From 7844c01472119f55bd9a107a4578a6d26be04c46 Mon Sep 17 00:00:00 2001 From: Oscar Salvador Date: Fri, 15 Mar 2024 23:26:10 +0100 Subject: mm,page_owner: fix recursion Prior to 217b2119b9e2 ("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: Oscar Salvador Fixes: 217b2119b9e2 ("mm,page_owner: implement the tracking of the stacks count") Reviewed-by: Vlastimil Babka Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Marco Elver Cc: Michal Hocko Cc: Oscar Salvador Signed-off-by: Andrew Morton --- mm/page_owner.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/mm/page_owner.c b/mm/page_owner.c index e7139952ffd9d..d17d1351ec84a 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -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; -- cgit 1.2.3-korg