This is a note to let you know that I've just added the patch titled MIPS: pgalloc: fix memory leak caused by pgd_free() to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mips-pgalloc-fix-memory-leak-caused-by-pgd_free.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 152c1fc7ef6dc290e8a386c3a215744f808a0359 Author: Yaliang Wang <Yaliang.Wang@xxxxxxxxxxxxx> Date: Thu Mar 10 19:31:16 2022 +0800 MIPS: pgalloc: fix memory leak caused by pgd_free() [ 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@xxxxxxxxxxxxx> Signed-off-by: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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); \