Messages in this thread | | | Date | Mon, 22 Nov 2010 12:01:02 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [BUGFIX][PATCH] pagemap: set pagemap walk limit to PMD boundary |
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On Fri, 19 Nov 2010 18:07:45 +0900 Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:
> Currently one pagemap_read() call walks in PAGEMAP_WALK_SIZE bytes > (== 512 pages.) But there is a corner case where walk_pmd_range() > accidentally runs over a VMA associated with a hugetlbfs file. > > For example, when a process has mappings to VMAs as shown below: > > # cat /proc/<pid>/maps > ... > 3a58f6d000-3a58f72000 rw-p 00000000 00:00 0 > 7fbd51853000-7fbd51855000 rw-p 00000000 00:00 0 > 7fbd5186c000-7fbd5186e000 rw-p 00000000 00:00 0 > 7fbd51a00000-7fbd51c00000 rw-s 00000000 00:12 8614 /hugepages/test > > then pagemap_read() goes into walk_pmd_range() path and walks in the range > 0x7fbd51853000-0x7fbd51a53000, but the hugetlbfs VMA should be handled > by walk_hugetlb_range(). Otherwise PMD for the hugepage is considered bad > and cleared, which causes undesirable results. > > This patch fixes it by separating pagemap walk range into one PMD. > > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > Cc: Matt Mackall <mpm@selenic.com> > --- > fs/proc/task_mmu.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index da6b01d..c126c83 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -706,6 +706,7 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask, > * skip over unmapped regions. > */ > #define PAGEMAP_WALK_SIZE (PMD_SIZE) > +#define PAGEMAP_WALK_MASK (PMD_MASK) > static ssize_t pagemap_read(struct file *file, char __user *buf, > size_t count, loff_t *ppos) > { > @@ -776,7 +777,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, > unsigned long end; > > pm.pos = 0; > - end = start_vaddr + PAGEMAP_WALK_SIZE; > + end = (start_vaddr + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK; > /* overflow ? */ > if (end < start_vaddr || end > end_vaddr) > end = end_vaddr;
Ack.
But ALIGN() can't be used ?
Thanks, -Kame
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