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Commit 736f24d5 authored by Cyrill Gorcunov's avatar Cyrill Gorcunov Committed by Linus Torvalds
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c/r: prctl: drop VMA flags test on PR_SET_MM_ stack data assignment 



In commit b7643757 ("procfs: mark thread stack correctly in
proc/<pid>/maps") the stack allocated via clone() is marked in
/proc/<pid>/maps as [stack:%d] thus it might be out of the former
mm->start_stack/end_stack values (and even has some custom VMA flags
set).

So to be able to restore mm->start_stack/end_stack drop vma flags test,
but still require the underlying VMA to exist.

As always note this feature is under CONFIG_CHECKPOINT_RESTORE and
requires CAP_SYS_RESOURCE to be granted.

Signed-off-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 300f786b

kernel/sys.c

+0 −14
Original line number Diff line number Diff line
@@ -1786,14 +1786,6 @@ SYSCALL_DEFINE1(umask, int, mask) 
}



#ifdef CONFIG_CHECKPOINT_RESTORE

static bool vma_flags_mismatch(struct vm_area_struct *vma,

			       unsigned long required,

			       unsigned long banned)

{

	return (vma->vm_flags & required) != required ||

		(vma->vm_flags & banned);

}



static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)

{

	struct vm_area_struct *vma;
@@ -1931,12 +1923,6 @@ static int prctl_set_mm(int opt, unsigned long addr, 
			error = -EFAULT;

			goto out;

		}

#ifdef CONFIG_STACK_GROWSUP

		if (vma_flags_mismatch(vma, VM_READ | VM_WRITE | VM_GROWSUP, 0))

#else

		if (vma_flags_mismatch(vma, VM_READ | VM_WRITE | VM_GROWSDOWN, 0))

#endif

			goto out;

		if (opt == PR_SET_MM_START_STACK)

			mm->start_stack = addr;

		else if (opt == PR_SET_MM_ARG_START)