Add arch_prctl getters/setters for size of virtual address space of task. This adds ability to change task's virtual address space limit. I need this for correctly restore virtual address space limits in CRIU. Currently, on x86 there are three task sizes: 3GB for some old 32 bit java apps, 4Gb for ordinary 32-bit compatible apps and 47-bits for native x86_64 processes. 32-bit applications are restored by CRIU with the help of 64-bit clone()-d child, and on restore we need to place correct address space limitations back - otherwise 32-bit restored application may mmap() address over 4Gb space and as this address will not fit into 4-byte pointer, it will silently reuse/corrupt the pointer that has the same lower 4-bytes.
Signed-off-by: Dmitry Safonov <[email protected]> --- arch/x86/include/uapi/asm/prctl.h | 3 +++ arch/x86/kernel/process_64.c | 13 +++++++++++++ 2 files changed, 16 insertions(+) diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h index 835aa51c7f6e..122a8ce5b051 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -6,6 +6,9 @@ #define ARCH_GET_FS 0x1003 #define ARCH_GET_GS 0x1004 +#define ARCH_SET_TASK_SIZE 0x1005 +#define ARCH_GET_TASK_SIZE 0x1006 + #define ARCH_MAP_VDSO_X32 0x2001 #define ARCH_MAP_VDSO_32 0x2002 #define ARCH_MAP_VDSO_64 0x2003 diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 8ce30d40bb33..ed6a792f7932 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -599,6 +599,19 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr) } #ifdef CONFIG_CHECKPOINT_RESTORE + case ARCH_SET_TASK_SIZE: + if (addr >= TASK_SIZE_MAX) + return -EINVAL; + if (find_vma(current->mm, addr) != 0) + return -ENOMEM; + current->mm->task_size = addr; + break; + + case ARCH_GET_TASK_SIZE: + ret = put_user(current->mm->task_size, + (unsigned long __user *)addr); + break; + # ifdef CONFIG_X86_X32_ABI case ARCH_MAP_VDSO_X32: return prctl_map_vdso(&vdso_image_x32, addr); -- 2.11.0
