aboutsummaryrefslogtreecommitdiffstats
path: root/fs
diff options
context:
space:
mode:
authorWengang Wang <wen.gang.wang@oracle.com>2019-06-13 15:56:01 -0700
committerPaul Gortmaker <paul.gortmaker@windriver.com>2019-09-16 12:21:10 -0400
commit230035b7cc337678ea025f8fe89044b0e6c74fcd (patch)
treeee344b8b54138a29436fb3c7bc088edadd57bcd2 /fs
parenta0b46b08a84611526c142ae5530723f8b8a2e0e1 (diff)
downloadlinux-yocto-230035b7cc337678ea025f8fe89044b0e6c74fcd.tar.gz
linux-yocto-230035b7cc337678ea025f8fe89044b0e6c74fcd.tar.bz2
linux-yocto-230035b7cc337678ea025f8fe89044b0e6c74fcd.zip
fs/ocfs2: fix race in ocfs2_dentry_attach_lock()
commit be99ca2716972a712cde46092c54dee5e6192bf8 upstream. 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> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/ocfs2/dcache.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/fs/ocfs2/dcache.c b/fs/ocfs2/dcache.c
index 290373024d9d..e8ace3b54e9c 100644
--- a/fs/ocfs2/dcache.c
+++ b/fs/ocfs2/dcache.c
@@ -310,6 +310,18 @@ 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);