lkml.org 
[lkml]   [2019]   [Apr]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5.0 129/146] mm/debug.c: fix __dump_page when mapping->host is not set
Date
5.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oscar Salvador <osalvador@suse.de>

commit 5ae2efb1dea9f537453e841714e3ee2757595aec upstream.

While debugging something, I added a dump_page() into do_swap_page(),
and I got the splat from below. The issue happens when dereferencing
mapping->host in __dump_page():

...
else if (mapping) {
pr_warn("%ps ", mapping->a_ops);
if (mapping->host->i_dentry.first) {
struct dentry *dentry;
dentry = container_of(mapping->host->i_dentry.first, struct dentry, d_u.d_alias);
pr_warn("name:\"%pd\" ", dentry);
}
}
...

Swap address space does not contain an inode information, and so
mapping->host equals NULL.

Although the dump_page() call was added artificially into
do_swap_page(), I am not sure if we can hit this from any other path, so
it looks worth fixing it. We can easily do that by checking
mapping->host first.

Link: http://lkml.kernel.org/r/20190318072931.29094-1-osalvador@suse.de
Fixes: 1c6fb1d89e73c ("mm: print more information about mapping in __dump_page")
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/debug.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/debug.c
+++ b/mm/debug.c
@@ -79,7 +79,7 @@ void __dump_page(struct page *page, cons
pr_warn("ksm ");
else if (mapping) {
pr_warn("%ps ", mapping->a_ops);
- if (mapping->host->i_dentry.first) {
+ if (mapping->host && mapping->host->i_dentry.first) {
struct dentry *dentry;
dentry = container_of(mapping->host->i_dentry.first, struct dentry, d_u.d_alias);
pr_warn("name:\"%pd\" ", dentry);

\
 
 \ /
  Last update: 2019-04-01 19:13    [W:0.384 / U:4.940 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site