[PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page()

[Qian Cai]

The linux-next commit "mm/sparsemem: Add helpers track active portions
of a section at boot" [1] causes a crash below when the first kmemleak
scan kthread kicks in. This is because kmemleak_scan() calls
pfn_to_online_page(() which calls pfn_valid_within() instead of
pfn_valid() on x86 due to CONFIG_HOLES_IN_ZONE=n.

The commit [1] did add an additional check of pfn_section_valid() in
pfn_valid(), but forgot to add it in the above code path.

page:ffffea0002748000 is uninitialized and poisoned
raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
------------[ cut here ]------------
kernel BUG at include/linux/mm.h:1084!
invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
CPU: 5 PID: 332 Comm: kmemleak Not tainted 5.2.0-rc4-next-20190612+ #6
Hardware name: Lenovo ThinkSystem SR530 -[7X07RCZ000]-/-[7X07RCZ000]-,
BIOS -[TEE113T-1.00]- 07/07/2017
RIP: 0010:kmemleak_scan+0x6df/0xad0
Call Trace:
 kmemleak_scan_thread+0x9f/0xc7
 kthread+0x1d2/0x1f0
 ret_from_fork+0x35/0x4

[1] https://patchwork.kernel.org/patch/10977957/

Signed-off-by: Qian Cai <cai@xxxxxx>
---
 include/linux/memory_hotplug.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 0b8a5e5ef2da..f02be86077e3 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -28,6 +28,7 @@
 	unsigned long ___nr = pfn_to_section_nr(___pfn);	   \
 								   \
 	if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr) && \
+	    pfn_section_valid(__nr_to_section(___nr), pfn) &&	   \
 	    pfn_valid_within(___pfn))				   \
 		___page = pfn_to_page(___pfn);			   \
 	___page;						   \
-- 
1.8.3.1