On Thu, 13 Feb 2014 12:48:29 -0800 Mark Fasheh <[email protected]> wrote:
> On Thu, Feb 13, 2014 at 01:18:46PM +0800, Joseph Qi wrote:
> > On 2014/2/13 7:29, Mark Fasheh wrote:
> > >> @@ -1097,6 +1174,22 @@ static int ocfs2_rename(struct inode *ol
> > >> goto bail;
> > >> }
> > >> rename_lock = 1;
> > >> +
> > >> + /* here we cannot guarantee the inodes haven't just been
> > >> + * changed, so check if they are nested again */
> > >> + status = ocfs2_check_if_ancestor(osb, new_dir->i_ino,
> > >> + old_inode->i_ino);
> > >> + if (status < 0) {
> > >> + mlog_errno(status);
> > >> + goto bail;
> > >> + } else if (status == 1) {
> > >> + status = -EPERM;
> > >> + mlog(ML_ERROR, "src inode %llu should not be
> > >> ancestor "
> > >> + "of new dir inode %llu\n",
> > >> + (unsigned long long)old_inode->i_ino,
> > >> + (unsigned long long)new_dir->i_ino);
> > >
> > > Is it possible for the user to trigger this mlog(ML_ERROR, "....") print
> > > at
> > > will? If so we need to make it a debug print otherwise we risk blowing up
> > > systemlog when someone abuses rename().
> > > --Mark
> > >
> > > --
> > > Mark Fasheh
> > >
> > >
> > The nested condition can be constructed but it is rare, isn't it?
> > And only one system log for one rename, so we log it as error message.
>
> It's not the rarity of it happening "naturally" that I'm worried about. If
> arguments to rename() can be constructed such that they trigger the print
> then a misbehaving user or program can flood the system log with repeating
> messages. We don't want to leave holes like that exposed - I can speak from
> experience that it results in angry system admins :)
We're still awaiting a resolution here...
From: Yiwen Jiang <[email protected]>
Subject: ocfs2: fix a tiny race when running dirop_fileop_racer
When running dirop_fileop_racer we found a dead lock case.
2 nodes, say Node A and Node B, mount the same ocfs2 volume. Create
/race/16/1 in the filesystem, and let the inode number of dir 16 is less
than the inode number of dir race.
Node A Node B
mv /race/16/1 /race/
right after Node A has got the
EX mode of /race/16/, and tries to
get EX mode of /race
ls /race/16/
In this case, Node A has got the EX mode of /race/16/, and wants to get EX
mode of /race/. Node B has got the PR mode of /race/, and wants to get
the PR mode of /race/16/. Since EX and PR are mutually exclusive, dead
lock happens.
This patch fixes this case by locking in ancestor order before trying
inode number order.
Signed-off-by: Yiwen Jiang <[email protected]>
Signed-off-by: Joseph Qi <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Mark Fasheh <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
fs/ocfs2/namei.c | 97 ++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 95 insertions(+), 2 deletions(-)
diff -puN
fs/ocfs2/namei.c~ocfs2-fix-a-tiny-race-when-running-dirop_fileop_racer
fs/ocfs2/namei.c
--- a/fs/ocfs2/namei.c~ocfs2-fix-a-tiny-race-when-running-dirop_fileop_racer
+++ a/fs/ocfs2/namei.c
@@ -995,6 +995,65 @@ leave:
return status;
}
+static int ocfs2_check_if_ancestor(struct ocfs2_super *osb,
+ u64 src_inode_no, u64 dest_inode_no)
+{
+ int ret = 0, i = 0;
+ u64 parent_inode_no = 0;
+ u64 child_inode_no = src_inode_no;
+ struct inode *child_inode;
+
+#define MAX_LOOKUP_TIMES 32
+ while (1) {
+ child_inode = ocfs2_iget(osb, child_inode_no, 0, 0);
+ if (IS_ERR(child_inode)) {
+ ret = PTR_ERR(child_inode);
+ break;
+ }
+
+ ret = ocfs2_inode_lock(child_inode, NULL, 0);
+ if (ret < 0) {
+ iput(child_inode);
+ if (ret != -ENOENT)
+ mlog_errno(ret);
+ break;
+ }
+
+ ret = ocfs2_lookup_ino_from_name(child_inode, "..", 2,
+ &parent_inode_no);
+ ocfs2_inode_unlock(child_inode, 0);
+ iput(child_inode);
+ if (ret < 0) {
+ ret = -ENOENT;
+ break;
+ }
+
+ if (parent_inode_no == dest_inode_no) {
+ ret = 1;
+ break;
+ }
+
+ if (parent_inode_no == osb->root_inode->i_ino) {
+ ret = 0;
+ break;
+ }
+
+ child_inode_no = parent_inode_no;
+
+ if (++i >= MAX_LOOKUP_TIMES) {
+ mlog(ML_NOTICE, "max lookup times reached, filesystem "
+ "may have nested directories, "
+ "src inode: %llu, dest inode: %llu.\n",
+ (unsigned long long)src_inode_no,
+ (unsigned long long)dest_inode_no);
+ ret = 0;
+ break;
+ }
+ }
+
+ return ret;
+}
+
/*
* The only place this should be used is rename!
* if they have the same id, then the 1st one is the only one locked.
@@ -1006,6 +1065,7 @@ static int ocfs2_double_lock(struct ocfs
struct inode *inode2)
{
int status;
+ int inode1_is_ancestor, inode2_is_ancestor;
struct ocfs2_inode_info *oi1 = OCFS2_I(inode1);
struct ocfs2_inode_info *oi2 = OCFS2_I(inode2);
struct buffer_head **tmpbh;
@@ -1019,9 +1079,26 @@ static int ocfs2_double_lock(struct ocfs
if (*bh2)
*bh2 = NULL;
- /* we always want to lock the one with the lower lockid first. */
+ /* we always want to lock the one with the lower lockid first.
+ * and if they are nested, we lock ancestor first */
if (oi1->ip_blkno != oi2->ip_blkno) {
- if (oi1->ip_blkno < oi2->ip_blkno) {
+ inode1_is_ancestor = ocfs2_check_if_ancestor(osb, oi2->ip_blkno,
+ oi1->ip_blkno);
+ if (inode1_is_ancestor < 0) {
+ status = inode1_is_ancestor;
+ goto bail;
+ }
+
+ inode2_is_ancestor = ocfs2_check_if_ancestor(osb, oi1->ip_blkno,
+ oi2->ip_blkno);
+ if (inode2_is_ancestor < 0) {
+ status = inode2_is_ancestor;
+ goto bail;
+ }
+
+ if ((inode1_is_ancestor == 1) ||
+ (oi1->ip_blkno < oi2->ip_blkno &&
+ inode2_is_ancestor == 0)) {
/* switch id1 and id2 around */
tmpbh = bh2;
bh2 = bh1;
@@ -1138,6 +1215,22 @@ static int ocfs2_rename(struct inode *ol
goto bail;
}
rename_lock = 1;
+
+ /* here we cannot guarantee the inodes haven't just been
+ * changed, so check if they are nested again */
+ status = ocfs2_check_if_ancestor(osb, new_dir->i_ino,
+ old_inode->i_ino);
+ if (status < 0) {
+ mlog_errno(status);
+ goto bail;
+ } else if (status == 1) {
+ status = -EPERM;
+ mlog(ML_ERROR, "src inode %llu should not be ancestor "
+ "of new dir inode %llu\n",
+ (unsigned long long)old_inode->i_ino,
+ (unsigned long long)new_dir->i_ino);
+ goto bail;
+ }
}
/* if old and new are the same, this'll just do one lock. */
_
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