vfs: embed struct filename inside of names_cache allocation if possible (7950e385) · Commits · 戴 / test

fs/namei.c

+49 −20

Original line number	Diff line number	Diff line
		@@ -119,40 +119,69 @@
		*/
		void final_putname(struct filename *name)
		{
		if (name->separate) {
		__putname(name->name);
		kfree(name);
		} else {
		__putname(name);
		}
		}

		#define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))

		static struct filename *
		getname_flags(const char __user filename, int flags, int empty)
		{
		struct filename result, err;
		char *kname;
		int len;
		long max;
		char *kname;

		result = audit_reusename(filename);
		if (result)
		return result;

		/* FIXME: create dedicated slabcache? */
		result = kzalloc(sizeof(*result), GFP_KERNEL);
		result = __getname();
		if (unlikely(!result))
		return ERR_PTR(-ENOMEM);

		kname = __getname();
		if (unlikely(!kname)) {
		err = ERR_PTR(-ENOMEM);
		goto error_free_name;
		}

		/*
		* First, try to embed the struct filename inside the names_cache
		* allocation
		*/
		kname = (char )result + sizeof(result);
		result->name = kname;
		result->uptr = filename;
		len = strncpy_from_user(kname, filename, PATH_MAX);
		result->separate = false;
		max = EMBEDDED_NAME_MAX;

		recopy:
		len = strncpy_from_user(kname, filename, max);
		if (unlikely(len < 0)) {
		err = ERR_PTR(len);
		goto error;
		}

		/*
		* Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
		* separate struct filename so we can dedicate the entire
		* names_cache allocation for the pathname, and re-do the copy from
		* userland.
		*/
		if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
		kname = (char *)result;

		result = kzalloc(sizeof(*result), GFP_KERNEL);
		if (!result) {
		err = ERR_PTR(-ENOMEM);
		result = (struct filename *)kname;
		goto error;
		}
		result->name = kname;
		result->separate = true;
		max = PATH_MAX;
		goto recopy;
		}

		/* The empty path is special. */
		if (unlikely(!len)) {
		if (empty)
		@@ -163,15 +192,15 @@ getname_flags(const char __user filename, int flags, int empty)
		}

		err = ERR_PTR(-ENAMETOOLONG);
		if (likely(len < PATH_MAX)) {
		if (unlikely(len >= PATH_MAX))
		goto error;

		result->uptr = filename;
		audit_getname(result);
		return result;
		}

		error:
		__putname(kname);
		error_free_name:
		kfree(result);
		final_putname(result);
		return err;
		}

include/linux/fs.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -2201,6 +2201,7 @@ struct filename {
		const char name; / pointer to actual string */
		const __user char uptr; / original userland pointer */
		struct audit_names *aname;
		bool separate; /* should "name" be freed? */
		};

		extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,

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