target/linux/generic/backport-5.10/350-v5.18-MIPS-pgalloc-fix-memory-leak-caused-by-pgd_free.patch

   1 From e852442da56f43795cb6255d90b9fd0c84b209bb Mon Sep 17 00:00:00 2001
   2 From: Yaliang Wang <Yaliang.Wang@windriver.com>
   3 Date: Thu, 10 Mar 2022 19:31:16 +0800
   4 Subject: [PATCH] MIPS: pgalloc: fix memory leak caused by pgd_free()
   5
   6 pgd page is freed by generic implementation pgd_free() since commit
   7 f9cb654cb550 ("asm-generic: pgalloc: provide generic pgd_free()"),
   8 however, there are scenarios that the system uses more than one page as
   9 the pgd table, in such cases the generic implementation pgd_free() won't
  10 be applicable anymore. For example, when PAGE_SIZE_4KB is enabled and
  11 MIPS_VA_BITS_48 is not enabled in a 64bit system, the macro "PGD_ORDER"
  12 will be set as "1", which will cause allocating two pages as the pgd
  13 table. Well, at the same time, the generic implementation pgd_free()
  14 just free one pgd page, which will result in the memory leak.
  15
  16 The memory leak can be easily detected by executing shell command:
  17 "while true; do ls > /dev/null; grep MemFree /proc/meminfo; done"
  18
  19 Fixes: f9cb654cb550 ("asm-generic: pgalloc: provide generic pgd_free()")
  20 Signed-off-by: Yaliang Wang <Yaliang.Wang@windriver.com>
  21 Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
  22 (cherry picked from commit 2bc5bab9a763d520937e4f3fe8df51c6a1eceb97)
  23 ---
  24  arch/mips/include/asm/pgalloc.h | 6 ++++++
  25  1 file changed, 6 insertions(+)
  26
  27 --- a/arch/mips/include/asm/pgalloc.h
  28 +++ b/arch/mips/include/asm/pgalloc.h
  29 @@ -15,6 +15,7 @@
  30
  31  #define __HAVE_ARCH_PMD_ALLOC_ONE
  32  #define __HAVE_ARCH_PUD_ALLOC_ONE
  33 +#define __HAVE_ARCH_PGD_FREE
  34  #include <asm-generic/pgalloc.h>
  35
  36  static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd,
  37 @@ -49,6 +50,11 @@ static inline void pud_populate(struct m
  38  extern void pgd_init(unsigned long page);
  39  extern pgd_t *pgd_alloc(struct mm_struct *mm);
  40
  41 +static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
  42 +{
  43 +       free_pages((unsigned long)pgd, PGD_ORDER);
  44 +}
  45 +
  46  #define __pte_free_tlb(tlb,pte,address)                        \
  47  do {                                                   \
  48         pgtable_pte_page_dtor(pte);                     \