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| author | Wengang Wang <wen.gang.wang@oracle.com> | 2019-06-13 15:56:01 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-06-13 17:34:56 -1000 |
| commit | be99ca2716972a712cde46092c54dee5e6192bf8 (patch) | |
| tree | 56f54473a7b110df08a8cd33329962f7eb9be2cf | |
| parent | b17f18aff2876ceb3f1fde580c96cd489babf28e (diff) | |
| download | linux-be99ca2716972a712cde46092c54dee5e6192bf8.tar.gz linux-be99ca2716972a712cde46092c54dee5e6192bf8.tar.bz2 linux-be99ca2716972a712cde46092c54dee5e6192bf8.zip | |
fs/ocfs2: fix race in ocfs2_dentry_attach_lock()
ocfs2_dentry_attach_lock() can be executed in parallel threads against the
same dentry. Make that race safe. The race is like this:
thread A thread B
(A1) enter ocfs2_dentry_attach_lock,
seeing dentry->d_fsdata is NULL,
and no alias found by
ocfs2_find_local_alias, so kmalloc
a new ocfs2_dentry_lock structure
to local variable "dl", dl1
.....
(B1) enter ocfs2_dentry_attach_lock,
seeing dentry->d_fsdata is NULL,
and no alias found by
ocfs2_find_local_alias so kmalloc
a new ocfs2_dentry_lock structure
to local variable "dl", dl2.
......
(A2) set dentry->d_fsdata with dl1,
call ocfs2_dentry_lock() and increase
dl1->dl_lockres.l_ro_holders to 1 on
success.
......
(B2) set dentry->d_fsdata with dl2
call ocfs2_dentry_lock() and increase
dl2->dl_lockres.l_ro_holders to 1 on
success.
......
(A3) call ocfs2_dentry_unlock()
and decrease
dl2->dl_lockres.l_ro_holders to 0
on success.
....
(B3) call ocfs2_dentry_unlock(),
decreasing
dl2->dl_lockres.l_ro_holders, but
see it's zero now, panic
Link: http://lkml.kernel.org/r/20190529174636.22364-1-wen.gang.wang@oracle.com
Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Reported-by: Daniel Sobe <daniel.sobe@nxp.com>
Tested-by: Daniel Sobe <daniel.sobe@nxp.com>
Reviewed-by: Changwei Ge <gechangwei@live.cn>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/ocfs2/dcache.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/fs/ocfs2/dcache.c b/fs/ocfs2/dcache.c index 2d016937fdda..42a61eecdacd 100644 --- a/fs/ocfs2/dcache.c +++ b/fs/ocfs2/dcache.c @@ -296,6 +296,18 @@ int ocfs2_dentry_attach_lock(struct dentry *dentry, out_attach: spin_lock(&dentry_attach_lock); + if (unlikely(dentry->d_fsdata && !alias)) { + /* d_fsdata is set by a racing thread which is doing + * the same thing as this thread is doing. Leave the racing + * thread going ahead and we return here. + */ + spin_unlock(&dentry_attach_lock); + iput(dl->dl_inode); + ocfs2_lock_res_free(&dl->dl_lockres); + kfree(dl); + return 0; + } + dentry->d_fsdata = dl; dl->dl_count++; spin_unlock(&dentry_attach_lock); |