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proc/kcore: don't bounds check against address 0 

[ Upstream commit 3955333df9 ]

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: Laura Abbott <labbott@redhat.com>
Tested-by: Dave 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/10/head
Laura Abbott 2018-05-11 16:01:57 -07:00 committed by Greg Kroah-Hartman
parent 20e557fb26
commit 553495752c
1 changed files with 16 additions and 7 deletions
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23
fs/proc/kcore.c
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@ -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;
}