[PATCH 5.17 0654/1126] MIPS: pgalloc: fix memory leak caused by pgd_free()

Greg Kroah-Hartman
2022-04-05T08:23:56Z

From: Yaliang Wang <Yaliang.Wang@windriver.com>

[ Upstream commit 2bc5bab9a763d520937e4f3fe8df51c6a1eceb97 ]

pgd page is freed by generic implementation pgd_free() since commit
f9cb654cb550 ("asm-generic: pgalloc: provide generic pgd_free()"),
however, there are scenarios that the system uses more than one page as
the pgd table, in such cases the generic implementation pgd_free() won't
be applicable anymore. For example, when PAGE_SIZE_4KB is enabled and
MIPS_VA_BITS_48 is not enabled in a 64bit system, the macro "PGD_ORDER"
will be set as "1", which will cause allocating two pages as the pgd
table. Well, at the same time, the generic implementation pgd_free()
just free one pgd page, which will result in the memory leak.

The memory leak can be easily detected by executing shell command:
"while true; do ls > /dev/null; grep MemFree /proc/meminfo; done"

Fixes: f9cb654cb550 ("asm-generic: pgalloc: provide generic pgd_free()")
Signed-off-by: Yaliang Wang <Yaliang.Wang@windriver.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/mips/include/asm/pgalloc.h | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/arch/mips/include/asm/pgalloc.h b/arch/mips/include/asm/pgalloc.h
index c7925d0e9874..867e9c3db76e 100644
--- a/arch/mips/include/asm/pgalloc.h
+++ b/arch/mips/include/asm/pgalloc.h
@@ -15,6 +15,7 @@

#define __HAVE_ARCH_PMD_ALLOC_ONE
#define __HAVE_ARCH_PUD_ALLOC_ONE
+#define __HAVE_ARCH_PGD_FREE
#include <asm-generic/pgalloc.h>

static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd,
@@ -48,6 +49,11 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
extern void pgd_init(unsigned long page);
extern pgd_t *pgd_alloc(struct mm_struct *mm);

+static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
+{
+ free_pages((unsigned long)pgd, PGD_ORDER);
+}
+
#define __pte_free_tlb(tlb,pte,address) \
do { \
pgtable_pte_page_dtor(pte); \
--
2.34.1