From: Huacai Chen chenhc@lemote.com

[ Upstream commit c61c7def1fa0a722610d89790e0255b74f3c07dd ]

Commit ea7e0480a4b6 ("MIPS: VDSO: Always map near top of user memory") set VDSO_RANDOMIZE_SIZE to 256MB for 64bit kernel. But take a look at arch/mips/mm/mmap.c we can see that MIN_GAP is 128MB, which means the mmap_base may be at (user_address_top - 128MB). This make the stack be surrounded by mmaped areas, then stack expanding fails and causes a segmentation fault. Therefore, VDSO_RANDOMIZE_SIZE should be less than MIN_GAP and this patch reduce it to 64MB.

Signed-off-by: Huacai Chen chenhc@lemote.com Signed-off-by: Paul Burton paul.burton@mips.com Fixes: ea7e0480a4b6 ("MIPS: VDSO: Always map near top of user memory") Patchwork: https://patchwork.linux-mips.org/patch/20910/ Cc: Ralf Baechle ralf@linux-mips.org Cc: James Hogan jhogan@kernel.org Cc: linux-mips@linux-mips.org Cc: Fuxin Zhang zhangfx@lemote.com Cc: Zhangjin Wu wuzhangjin@gmail.com Cc: Huacai Chen chenhuacai@gmail.com Cc: stable@vger.kernel.org # 4.19 --- arch/mips/include/asm/processor.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h index 49d6046ca1d0..c373eb605040 100644 --- a/arch/mips/include/asm/processor.h +++ b/arch/mips/include/asm/processor.h @@ -81,7 +81,7 @@ extern unsigned int vced_count, vcei_count;

#endif

-#define VDSO_RANDOMIZE_SIZE (TASK_IS_32BIT_ADDR ? SZ_1M : SZ_256M) +#define VDSO_RANDOMIZE_SIZE (TASK_IS_32BIT_ADDR ? SZ_1M : SZ_64M)

extern unsigned long mips_stack_top(void); #define STACK_TOP mips_stack_top()