,7 +1483,7 @@ bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) } /* - * Confirm all pages in a range [start, end) is belongs to the same zone. + * Confirm all pages in a range [start, end) belong to the same zone. */ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) { @@ -1491,9 +1491,9 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) struct zone *zone = NULL; struct page *page; int i; - for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn); + for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn + 1); pfn < end_pfn; - pfn = sec_end_pfn + 1, sec_end_pfn += PAGES_PER_SECTION) { + pfn = sec_end_pfn, sec_end_pfn += PAGES_PER_SECTION) { /* Make sure the memory section is present first */ if (!present_section_nr(pfn_to_section_nr(pfn))) continue; @@ -1512,7 +1512,11 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) zone = page_zone(page); } } - return 1; + + if (zone) + return 1; + else + return 0; } /* -- cgit v1.2.3 From a96dfddbcc04336bbed50dc2b24823e45e09e80c Mon Sep 17 00:00:00 2001 From: Toshi Kani Date: Fri, 3 Feb 2017 13:13:23 -0800 Subject: base/memory, hotplug: fix a kernel oops in show_valid_zones() Reading a sysfs "memoryN/valid_zones" file leads to the following oops when the first page of a range is not backed by struct page. show_valid_zones() assumes that 'start_pfn' is always valid for page_zone(). BUG: unable to handle kernel paging request at ffffea017a000000 IP: show_valid_zones+0x6f/0x160 This issue may happen on x86-64 systems with 64GiB or more memory since their memory block size is bumped up to 2GiB. [1] An example of such systems is desribed below. 0x3240000000 is only aligned by 1GiB and this memory block starts from 0x3200000000, which is not backed by struct page. BIOS-e820: [mem 0x0000003240000000-0x000000603fffffff] usable Since test_pages_in_a_zone() already checks holes, fix this issue by extending this function to return 'valid_start' and 'valid_end' for a given range. show_valid_zones() then proceeds with the valid range. [1] 'Commit bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64 systems")' Link: http://lkml.kernel.org/r/20170127222149.30893-3-toshi.kani@hpe.com Signed-off-by: Toshi Kani Cc: Greg Kroah-Hartman Cc: Zhang Zhen Cc: Reza Arbab Cc: David Rientjes Cc: Dan Williams Cc: [4.4+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) (limited to 'mm/memory_hotplug.c') diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 1218f73890b6..b8c11e063ff0 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1484,10 +1484,13 @@ bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) /* * Confirm all pages in a range [start, end) belong to the same zone. + * When true, return its valid [start, end). */ -int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) +int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn, + unsigned long *valid_start, unsigned long *valid_end) { unsigned long pfn, sec_end_pfn; + unsigned long start, end; struct zone *zone = NULL; struct page *page; int i; @@ -1509,14 +1512,20 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) page = pfn_to_page(pfn + i); if (zone && page_zone(page) != zone) return 0; + if (!zone) + start = pfn + i; zone = page_zone(page); + end = pfn + MAX_ORDER_NR_PAGES; } } - if (zone) + if (zone) { + *valid_start = start; + *valid_end = end; return 1; - else + } else { return 0; + } } /* @@ -1843,6 +1852,7 @@ static int __ref __offline_pages(unsigned long start_pfn, long offlined_pages; int ret, drain, retry_max, node; unsigned long flags; + unsigned long valid_start, valid_end; struct zone *zone; struct memory_notify arg; @@ -1853,10 +1863,10 @@ static int __ref __offline_pages(unsigned long start_pfn, return -EINVAL; /* This makes hotplug much easier...and readable. we assume this for now. .*/ - if (!test_pages_in_a_zone(start_pfn, end_pfn)) + if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start, &valid_end)) return -EINVAL; - zone = page_zone(pfn_to_page(start_pfn)); + zone = page_zone(pfn_to_page(valid_start)); node = zone_to_nid(zone); nr_pages = end_pfn - start_pfn; -- cgit v1.2.3