diff options
| author | hujianyang <hujianyang@huawei.com> | 2014-04-30 14:06:06 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-07-06 18:54:13 -0700 |
| commit | ac8df9ec7b4e25b87d5a71dfd9af4d8076d66bff (patch) | |
| tree | 3db074c5c49fb8e9d584a5f3a07eb86a4a73fcc1 /fs | |
| parent | 9a87f81f9393a91c01c1e3f8dc99458bf68d1d51 (diff) | |
UBIFS: fix an mmap and fsync race condition
commit 691a7c6f28ac90cccd0dbcf81348ea90b211bdd0 upstream.
There is a race condition in UBIFS:
Thread A (mmap) Thread B (fsync)
->__do_fault ->write_cache_pages
-> ubifs_vm_page_mkwrite
-> budget_space
-> lock_page
-> release/convert_page_budget
-> SetPagePrivate
-> TestSetPageDirty
-> unlock_page
-> lock_page
-> TestClearPageDirty
-> ubifs_writepage
-> do_writepage
-> release_budget
-> ClearPagePrivate
-> unlock_page
-> !(ret & VM_FAULT_LOCKED)
-> lock_page
-> set_page_dirty
-> ubifs_set_page_dirty
-> TestSetPageDirty (set page dirty without budgeting)
-> unlock_page
This leads to situation where we have a diry page but no budget allocated for
this page, so further write-back may fail with -ENOSPC.
In this fix we return from page_mkwrite without performing unlock_page. We
return VM_FAULT_LOCKED instead. After doing this, the race above will not
happen.
Signed-off-by: hujianyang <hujianyang@huawei.com>
Tested-by: Laurence Withers <lwithers@guralp.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/ubifs/file.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c index 14374530784c..881324c08430 100644 --- a/fs/ubifs/file.c +++ b/fs/ubifs/file.c @@ -1524,8 +1524,7 @@ static int ubifs_vm_page_mkwrite(struct vm_area_struct *vma, } wait_for_stable_page(page); - unlock_page(page); - return 0; + return VM_FAULT_LOCKED; out_unlock: unlock_page(page); |