diff options
author | Hugh Dickins <hugh@veritas.com> | 2009-01-06 14:39:32 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-06 15:59:03 -0800 |
commit | 878b63ac889df706d01048f2c110e322ad2f996d (patch) | |
tree | e0bd69b890fda939fc190675d977dd0fd75e0427 /firmware | |
parent | 2da02997e08d3efe8174c7a47696e6f7cbe69ba9 (diff) |
mm: gup persist for write permission
do_wp_page()'s VM_FAULT_WRITE return value tells __get_user_pages() that
COW has been done if necessary, though it may be leaving the pte without
write permission - for the odd case of forced writing to a readonly vma
for ptrace. At present GUP then retries the follow_page() without asking
for write permission, to escape an endless loop when forced.
But an application may be relying on GUP to guarantee a writable page
which won't be COWed again when written from userspace, whereas a race
here might leave a readonly pte in place? Change the VM_FAULT_WRITE
handling to ask follow_page() for write permission again, except in that
odd case of forced writing to a readonly vma.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Robin Holt <holt@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'firmware')
0 files changed, 0 insertions, 0 deletions