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authorOscar Salvador <osalvador@suse.de>2024-03-06 15:32:16 +0300
committerAndrew Morton <akpm@linux-foundation.org>2024-03-07 00:04:19 +0300
commit84d6ac31c34f2a6e056f967e6105160b6e2891c4 (patch)
treeb5b9282853229b0eab8299c31fa8958138925112 /mm
parent82b1c07a0af603e3c47b906c8e991dc96f01688e (diff)
downloadlinux-84d6ac31c34f2a6e056f967e6105160b6e2891c4.tar.xz
mm,page_owner: check for null stack_record before bumping its refcount
Patch series "page_owner: Fixup and cleanup". This patchset consists of a fixup by an error that was reported by intel robot, where it seems to be that by the time page_owner gets initialized, stackdepot has already depleted its allocation space and returns 0-handles, turning that into null stack_records when trying to retrieve the stack_record. I was not able to reproduce that from the config because it booted fine for me, but when setting e.g: dummy_handle to 0 artificially, I could see the same error that was reported. The second patch is a cleanup that can also lead to a compilation warning. This patch (of 2): Although the retrieval of the stack_records for {dummy,failure}_handle happen when page_owner gets initialized, there seems to be some situations where stackdepot space has been already depleted by then, so we get 0-handles which make stack_records being NULL for those cases. Be careful to 1) only bump stack_records refcount and 2) only access stack_record fields if we actually have a non-null stack_record between hands. Link: https://lkml.kernel.org/r/20240306123217.29774-1-osalvador@suse.de Link: https://lkml.kernel.org/r/20240306123217.29774-2-osalvador@suse.de Fixes: 4bedfb314bdd ("mm,page_owner: implement the tracking of the stacks count") Signed-off-by: Oscar Salvador <osalvador@suse.de> Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202403051032.e2f865a-lkp@intel.com Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Marco Elver <elver@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/page_owner.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 033e349f6479..7163a1c44ccf 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -107,8 +107,10 @@ static __init void init_page_owner(void)
/* Initialize dummy and failure stacks and link them to stack_list */
dummy_stack.stack_record = __stack_depot_get_stack_record(dummy_handle);
failure_stack.stack_record = __stack_depot_get_stack_record(failure_handle);
- refcount_set(&dummy_stack.stack_record->count, 1);
- refcount_set(&failure_stack.stack_record->count, 1);
+ if (dummy_stack.stack_record)
+ refcount_set(&dummy_stack.stack_record->count, 1);
+ if (failure_stack.stack_record)
+ refcount_set(&failure_stack.stack_record->count, 1);
dummy_stack.next = &failure_stack;
stack_list = &dummy_stack;
}
@@ -856,6 +858,9 @@ static int stack_print(struct seq_file *m, void *v)
unsigned long nr_entries;
struct stack_record *stack_record = stack->stack_record;
+ if (!stack->stack_record)
+ return 0;
+
nr_entries = stack_record->size;
entries = stack_record->entries;
stack_count = refcount_read(&stack_record->count) - 1;