mm: teach dump_page() to correctly output poisoned struct pages (fc36def9) · Commits · 戴 / test

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@oracle.com Fixes: ("mm: uninitialized struct page poisoning sanity checking") Signed-off-by:

Pavel Tatashin <pasha.tatashin@oracle.com> Acked-by:

Michal Hocko <mhocko@suse.com> Cc: <stable@vger.kernel.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/debug.c

+16 −2

Original line number	Diff line number	Diff line
		@@ -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);

		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, const char reason)
		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
		}

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