The patch titled
Subject: mm: teach dump_page() to correctly output poisoned struct pages
has been added to the -mm tree. Its filename is
mm-teach-dump_page-to-correctly-output-poisoned-struct-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-teach-dump_page-to-correctly-output-poisoned-struct-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-teach-dump_page-to-correctly-output-poisoned-struct-pages.patch
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The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Subject: mm: teach dump_page() to correctly output poisoned struct pages
If struct page is poisoned, and uninitialized access is detected via
PF_POISONED_CHECK(page) dump_page() is called to output the page. But,
the dump_page() itself accesses struct page to determine how to print it,
and therefore gets into a recursive loop.
For example:
dump_page()
__dump_page()
PageSlab(page)
PF_POISONED_CHECK(page)
VM_BUG_ON_PGFLAGS(PagePoisoned(page), page)
dump_page() recursion loop.
Link: http://lkml.kernel.org/r/20180702180536.2552-1-pasha.tatashin@xxxxxxxxxx
Fixes: f165b378bbdf ("mm: uninitialized struct page poisoning sanity checking")
Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/debug.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff -puN mm/debug.c~mm-teach-dump_page-to-correctly-output-poisoned-struct-pages mm/debug.c
--- a/mm/debug.c~mm-teach-dump_page-to-correctly-output-poisoned-struct-pages
+++ a/mm/debug.c
@@ -43,12 +43,25 @@ const struct trace_print_flags vmaflag_n
void __dump_page(struct page *page, const char *reason)
{
+ bool page_poisoned = PagePoisoned(page);
+ int mapcount;
+
+ /*
+ * If struct page is poisoned don't access Page*() functions as that
+ * leads to recursive loop. Page*() check for poisoned pages, and calls
+ * dump_page() when detected.
+ */
+ if (page_poisoned) {
+ pr_emerg("page:%px is uninitialized and poisoned", page);
+ goto hex_only;
+ }
+
/*
* Avoid VM_BUG_ON() in page_mapcount().
* page->_mapcount space in struct page is used by sl[aou]b pages to
* encode own info.
*/
- int mapcount = PageSlab(page) ? 0 : page_mapcount(page);
+ mapcount = PageSlab(page) ? 0 : page_mapcount(page);
pr_emerg("page:%px count:%d mapcount:%d mapping:%px index:%#lx",
page, page_ref_count(page), mapcount,
@@ -60,6 +73,7 @@ void __dump_page(struct page *page, cons
pr_emerg("flags: %#lx(%pGp)\n", page->flags, &page->flags);
+hex_only:
print_hex_dump(KERN_ALERT, "raw: ", DUMP_PREFIX_NONE, 32,
sizeof(unsigned long), page,
sizeof(struct page), false);
@@ -68,7 +82,7 @@ void __dump_page(struct page *page, cons
pr_alert("page dumped because: %s\n", reason);
#ifdef CONFIG_MEMCG
- if (page->mem_cgroup)
+ if (!page_poisoned && page->mem_cgroup)
pr_alert("page->mem_cgroup:%px\n", page->mem_cgroup);
#endif
}
_
Patches currently in -mm which might be from pasha.tatashin@xxxxxxxxxx are
mm-teach-dump_page-to-correctly-output-poisoned-struct-pages.patch
mm-skip-invalid-pages-block-at-a-time-in-zero_resv_unresv.patch
sparc64-ng4-memset-32-bits-overflow.patch
