diff options
authorNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>2010-11-24 12:57:13 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-11-25 06:50:46 +0900
commitea251c1d5c481cda1cf6b0c9e4965f04a6cf2ffc (patch)
parent5f0af70a25593a9d53b87bc8d31902fb7cc63e40 (diff)
pagemap: set pagemap walk limit to PMD boundary
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: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Matt Mackall <mpm@selenic.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index da6b01d70f0..c126c83b9a4 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.
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;