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From: Andrew Morton <akpm@linux-foundation.org>
To: adobriyan@gmail.com, akpm@linux-foundation.org,
	bob.picco@oracle.com, dan.j.williams@intel.com,
	daniel.m.jordan@oracle.com, david@redhat.com, linux-mm@kvack.org,
	mhocko@kernel.org, mhocko@suse.com, mm-commits@vger.kernel.org,
	n-horiguchi@ah.jp.nec.com, osalvador@suse.de,
	pasha.tatashin@oracle.com, sfr@canb.auug.org.au,
	steven.sistare@oracle.com, torvalds@linux-foundation.org
Subject: [patch 03/67] fs/proc/page.c: allow inspection of last section and fix end detection
Date: Mon, 03 Feb 2020 17:33:52 -0800
Message-ID: <20200204013352.Y3nhsMQOb%akpm@linux-foundation.org> (raw)
In-Reply-To: <20200203173311.6269a8be06a05e5a4aa08a93@linux-foundation.org>

From: David Hildenbrand <david@redhat.com>
Subject: fs/proc/page.c: allow inspection of last section and fix end detection

If max_pfn does not fall onto a section boundary, it is possible to
inspect PFNs up to max_pfn, and PFNs above max_pfn, however, max_pfn
itself can't be inspected.  We can have a valid (and online) memmap at and
above max_pfn if max_pfn is not aligned to a section boundary.  The whole
early section has a memmap and is marked online.  Being able to inspect
the state of these PFNs is valuable for debugging, especially because
max_pfn can change on memory hotplug and expose these memmaps.

Also, querying page flags via "./page-types -r -a 0x144001,"
(tools/vm/page-types.c) inside a x86-64 guest with 4160MB under QEMU
results in an (almost) endless loop in user space, because the end is not
detected properly when starting after max_pfn.

Instead, let's allow to inspect all pages in the highest section and
return 0 directly if we try to access pages above that section.

While at it, check the count before adjusting it, to avoid masking user
errors.

Link: http://lkml.kernel.org/r/20191211163201.17179-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Bob Picco <bob.picco@oracle.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Steven Sistare <steven.sistare@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/page.c |   30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

--- a/fs/proc/page.c~fs-proc-pagec-allow-inspection-of-last-section-and-fix-end-detection
+++ a/fs/proc/page.c
@@ -21,6 +21,21 @@
 #define KPMMASK (KPMSIZE - 1)
 #define KPMBITS (KPMSIZE * BITS_PER_BYTE)
 
+static inline unsigned long get_max_dump_pfn(void)
+{
+#ifdef CONFIG_SPARSEMEM
+	/*
+	 * The memmap of early sections is completely populated and marked
+	 * online even if max_pfn does not fall on a section boundary -
+	 * pfn_to_online_page() will succeed on all pages. Allow inspecting
+	 * these memmaps.
+	 */
+	return round_up(max_pfn, PAGES_PER_SECTION);
+#else
+	return max_pfn;
+#endif
+}
+
 /* /proc/kpagecount - an array exposing page counts
  *
  * Each entry is a u64 representing the corresponding
@@ -29,6 +44,7 @@
 static ssize_t kpagecount_read(struct file *file, char __user *buf,
 			     size_t count, loff_t *ppos)
 {
+	const unsigned long max_dump_pfn = get_max_dump_pfn();
 	u64 __user *out = (u64 __user *)buf;
 	struct page *ppage;
 	unsigned long src = *ppos;
@@ -37,9 +53,11 @@ static ssize_t kpagecount_read(struct fi
 	u64 pcount;
 
 	pfn = src / KPMSIZE;
-	count = min_t(size_t, count, (max_pfn * KPMSIZE) - src);
 	if (src & KPMMASK || count & KPMMASK)
 		return -EINVAL;
+	if (src >= max_dump_pfn * KPMSIZE)
+		return 0;
+	count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);
 
 	while (count > 0) {
 		/*
@@ -206,6 +224,7 @@ u64 stable_page_flags(struct page *page)
 static ssize_t kpageflags_read(struct file *file, char __user *buf,
 			     size_t count, loff_t *ppos)
 {
+	const unsigned long max_dump_pfn = get_max_dump_pfn();
 	u64 __user *out = (u64 __user *)buf;
 	struct page *ppage;
 	unsigned long src = *ppos;
@@ -213,9 +232,11 @@ static ssize_t kpageflags_read(struct fi
 	ssize_t ret = 0;
 
 	pfn = src / KPMSIZE;
-	count = min_t(unsigned long, count, (max_pfn * KPMSIZE) - src);
 	if (src & KPMMASK || count & KPMMASK)
 		return -EINVAL;
+	if (src >= max_dump_pfn * KPMSIZE)
+		return 0;
+	count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);
 
 	while (count > 0) {
 		/*
@@ -251,6 +272,7 @@ static const struct file_operations proc
 static ssize_t kpagecgroup_read(struct file *file, char __user *buf,
 				size_t count, loff_t *ppos)
 {
+	const unsigned long max_dump_pfn = get_max_dump_pfn();
 	u64 __user *out = (u64 __user *)buf;
 	struct page *ppage;
 	unsigned long src = *ppos;
@@ -259,9 +281,11 @@ static ssize_t kpagecgroup_read(struct f
 	u64 ino;
 
 	pfn = src / KPMSIZE;
-	count = min_t(unsigned long, count, (max_pfn * KPMSIZE) - src);
 	if (src & KPMMASK || count & KPMMASK)
 		return -EINVAL;
+	if (src >= max_dump_pfn * KPMSIZE)
+		return 0;
+	count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);
 
 	while (count > 0) {
 		/*
_


  parent reply index

Thread overview: 95+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-04  1:33 incoming Andrew Morton
2020-02-04  1:33 ` [patch 01/67] ocfs2: fix oops when writing cloned file Andrew Morton
2020-02-04  1:33 ` [patch 02/67] mm/page_alloc.c: fix uninitialized memmaps on a partially populated last section Andrew Morton
2020-02-04  1:33 ` Andrew Morton [this message]
2020-02-04  1:33 ` [patch 04/67] mm/page_alloc.c: initialize memmap of unavailable memory directly Andrew Morton
2020-02-04  1:33 ` [patch 05/67] mm/page_alloc: fix and rework pfn handling in memmap_init_zone() Andrew Morton
2020-02-04  2:45   ` Linus Torvalds
2020-02-04  1:34 ` [patch 06/67] mm: factor out next_present_section_nr() Andrew Morton
2020-02-04  3:04   ` Linus Torvalds
2020-02-04  4:29     ` Andrew Morton
2020-02-04  8:22     ` David Hildenbrand
2020-02-04  1:34 ` [patch 07/67] mm/memmap_init: update variable name in memmap_init_zone Andrew Morton
2020-02-04  1:34 ` [patch 08/67] mm/memory_hotplug: poison memmap in remove_pfn_range_from_zone() Andrew Morton
2020-02-04  1:34 ` [patch 09/67] mm/memory_hotplug: we always have a zone in find_(smallest|biggest)_section_pfn Andrew Morton
2020-02-04  1:34 ` [patch 10/67] mm/memory_hotplug: don't check for "all holes" in shrink_zone_span() Andrew Morton
2020-02-04  1:34 ` [patch 11/67] mm/memory_hotplug: drop local variables " Andrew Morton
2020-02-04  1:34 ` [patch 12/67] mm/memory_hotplug: cleanup __remove_pages() Andrew Morton
2020-02-04  1:34 ` [patch 13/67] mm/memory_hotplug: drop valid_start/valid_end from test_pages_in_a_zone() Andrew Morton
2020-02-04  1:34 ` [patch 14/67] smp_mb__{before,after}_atomic(): update Documentation Andrew Morton
2020-02-04  1:34 ` [patch 15/67] ipc/mqueue.c: remove duplicated code Andrew Morton
2020-02-04  1:34 ` [patch 16/67] ipc/mqueue.c: update/document memory barriers Andrew Morton
2020-02-04  1:34 ` [patch 17/67] ipc/msg.c: update and document " Andrew Morton
2020-02-04  1:34 ` [patch 18/67] ipc/sem.c: document and update " Andrew Morton
2020-02-04  1:34 ` [patch 19/67] ipc/msg.c: consolidate all xxxctl_down() functions Andrew Morton
2020-02-04  1:34 ` [patch 20/67] drivers/block/null_blk_main.c: fix layout Andrew Morton
2020-02-04  1:34 ` [patch 21/67] drivers/block/null_blk_main.c: fix uninitialized var warnings Andrew Morton
2020-02-04  1:34 ` [patch 22/67] pinctrl: fix pxa2xx.c build warnings Andrew Morton
2020-02-04  1:34 ` [patch 23/67] mm: remove __krealloc Andrew Morton
2020-02-04  1:35 ` [patch 24/67] mm: add generic p?d_leaf() macros Andrew Morton
2020-02-04  1:35 ` [patch 25/67] arc: mm: add p?d_leaf() definitions Andrew Morton
2020-02-04  1:35 ` [patch 26/67] arm: " Andrew Morton
2020-02-04  1:35 ` [patch 27/67] arm64: " Andrew Morton
2020-02-04  1:35 ` [patch 28/67] mips: " Andrew Morton
2020-02-04  1:35 ` [patch 29/67] powerpc: " Andrew Morton
2020-02-04  1:35 ` [patch 30/67] riscv: " Andrew Morton
2020-02-04  1:35 ` [patch 31/67] s390: " Andrew Morton
2020-02-04  1:35 ` [patch 32/67] sparc: " Andrew Morton
2020-02-04  1:35 ` [patch 33/67] x86: " Andrew Morton
2020-02-04  1:35 ` [patch 34/67] mm: pagewalk: add p4d_entry() and pgd_entry() Andrew Morton
2020-02-04  1:35 ` [patch 35/67] mm: pagewalk: allow walking without vma Andrew Morton
2020-02-04  1:35 ` [patch 36/67] mm: pagewalk: don't lock PTEs for walk_page_range_novma() Andrew Morton
2020-02-04  1:35 ` [patch 37/67] mm: pagewalk: fix termination condition in walk_pte_range() Andrew Morton
2020-02-04  1:36 ` [patch 38/67] mm: pagewalk: add 'depth' parameter to pte_hole Andrew Morton
2020-02-04  1:36 ` [patch 39/67] x86: mm: point to struct seq_file from struct pg_state Andrew Morton
2020-02-04  1:36 ` [patch 40/67] x86: mm+efi: convert ptdump_walk_pgd_level() to take a mm_struct Andrew Morton
2020-02-04  1:36 ` [patch 41/67] x86: mm: convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Andrew Morton
2020-02-04  1:36 ` [patch 42/67] mm: add generic ptdump Andrew Morton
2020-02-04  1:36 ` [patch 43/67] x86: mm: convert dump_pagetables to use walk_page_range Andrew Morton
2020-02-04  1:36 ` [patch 44/67] arm64: mm: convert mm/dump.c to use walk_page_range() Andrew Morton
2020-02-04  1:36 ` [patch 45/67] arm64: mm: display non-present entries in ptdump Andrew Morton
2020-02-04  1:36 ` [patch 46/67] mm: ptdump: reduce level numbers by 1 in note_page() Andrew Morton
2020-02-04  1:36 ` [patch 47/67] x86: mm: avoid allocating struct mm_struct on the stack Andrew Morton
2020-02-04  1:36 ` [patch 48/67] powerpc/mmu_gather: enable RCU_TABLE_FREE even for !SMP case Andrew Morton
2020-02-04  1:36 ` [patch 49/67] mm/mmu_gather: invalidate TLB correctly on batch allocation failure and flush Andrew Morton
2020-02-04  1:36 ` [patch 50/67] asm-generic/tlb: avoid potential double flush Andrew Morton
2020-02-04  1:36 ` [patch 51/67] asm-gemeric/tlb: remove stray function declarations Andrew Morton
2020-02-04  1:36 ` [patch 52/67] asm-generic/tlb: add missing CONFIG symbol Andrew Morton
2020-02-04  1:37 ` [patch 53/67] asm-generic/tlb: rename HAVE_RCU_TABLE_FREE Andrew Morton
2020-02-04  1:37 ` [patch 54/67] asm-generic/tlb: rename HAVE_MMU_GATHER_PAGE_SIZE Andrew Morton
2020-02-04  1:37 ` [patch 55/67] asm-generic/tlb: rename HAVE_MMU_GATHER_NO_GATHER Andrew Morton
2020-02-04  1:37 ` [patch 56/67] asm-generic/tlb: provide MMU_GATHER_TABLE_FREE Andrew Morton
2020-02-04  1:37 ` [patch 57/67] proc: decouple proc from VFS with "struct proc_ops" Andrew Morton
2020-02-04  1:37 ` [patch 58/67] proc: convert everything to " Andrew Morton
2020-02-04  1:37 ` [patch 59/67] lib/string: add strnchrnul() Andrew Morton
2020-02-04  1:37 ` [patch 60/67] bitops: more BITS_TO_* macros Andrew Morton
2020-02-04  1:37 ` [patch 61/67] lib: add test for bitmap_parse() Andrew Morton
2020-02-04  1:37 ` [patch 62/67] lib: make bitmap_parse_user a wrapper on bitmap_parse Andrew Morton
2020-02-04  1:37 ` [patch 63/67] lib: rework bitmap_parse() Andrew Morton
2020-02-04  1:37 ` [patch 64/67] lib: new testcases for bitmap_parse{_user} Andrew Morton
2020-02-04  1:37 ` [patch 65/67] include/linux/cpumask.h: don't calculate length of the input string Andrew Morton
2020-02-04  1:37 ` [patch 66/67] treewide: remove redundant IS_ERR() before error code check Andrew Morton
2020-02-04  1:37 ` [patch 67/67] ARM: dma-api: fix max_pfn off-by-one error in __dma_supported() Andrew Morton
2020-02-04  2:27 ` incoming Linus Torvalds
2020-02-04  2:46   ` incoming Andrew Morton
2020-02-04  3:11     ` incoming Linus Torvalds
2020-02-14  6:26 ` mmotm 2020-02-13-22-26 uploaded Andrew Morton
2020-02-14 16:29   ` mmotm 2020-02-13-22-26 uploaded (mm/hugetlb.c) Randy Dunlap
2020-02-14 17:18     ` Mike Kravetz
2020-02-14 20:51       ` Mina Almasry
     [not found]       ` <20200214204544.231482-1-almasrymina@google.com>
2020-02-14 21:00         ` [PATCH] hugetlb: fix CONFIG_CGROUP_HUGETLB ifdefs Mina Almasry
2020-02-15  1:17           ` Randy Dunlap
2020-02-15  1:56             ` Randy Dunlap
2020-02-16 20:40               ` Mina Almasry
2020-02-16 21:03                 ` Mina Almasry
2020-02-17  2:48                   ` Randy Dunlap
2020-02-17  2:57                     ` [PATCH] hugetlb: fix <linux/hugetlb_cgroup.h> structs Randy Dunlap
2020-02-17  3:53               ` [PATCH] hugetlb: fix CONFIG_CGROUP_HUGETLB ifdefs Stephen Rothwell
2020-02-14 16:49   ` mmotm 2020-02-13-22-26 uploaded (mm/migrate.c, hugetlb_cgroup.h) Randy Dunlap
2020-02-25  3:53 ` mmotm 2020-02-24-19-53 uploaded Andrew Morton
2020-02-25  6:16   ` mmotm 2020-02-24-19-53 uploaded (init/main.c: initrd*) Randy Dunlap
2020-02-25  6:18     ` Randy Dunlap
2020-02-25  6:21       ` Randy Dunlap
2020-02-25 16:41   ` mmotm 2020-02-24-19-53 uploaded (drivers/platform/x86/intel_pmc_core.c) Randy Dunlap
2020-02-25 17:01   ` mmotm 2020-02-24-19-53 uploaded (objtool warning) Randy Dunlap
2020-02-27 21:52     ` Josh Poimboeuf

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