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Subject[PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page()
Date
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@lca.pw>
---
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
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