namei: don't mangle nd->seq in lookup_fast() (254cf582) · Commits · e / devices / android_kernel_fairphone_FP3

fs/namei.c

+23 −15

Original line number	Diff line number	Diff line
		@@ -1134,7 +1134,7 @@ static inline int managed_dentry_rcu(struct dentry *dentry)
		* we meet a managed dentry that would need blocking.
		*/
		static bool __follow_mount_rcu(struct nameidata nd, struct path path,
		struct inode **inode)
		struct inode *inode, unsigned seqp)
		{
		for (;;) {
		struct mount *mounted;
		@@ -1161,7 +1161,7 @@ static bool __follow_mount_rcu(struct nameidata nd, struct path path,
		path->mnt = &mounted->mnt;
		path->dentry = mounted->mnt.mnt_root;
		nd->flags \|= LOOKUP_JUMPED;
		nd->seq = read_seqcount_begin(&path->dentry->d_seq);
		*seqp = read_seqcount_begin(&path->dentry->d_seq);
		/*
		* Update the inode too. We don't need to re-check the
		* dentry sequence number here after this d_inode read,
		@@ -1397,7 +1397,8 @@ static struct dentry __lookup_hash(struct qstr name,
		* It _is_ time-critical.
		*/
		static int lookup_fast(struct nameidata *nd,
		struct path path, struct inode *inode)
		struct path path, struct inode *inode,
		unsigned *seqp)
		{
		struct vfsmount *mnt = nd->path.mnt;
		struct dentry dentry, parent = nd->path.dentry;
		@@ -1437,8 +1438,8 @@ static int lookup_fast(struct nameidata *nd,
		*/
		if (__read_seqcount_retry(&parent->d_seq, nd->seq))
		return -ECHILD;
		nd->seq = seq;

		*seqp = seq;
		if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
		status = d_revalidate(dentry, nd->flags);
		if (unlikely(status <= 0)) {
		@@ -1449,10 +1450,10 @@ static int lookup_fast(struct nameidata *nd,
		}
		path->mnt = mnt;
		path->dentry = dentry;
		if (likely(__follow_mount_rcu(nd, path, inode)))
		if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
		return 0;
		unlazy:
		if (unlazy_walk(nd, dentry, nd->seq))
		if (unlazy_walk(nd, dentry, seq))
		return -ECHILD;
		} else {
		dentry = __d_lookup(parent, &nd->last);
		@@ -1543,7 +1544,7 @@ static void terminate_walk(struct nameidata *nd)
		put_link(nd);
		}

		static int pick_link(struct nameidata nd, struct path link)
		static int pick_link(struct nameidata nd, struct path link, unsigned seq)
		{
		int error;
		struct saved *last;
		@@ -1553,7 +1554,7 @@ static int pick_link(struct nameidata nd, struct path link)
		}
		if (nd->flags & LOOKUP_RCU) {
		if (unlikely(nd->path.mnt != link->mnt \|\|
		unlazy_walk(nd, link->dentry, nd->seq))) {
		unlazy_walk(nd, link->dentry, seq))) {
		return -ECHILD;
		}
		}
		@@ -1577,13 +1578,14 @@ static int pick_link(struct nameidata nd, struct path link)
		* so we keep a cache of "no, this doesn't need follow_link"
		* for the common case.
		*/
		static inline int should_follow_link(struct nameidata nd, struct path link, int follow)
		static inline int should_follow_link(struct nameidata nd, struct path link,
		int follow, unsigned seq)
		{
		if (likely(!d_is_symlink(link->dentry)))
		return 0;
		if (!follow)
		return 0;
		return pick_link(nd, link);
		return pick_link(nd, link, seq);
		}

		enum {WALK_GET = 1, WALK_PUT = 2};
		@@ -1592,6 +1594,7 @@ static int walk_component(struct nameidata *nd, int flags)
		{
		struct path path;
		struct inode *inode;
		unsigned seq;
		int err;
		/*
		* "." and ".." are special - ".." especially so because it has
		@@ -1604,7 +1607,7 @@ static int walk_component(struct nameidata *nd, int flags)
		put_link(nd);
		return err;
		}
		err = lookup_fast(nd, &path, &inode);
		err = lookup_fast(nd, &path, &inode, &seq);
		if (unlikely(err)) {
		if (err < 0)
		return err;
		@@ -1614,6 +1617,7 @@ static int walk_component(struct nameidata *nd, int flags)
		return err;

		inode = path.dentry->d_inode;
		seq = 0; /* we are already out of RCU mode */
		err = -ENOENT;
		if (d_is_negative(path.dentry))
		goto out_path_put;
		@@ -1621,11 +1625,12 @@ static int walk_component(struct nameidata *nd, int flags)

		if (flags & WALK_PUT)
		put_link(nd);
		err = should_follow_link(nd, &path, flags & WALK_GET);
		err = should_follow_link(nd, &path, flags & WALK_GET, seq);
		if (unlikely(err))
		return err;
		path_to_nameidata(&path, nd);
		nd->inode = inode;
		nd->seq = seq;
		return 0;

		out_path_put:
		@@ -2342,7 +2347,7 @@ mountpoint_last(struct nameidata nd, struct path path)
		put_link(nd);
		path->dentry = dentry;
		path->mnt = nd->path.mnt;
		error = should_follow_link(nd, path, nd->flags & LOOKUP_FOLLOW);
		error = should_follow_link(nd, path, nd->flags & LOOKUP_FOLLOW, 0);
		if (unlikely(error))
		return error;
		mntget(path->mnt);
		@@ -2939,6 +2944,7 @@ static int do_last(struct nameidata *nd,
		bool will_truncate = (open_flag & O_TRUNC) != 0;
		bool got_write = false;
		int acc_mode = op->acc_mode;
		unsigned seq;
		struct inode *inode;
		struct path save_parent = { .dentry = NULL, .mnt = NULL };
		struct path path;
		@@ -2959,7 +2965,7 @@ static int do_last(struct nameidata *nd,
		if (nd->last.name[nd->last.len])
		nd->flags \|= LOOKUP_FOLLOW \| LOOKUP_DIRECTORY;
		/* we _can_ be in RCU mode here */
		error = lookup_fast(nd, &path, &inode);
		error = lookup_fast(nd, &path, &inode, &seq);
		if (likely(!error))
		goto finish_lookup;

		@@ -3047,6 +3053,7 @@ static int do_last(struct nameidata *nd,

		BUG_ON(nd->flags & LOOKUP_RCU);
		inode = path.dentry->d_inode;
		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;
		@@ -3054,7 +3061,7 @@ static int do_last(struct nameidata *nd,
		finish_lookup:
		if (nd->depth)
		put_link(nd);
		error = should_follow_link(nd, &path, nd->flags & LOOKUP_FOLLOW);
		error = should_follow_link(nd, &path, nd->flags & LOOKUP_FOLLOW, seq);
		if (unlikely(error))
		return error;

		@@ -3072,6 +3079,7 @@ static int do_last(struct nameidata *nd,

		}
		nd->inode = inode;
		nd->seq = seq;
		/* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
		finish_open:
		error = complete_walk(nd);