There is no fundamental reason to use the int80_landing_pad symbol to adjust ip when moving the vdso. If ip falls within the vdso, and the vdso is moved, we should change the ip accordingly, regardless of mode or location within the vdso. This *currently* can only happen on 32 bits, but there isn't any reason not to do so generically.
Note that if this is ever possible from a vdso-internal call, then the user space stack will also needed to be adjusted (as well as the shadow stack, if enabled.) Fortunately this is not currently the case. At the moment, we don't even consider other threads when moving the vdso. The assumption is that it is only used by process freeze/thaw for migration, where this is not an issue. Signed-off-by: H. Peter Anvin (Intel) <[email protected]> --- arch/x86/entry/vdso/vma.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 8f98c2d7c7a9..e7fd7517370f 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -65,16 +65,12 @@ static vm_fault_t vdso_fault(const struct vm_special_mapping *sm, static void vdso_fix_landing(const struct vdso_image *image, struct vm_area_struct *new_vma) { - if (in_ia32_syscall() && image == &vdso32_image) { - struct pt_regs *regs = current_pt_regs(); - unsigned long vdso_land = image->sym_int80_landing_pad; - unsigned long old_land_addr = vdso_land + - (unsigned long)current->mm->context.vdso; - - /* Fixing userspace landing - look at do_fast_syscall_32 */ - if (regs->ip == old_land_addr) - regs->ip = new_vma->vm_start + vdso_land; - } + struct pt_regs *regs = current_pt_regs(); + unsigned long ipoffset = regs->ip - + (unsigned long)current->mm->context.vdso; + + if (ipoffset < image->size) + regs->ip = new_vma->vm_start + ipoffset; } static int vdso_mremap(const struct vm_special_mapping *sm, -- 2.51.1
