From ea251c1d5c481cda1cf6b0c9e4965f04a6cf2ffc Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Wed, 24 Nov 2010 12:57:13 -0800 Subject: [PATCH] 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//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 Cc: Jun'ichi Nomura Acked-by: KAMEZAWA Hiroyuki Cc: Matt Mackall Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index da6b01d70f01..c126c83b9a45 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;