FAILED: patch "[PATCH] um: mm: check more comprehensively for stub changes" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Mar 1, 2021

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Stable branch User-mode Linux (UML)

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2021-03-01 13:38 UTC #0 lore raw

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 47da29763ec9a153b9b685bff9db659e4e09e494 Mon Sep 17 00:00:00 2001
From: Johannes Berg <[email protected]>
Date: Wed, 13 Jan 2021 22:08:02 +0100
Subject: [PATCH] um: mm: check more comprehensively for stub changes

If userspace tries to change the stub, we need to kill it, because otherwise it can escape the virtual machine. In a few cases the stub checks weren't good, e.g. if userspace just tries to

	mmap(0x100000 - 0x1000, 0x3000, ...)

it could succeed to get a new private/anonymous mapping replacing the stubs. Fix this by checking everywhere, and checking for _overlap_, not just direct changes.

Cc [email protected]

Fixes 3963333fe676 ("uml: cover stubs with a VMA")

Signed-off-by Johannes Berg <[email protected]>

Signed-off-by Richard Weinberger <[email protected]>

arch/um/kernel/tlb.c +11 -1

index 61776790cd67..89468da6bf88 100644
@@ -125,6 +125,9 @@ static int add_mmap(unsigned long virt, unsigned long phys, unsigned long len,
 	struct host_vm_op *last;
 	int fd = -1, ret = 0;
 
+	if (virt + len > STUB_START && virt < STUB_END)
+		return -EINVAL;
+
 	if (hvc->userspace)
 		fd = phys_mapping(phys, &offset);
 	else

@@ -162,7 +165,7 @@ static int add_munmap(unsigned long addr, unsigned long len,
 	struct host_vm_op *last;
 	int ret = 0;
 
-	if ((addr >= STUB_START) && (addr < STUB_END))
+	if (addr + len > STUB_START && addr < STUB_END)
 		return -EINVAL;
 
 	if (hvc->index != 0) {

@@ -192,6 +195,9 @@ static int add_mprotect(unsigned long addr, unsigned long len,
 	struct host_vm_op *last;
 	int ret = 0;
 
+	if (addr + len > STUB_START && addr < STUB_END)
+		return -EINVAL;
+
 	if (hvc->index != 0) {
 		last = &hvc->ops[hvc->index - 1];
 		if ((last->type == MPROTECT) &&

@@ -472,6 +478,10 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long address)
 	struct mm_id *mm_id;
 
 	address &= PAGE_MASK;
+
+	if (address >= STUB_START && address < STUB_END)
+		goto kill;
+
 	pgd = pgd_offset(mm, address);
 	if (!pgd_present(*pgd))
 		goto kill;