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Subject[PATCH 4.9 25/39] kaiser: kaiser_remove_mapping() move along the pgd
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hugh Dickins <hughd@google.com>


When removing the bogus comment from kaiser_remove_mapping(),
I really ought to have checked the extent of its bogosity: as
Neel points out, there is nothing to stop unmap_pud_range_nofree()
from continuing beyond the end of a pud (and starting in the wrong
position on the next).

Fix kaiser_remove_mapping() to constrain the extent and advance pgd
pointer correctly: use pgd_addr_end() macro as used throughout base
mm (but don't assume page-rounded start and size in this case).

But this bug was very unlikely to trigger in this backport: since
any buddy allocation is contained within a single pud extent, and
we are not using vmapped stacks (and are only mapping one page of
stack anyway): the only way to hit this bug here would be when
freeing a large modified ldt.

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/mm/kaiser.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -319,11 +319,13 @@ void kaiser_remove_mapping(unsigned long
extern void unmap_pud_range_nofree(pgd_t *pgd,
unsigned long start, unsigned long end);
unsigned long end = start + size;
- unsigned long addr;
+ unsigned long addr, next;
+ pgd_t *pgd;

- for (addr = start; addr < end; addr += PGDIR_SIZE) {
- pgd_t *pgd = native_get_shadow_pgd(pgd_offset_k(addr));
- unmap_pud_range_nofree(pgd, addr, end);
+ pgd = native_get_shadow_pgd(pgd_offset_k(start));
+ for (addr = start; addr < end; pgd++, addr = next) {
+ next = pgd_addr_end(addr, end);
+ unmap_pud_range_nofree(pgd, addr, next);
}
}


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