On Wed, Feb 24, 2016 at 02:35:18PM +0100, Dmitry Vyukov wrote:
> The warning is this one:
>
> static inline int should_follow_link(struct nameidata *nd, struct path *link,
> int follow,
> struct inode *inode, unsigned seq)
> {
> ....
> WARN_ON(!inode); // now, _that_ should not happen.
> return pick_link(nd, link, inode, seq);
> }
Let's try it with less chatty should_follow_link() and better set of
tripwires on the way to it:
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index c6d7d3d..86f81e3 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -323,6 +323,7 @@ static struct dentry *autofs4_mountpoint_changed(struct path *path)
struct dentry *new = d_lookup(parent, &dentry->d_name);
if (!new)
return NULL;
+ WARN_ON(d_is_negative(new));
ino = autofs4_dentry_ino(new);
ino->last_used = jiffies;
dput(path->dentry);
diff --git a/fs/namei.c b/fs/namei.c
index f624d13..071a4ba 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1209,6 +1209,7 @@ static int follow_managed(struct path *path, struct nameidata *nd)
/* Handle an automount point */
if (managed & DCACHE_NEED_AUTOMOUNT) {
ret = follow_automount(path, nd, &need_mntput);
+ WARN_ON(d_is_negative(path->dentry));
if (ret < 0)
break;
continue;
@@ -1582,8 +1583,10 @@ static int lookup_fast(struct nameidata *nd,
return -ENOENT;
path->mnt = mnt;
path->dentry = dentry;
- if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
+ if (likely(__follow_mount_rcu(nd, path, inode, seqp))) {
+ WARN_ON(!*inode);
return 0;
+ }
unlazy:
if (unlazy_walk(nd, dentry, seq))
return -ECHILD;
@@ -1613,8 +1616,10 @@ unlazy:
path->mnt = mnt;
path->dentry = dentry;
err = follow_managed(path, nd);
- if (likely(!err))
+ if (likely(!err)) {
*inode = d_backing_inode(path->dentry);
+ WARN_ON(!*inode);
+ }
return err;
need_lookup:
@@ -1712,6 +1717,12 @@ static inline int should_follow_link(struct nameidata *nd, struct path *link,
return 0;
if (!follow)
return 0;
+ /* make sure that d_is_symlink above matches inode */
+ if (nd->flags & LOOKUP_RCU) {
+ if (read_seqcount_retry(&link->dentry->d_seq, seq))
+ return -ECHILD;
+ }
+ WARN_ON(!inode); // now, _that_ should not happen.
return pick_link(nd, link, inode, seq);
}
@@ -1743,11 +1754,11 @@ static int walk_component(struct nameidata *nd, int flags)
if (err < 0)
return err;
- inode = d_backing_inode(path.dentry);
seq = 0; /* we are already out of RCU mode */
err = -ENOENT;
if (d_is_negative(path.dentry))
goto out_path_put;
+ inode = d_backing_inode(path.dentry);
}
if (flags & WALK_PUT)
@@ -3106,8 +3117,10 @@ static int do_last(struct nameidata *nd,
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
/* we _can_ be in RCU mode here */
error = lookup_fast(nd, &path, &inode, &seq);
- if (likely(!error))
+ if (likely(!error)) {
+ WARN_ON(!inode);
goto finish_lookup;
+ }
if (error < 0)
return error;
@@ -3192,12 +3205,13 @@ retry_lookup:
return error;
BUG_ON(nd->flags & LOOKUP_RCU);
- inode = d_backing_inode(path.dentry);
seq = 0; /* out of RCU mode, so the value doesn't matter */
if (unlikely(d_is_negative(path.dentry))) {
path_to_nameidata(&path, nd);
return -ENOENT;
}
+ inode = d_backing_inode(path.dentry);
+ WARN_ON(!inode);
finish_lookup:
if (nd->depth)
put_link(nd);
@@ -3206,11 +3220,6 @@ finish_lookup:
if (unlikely(error))
return error;
- if (unlikely(d_is_symlink(path.dentry)) && !(open_flag & O_PATH)) {
- path_to_nameidata(&path, nd);
- return -ELOOP;
- }
-
if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path.mnt) {
path_to_nameidata(&path, nd);
} else {
@@ -3229,6 +3238,10 @@ finish_open:
return error;
}
audit_inode(nd->name, nd->path.dentry, 0);
+ if (unlikely(d_is_symlink(nd->path.dentry)) && !(open_flag & O_PATH)) {
+ error = -ELOOP;
+ goto out;
+ }
error = -EISDIR;
if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
goto out;
@@ -3273,6 +3286,10 @@ opened:
goto exit_fput;
}
out:
+ if (unlikely(error > 0)) {
+ WARN_ON(1);
+ error = -EINVAL;
+ }
if (got_write)
mnt_drop_write(nd->path.mnt);
path_put(&save_parent);
--
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