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Commit 3955333d authored by Laura Abbott's avatar Laura Abbott Committed by Linus Torvalds
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proc/kcore: don't bounds check against address 0 

The existing kcore code checks for bad addresses against __va(0) with
the assumption that this is the lowest address on the system.  This may
not hold true on some systems (e.g.  arm64) and produce overflows and
crashes.  Switch to using other functions to validate the address range.

It's currently only seen on arm64 and it's not clear if anyone wants to
use that particular combination on a stable release.  So this is not
urgent for stable.

Link: http://lkml.kernel.org/r/20180501201143.15121-1-labbott@redhat.com


Signed-off-by: default avatarLaura Abbott <labbott@redhat.com>
Tested-by: default avatarDave Anderson <anderson@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>a
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7aaf7727

fs/proc/kcore.c

+16 −7
Original line number Diff line number Diff line
@@ -209,25 +209,34 @@ kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg) 
{

	struct list_head *head = (struct list_head *)arg;

	struct kcore_list *ent;

	struct page *p;



	if (!pfn_valid(pfn))

		return 1;



	p = pfn_to_page(pfn);

	if (!memmap_valid_within(pfn, p, page_zone(p)))

		return 1;



	ent = kmalloc(sizeof(*ent), GFP_KERNEL);

	if (!ent)

		return -ENOMEM;

	ent->addr = (unsigned long)__va((pfn << PAGE_SHIFT));

	ent->addr = (unsigned long)page_to_virt(p);

	ent->size = nr_pages << PAGE_SHIFT;



	/* Sanity check: Can happen in 32bit arch...maybe */

	if (ent->addr < (unsigned long) __va(0))

	if (!virt_addr_valid(ent->addr))

		goto free_out;



	/* cut not-mapped area. ....from ppc-32 code. */

	if (ULONG_MAX - ent->addr < ent->size)

		ent->size = ULONG_MAX - ent->addr;



	/* cut when vmalloc() area is higher than direct-map area */

	if (VMALLOC_START > (unsigned long)__va(0)) {

		if (ent->addr > VMALLOC_START)

			goto free_out;

	/*

	 * We've already checked virt_addr_valid so we know this address

	 * is a valid pointer, therefore we can check against it to determine

	 * if we need to trim

	 */

	if (VMALLOC_START > ent->addr) {

		if (VMALLOC_START - ent->addr < ent->size)

			ent->size = VMALLOC_START - ent->addr;

	}