linux-hardening - Re: [RFC PATCH v1 1/1] exec: seal system mappings

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Message-ID: <20241005200741.GA24353@redhat.com>
Date: Sat, 5 Oct 2024 22:08:05 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: jeffxu@...omium.org
Cc: akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com,
	torvalds@...ux-foundation.org, adhemerval.zanella@...aro.org,
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Subject: Re: [RFC PATCH v1 1/1] exec: seal system mappings

On 10/04, jeffxu@...omium.org wrote:
>
> It is important to note that the CHECKPOINT_RESTORE feature (CRIU) may
> alter the mapping of vdso, vvar, and sigpage during restore
> operations. Consequently, this feature cannot be universally enabled
> across all systems.

Can't review.

But as for uprobes, I'd prefer a simpler patch which doesn't need the new
CONFIG_ and/or kernel boot options, something like the patch below.

And I don't really like the fact that this patch changes the behaviour
of the "generic" _install_special_mapping() helper, but I won't argue.

Oleg.


--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -430,6 +430,8 @@ extern unsigned int kobjsize(const void *objp);
 #ifdef CONFIG_64BIT
 /* VM is sealed, in vm_flags */
 #define VM_SEALED	_BITUL(63)
+#else
+#define VM_SEALED	0
 #endif
 
 /* Bits set in the VMA until the stack is in its final location */
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 40ecab0971ff..388373c11593 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1510,7 +1510,7 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
 	}
 
 	vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
-				VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
+				VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO|VM_SEALED,
 				&xol_mapping);
 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);