Commit 7844c014 authored by Oscar Salvador's avatar Oscar Salvador Committed by Andrew Morton
Browse files

mm,page_owner: fix recursion 

Prior to 217b2119 ("mm,page_owner: implement the tracking of the
stacks count") the only place where page_owner could potentially go into
recursion due to its need of allocating more memory was in save_stack(),
which ends up calling into stackdepot code with the possibility of
allocating memory.

We made sure to guard against that by signaling that the current task was
already in page_owner code, so in case a recursion attempt was made, we
could catch that and return dummy_handle.

After above commit, a new place in page_owner code was introduced where we
could allocate memory, meaning we could go into recursion would we take
that path.

Make sure to signal that we are in page_owner in that codepath as well. 
Move the guard code into two helpers {un}set_current_in_page_owner() and
use them prior to calling in the two functions that might allocate memory.

Link: https://lkml.kernel.org/r/20240315222610.6870-1-osalvador@suse.de


Signed-off-by: default avatarOscar Salvador <osalvador@suse.de>
Fixes: 217b2119 ("mm,page_owner: implement the tracking of the stacks count")
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
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: Oscar Salvador <osalvador@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 32900324

mm/page_owner.c

+23 −10
Original line number Diff line number Diff line
@@ -54,6 +54,22 @@ static depot_stack_handle_t early_handle; 


static void init_early_allocated_pages(void);



static inline void set_current_in_page_owner(void)

{

	/*

	 * Avoid recursion.

	 *

	 * We might need to allocate more memory from page_owner code, so make

	 * sure to signal it in order to avoid recursion.

	 */

	current->in_page_owner = 1;

}



static inline void unset_current_in_page_owner(void)

{

	current->in_page_owner = 0;

}



static int __init early_page_owner_param(char *buf)

{

	int ret = kstrtobool(buf, &page_owner_enabled);
@@ -133,23 +149,16 @@ static noinline depot_stack_handle_t save_stack(gfp_t flags) 
	depot_stack_handle_t handle;

	unsigned int nr_entries;



	/*

	 * Avoid recursion.

	 *

	 * Sometimes page metadata allocation tracking requires more

	 * memory to be allocated:

	 * - when new stack trace is saved to stack depot

	 */

	if (current->in_page_owner)

		return dummy_handle;

	current->in_page_owner = 1;



	set_current_in_page_owner();

	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);

	handle = stack_depot_save(entries, nr_entries, flags);

	if (!handle)

		handle = failure_handle;

	unset_current_in_page_owner();



	current->in_page_owner = 0;

	return handle;

}
@@ -164,9 +173,13 @@ static void add_stack_record_to_list(struct stack_record *stack_record, 
	gfp_mask &= (GFP_ATOMIC | GFP_KERNEL);

	gfp_mask |= __GFP_NOWARN;



	set_current_in_page_owner();

	stack = kmalloc(sizeof(*stack), gfp_mask);

	if (!stack)

	if (!stack) {

		unset_current_in_page_owner();

		return;

	}

	unset_current_in_page_owner();



	stack->stack_record = stack_record;

	stack->next = NULL;