linux-kernel - [PATCH 4.14 309/496] mm/page_owner: fix recursion bug after changing skip entries

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Date:   Mon, 28 May 2018 12:01:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Maninder Singh <maninder1.s@...sung.com>,
        Vaneet Narang <v.narang@...sung.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        Oscar Salvador <osalvador@...hadventures.net>,
        Ayush Mittal <ayush.m@...sung.com>,
        Prakash Gupta <guptap@...eaurora.org>,
        Vinayak Menon <vinmenon@...eaurora.org>,
        Vasyl Gomonovych <gomonovych@...il.com>,
        Amit Sahrawat <a.sahrawat@...sung.com>, pankaj.m@...sung.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.14 309/496] mm/page_owner: fix recursion bug after changing skip entries

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maninder Singh <maninder1.s@...sung.com>

[ Upstream commit 299815a4fba9f3c7a81434dba0072148f1690608 ]

This patch fixes commit 5f48f0bd4e36 ("mm, page_owner: skip unnecessary
stack_trace entries").

Because if we skip first two entries then logic of checking count value
as 2 for recursion is broken and code will go in one depth recursion.

so we need to check only one call of _RET_IP(__set_page_owner) while
checking for recursion.

Current Backtrace while checking for recursion:-

  (save_stack)             from (__set_page_owner)  // (But recursion returns true here)
  (__set_page_owner)       from (get_page_from_freelist)
  (get_page_from_freelist) from (__alloc_pages_nodemask)
  (__alloc_pages_nodemask) from (depot_save_stack)
  (depot_save_stack)       from (save_stack)       // recursion should return true here
  (save_stack)             from (__set_page_owner)
  (__set_page_owner)       from (get_page_from_freelist)
  (get_page_from_freelist) from (__alloc_pages_nodemask+)
  (__alloc_pages_nodemask) from (depot_save_stack)
  (depot_save_stack)       from (save_stack)
  (save_stack)             from (__set_page_owner)
  (__set_page_owner)       from (get_page_from_freelist)

Correct Backtrace with fix:

  (save_stack)             from (__set_page_owner) // recursion returned true here
  (__set_page_owner)       from (get_page_from_freelist)
  (get_page_from_freelist) from (__alloc_pages_nodemask+)
  (__alloc_pages_nodemask) from (depot_save_stack)
  (depot_save_stack)       from (save_stack)
  (save_stack)             from (__set_page_owner)
  (__set_page_owner)       from (get_page_from_freelist)

Link: http://lkml.kernel.org/r/1521607043-34670-1-git-send-email-maninder1.s@samsung.com
Fixes: 5f48f0bd4e36 ("mm, page_owner: skip unnecessary stack_trace entries")
Signed-off-by: Maninder Singh <maninder1.s@...sung.com>
Signed-off-by: Vaneet Narang <v.narang@...sung.com>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Oscar Salvador <osalvador@...hadventures.net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Ayush Mittal <ayush.m@...sung.com>
Cc: Prakash Gupta <guptap@...eaurora.org>
Cc: Vinayak Menon <vinmenon@...eaurora.org>
Cc: Vasyl Gomonovych <gomonovych@...il.com>
Cc: Amit Sahrawat <a.sahrawat@...sung.com>
Cc: <pankaj.m@...sung.com>
Cc: Vaneet Narang <v.narang@...sung.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 mm/page_owner.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -123,13 +123,13 @@ void __reset_page_owner(struct page *pag
 static inline bool check_recursive_alloc(struct stack_trace *trace,
 					unsigned long ip)
 {
-	int i, count;
+	int i;
 
 	if (!trace->nr_entries)
 		return false;
 
-	for (i = 0, count = 0; i < trace->nr_entries; i++) {
-		if (trace->entries[i] == ip && ++count == 2)
+	for (i = 0; i < trace->nr_entries; i++) {
+		if (trace->entries[i] == ip)
 			return true;
 	}