Messages in this thread Patch in this message | | | From | David Hildenbrand <> | Subject | [PATCH v1 2/3] fs/proc/page.c: allow inspection of last section and fix end detection | Date | Mon, 9 Dec 2019 18:48:35 +0100 |
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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.
Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: Michal Hocko <mhocko@kernel.org> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: linux-fsdevel@vger.kernel.org Signed-off-by: David Hildenbrand <david@redhat.com> --- fs/proc/page.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/fs/proc/page.c b/fs/proc/page.c index e40dbfe1168e..da01d3d9999a 100644 --- a/fs/proc/page.c +++ b/fs/proc/page.c @@ -29,6 +29,7 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { + const unsigned long max_dump_pfn = round_up(max_pfn, PAGES_PER_SECTION); u64 __user *out = (u64 __user *)buf; struct page *ppage; unsigned long src = *ppos; @@ -37,9 +38,11 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf, 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) { /* @@ -208,6 +211,7 @@ 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 = round_up(max_pfn, PAGES_PER_SECTION); u64 __user *out = (u64 __user *)buf; struct page *ppage; unsigned long src = *ppos; @@ -215,9 +219,11 @@ static ssize_t kpageflags_read(struct file *file, char __user *buf, 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) { /* @@ -253,6 +259,7 @@ static const struct file_operations proc_kpageflags_operations = { static ssize_t kpagecgroup_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { + const unsigned long max_dump_pfn = round_up(max_pfn, PAGES_PER_SECTION); u64 __user *out = (u64 __user *)buf; struct page *ppage; unsigned long src = *ppos; @@ -261,9 +268,11 @@ static ssize_t kpagecgroup_read(struct file *file, char __user *buf, 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) { /* -- 2.21.0
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