path: root/mm/Kconfig.debug
diff options
authorVlastimil Babka <>2019-09-23 15:34:42 -0700
committerLinus Torvalds <>2019-09-24 15:54:08 -0700
commit8974558f49a6a41b4a74db672e13bca616eff6d8 (patch)
treec70e582172bac85d7d27676a23a5eac218bd3473 /mm/Kconfig.debug
parent37389167a281f3ccb6bc958c32b2e088c7269fe0 (diff)
mm, page_owner, debug_pagealloc: save and dump freeing stack trace
The debug_pagealloc functionality is useful to catch buggy page allocator users that cause e.g. use after free or double free. When page inconsistency is detected, debugging is often simpler by knowing the call stack of process that last allocated and freed the page. When page_owner is also enabled, we record the allocation stack trace, but not freeing. This patch therefore adds recording of freeing process stack trace to page owner info, if both page_owner and debug_pagealloc are configured and enabled. With only page_owner enabled, this info is not useful for the memory leak debugging use case. dump_page() is adjusted to print the info. An example result of calling __free_pages() twice may look like this (note the page last free stack trace): BUG: Bad page state in process bash pfn:13d8f8 page:ffffc31984f63e00 refcount:-1 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0x1affff800000000() raw: 01affff800000000 dead000000000100 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 ffffffffffffffff 0000000000000000 page dumped because: nonzero _refcount page_owner tracks the page as freed page last allocated via order 0, migratetype Unmovable, gfp_mask 0xcc0(GFP_KERNEL) prep_new_page+0x143/0x150 get_page_from_freelist+0x289/0x380 __alloc_pages_nodemask+0x13c/0x2d0 khugepaged+0x6e/0xc10 kthread+0xf9/0x130 ret_from_fork+0x3a/0x50 page last free stack trace: free_pcp_prepare+0x134/0x1e0 free_unref_page+0x18/0x90 khugepaged+0x7b/0xc10 kthread+0xf9/0x130 ret_from_fork+0x3a/0x50 Modules linked in: CPU: 3 PID: 271 Comm: bash Not tainted 5.3.0-rc4-2.g07a1a73-default+ #57 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 04/01/2014 Call Trace: dump_stack+0x85/0xc0 bad_page.cold+0xba/0xbf rmqueue_pcplist.isra.0+0x6c5/0x6d0 rmqueue+0x2d/0x810 get_page_from_freelist+0x191/0x380 __alloc_pages_nodemask+0x13c/0x2d0 __get_free_pages+0xd/0x30 __pud_alloc+0x2c/0x110 copy_page_range+0x4f9/0x630 dup_mmap+0x362/0x480 dup_mm+0x68/0x110 copy_process+0x19e1/0x1b40 _do_fork+0x73/0x310 __x64_sys_clone+0x75/0x80 do_syscall_64+0x6e/0x1e0 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f10af854a10 ... Link: Signed-off-by: Vlastimil Babka <> Cc: Kirill A. Shutemov <> Cc: Matthew Wilcox <> Cc: Mel Gorman <> Cc: Michal Hocko <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/Kconfig.debug')
1 files changed, 3 insertions, 1 deletions
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 82b6a20898bd..327b3ebf23bf 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -21,7 +21,9 @@ config DEBUG_PAGEALLOC
Also, the state of page tracking structures is checked more often as
pages are being allocated and freed, as unexpected state changes
often happen for same reasons as memory corruption (e.g. double free,
- use-after-free).
+ use-after-free). The error reports for these checks can be augmented
+ with stack traces of last allocation and freeing of the page, when
+ PAGE_OWNER is also selected and enabled on boot.
For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
fill the pages with poison patterns after free_pages() and verify