[patch 047/163] mm/debug: switch dump_page to get_kernel_nofault

Andrew Morton
2020-08-07T06:19:45Z

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: mm/debug: switch dump_page to get_kernel_nofault

This is simpler to use than copy_from_kernel_nofault(). Also make some of
the related error messages less verbose.

Link: http://lkml.kernel.org/r/20200709202117.7216-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/debug.c | 36 ++++++++++++++++--------------------
1 file changed, 16 insertions(+), 20 deletions(-)

--- a/mm/debug.c~mm-switch-dump_page-to-get_kernel_nofault
+++ a/mm/debug.c
@@ -115,54 +115,50 @@ void __dump_page(struct page *page, cons
else if (PageAnon(page))
type = "anon ";
else if (mapping) {
- const struct inode *host;
+ struct inode *host;
const struct address_space_operations *a_ops;
- const struct hlist_node *dentry_first;
- const struct dentry *dentry_ptr;
+ struct hlist_node *dentry_first;
+ struct dentry *dentry_ptr;
struct dentry dentry;

/*
* mapping can be invalid pointer and we don't want to crash
* accessing it, so probe everything depending on it carefully
*/
- if (copy_from_kernel_nofault(&host, &mapping->host,
- sizeof(struct inode *)) ||
- copy_from_kernel_nofault(&a_ops, &mapping->a_ops,
- sizeof(struct address_space_operations *))) {
- pr_warn("failed to read mapping->host or a_ops, mapping not a valid kernel address?\n");
+ if (get_kernel_nofault(host, &mapping->host) ||
+ get_kernel_nofault(a_ops, &mapping->a_ops)) {
+ pr_warn("failed to read mapping contents, not a valid kernel address?\n");
goto out_mapping;
}

if (!host) {
- pr_warn("mapping->a_ops:%ps\n", a_ops);
+ pr_warn("aops:%ps\n", a_ops);
goto out_mapping;
}

- if (copy_from_kernel_nofault(&dentry_first,
- &host->i_dentry.first, sizeof(struct hlist_node *))) {
- pr_warn("mapping->a_ops:%ps with invalid mapping->host inode address %px\n",
- a_ops, host);
+ if (get_kernel_nofault(dentry_first, &host->i_dentry.first)) {
+ pr_warn("aops:%ps with invalid host inode %px\n",
+ a_ops, host);
goto out_mapping;
}

if (!dentry_first) {
- pr_warn("mapping->a_ops:%ps\n", a_ops);
+ pr_warn("aops:%ps\n", a_ops);
goto out_mapping;
}

dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
- if (copy_from_kernel_nofault(&dentry, dentry_ptr,
- sizeof(struct dentry))) {
- pr_warn("mapping->aops:%ps with invalid mapping->host->i_dentry.first %px\n",
- a_ops, dentry_ptr);
+ if (get_kernel_nofault(dentry, dentry_ptr)) {
+ pr_warn("aops:%ps with invalid dentry %px\n", a_ops,
+ dentry_ptr);
} else {
/*
* if dentry is corrupted, the %pd handler may still
* crash, but it's unlikely that we reach here with a
* corrupted struct page
*/
- pr_warn("mapping->aops:%ps dentry name:\"%pd\"\n",
- a_ops, &dentry);
+ pr_warn("aops:%ps dentry name:\"%pd\"\n", a_ops,
+ &dentry);
}
}
out_mapping:
_