Commit fc36def9 authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Linus Torvalds

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:

      VM_BUG_ON_PGFLAGS(PagePoisoned(page), page)
       dump_page() recursion loop.

Fixes: f165b378 ("mm: uninitialized struct page poisoning sanity checking")
Signed-off-by: default avatarPavel Tatashin <>
Acked-by: default avatarMichal Hocko <>
Cc: <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 5e4e290d
......@@ -43,12 +43,25 @@ const struct trace_print_flags vmaflag_names[] = {
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, const char *reason)
pr_emerg("flags: %#lx(%pGp)\n", page->flags, &page->flags);
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, const char *reason)
pr_alert("page dumped because: %s\n", reason);
if (page->mem_cgroup)
if (!page_poisoned && page->mem_cgroup)
pr_alert("page->mem_cgroup:%px\n", page->mem_cgroup);
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