[PATCH v8 08/11] fs: make do_linkat() take struct filename

Dmitry Kadashev
2021-07-07T12:28:15Z

Pass in the struct filename pointers instead of the user string, for
uniformity with do_renameat2, do_unlinkat, do_mknodat, etc.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/io-uring/20210330071700.kpjoyp5zlni7uejm@wittgenstein/
Signed-off-by: Dmitry Kadashev <dkadashev@gmail.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
---
fs/namei.c | 45 +++++++++++++++++++++++++++++----------------
1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index ab7979f9daaa..c4e13bd8652f 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2450,7 +2450,7 @@ static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path
return err;
}

-int filename_lookup(int dfd, struct filename *name, unsigned flags,
+static int __filename_lookup(int dfd, struct filename *name, unsigned flags,
struct path *path, struct path *root)
{
int retval;
@@ -2472,6 +2472,14 @@ int filename_lookup(int dfd, struct filename *name, unsigned flags,
audit_inode(name, path->dentry,
flags & LOOKUP_MOUNTPOINT ? AUDIT_INODE_NOEVAL : 0);
restore_nameidata();
+ return retval;
+}
+
+int filename_lookup(int dfd, struct filename *name, unsigned flags,
+ struct path *path, struct path *root)
+{
+ int retval = __filename_lookup(dfd, name, flags, path, root);
+
putname(name);
return retval;
}
@@ -4351,8 +4359,8 @@ EXPORT_SYMBOL(vfs_link);
* with linux 2.0, and to avoid hard-linking to directories
* and other special files. --ADM
*/
-static int do_linkat(int olddfd, const char __user *oldname, int newdfd,
- const char __user *newname, int flags)
+static int do_linkat(int olddfd, struct filename *old, int newdfd,
+ struct filename *new, int flags)
{
struct user_namespace *mnt_userns;
struct dentry *new_dentry;
@@ -4361,31 +4369,32 @@ static int do_linkat(int olddfd, const char __user *oldname, int newdfd,
int how = 0;
int error;

- if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
- return -EINVAL;
+ if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) {
+ error = -EINVAL;
+ goto out_putnames;
+ }
/*
* To use null names we require CAP_DAC_READ_SEARCH
* This ensures that not everyone will be able to create
* handlink using the passed filedescriptor.
*/
- if (flags & AT_EMPTY_PATH) {
- if (!capable(CAP_DAC_READ_SEARCH))
- return -ENOENT;
- how = LOOKUP_EMPTY;
+ if (flags & AT_EMPTY_PATH && !capable(CAP_DAC_READ_SEARCH)) {
+ error = -ENOENT;
+ goto out_putnames;
}

if (flags & AT_SYMLINK_FOLLOW)
how |= LOOKUP_FOLLOW;
retry:
- error = user_path_at(olddfd, oldname, how, &old_path);
+ error = __filename_lookup(olddfd, old, how, &old_path, NULL);
if (error)
- return error;
+ goto out_putnames;

- new_dentry = user_path_create(newdfd, newname, &new_path,
+ new_dentry = __filename_create(newdfd, new, &new_path,
(how & LOOKUP_REVAL));
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
- goto out;
+ goto out_putpath;

error = -EXDEV;
if (old_path.mnt != new_path.mnt)
@@ -4413,8 +4422,11 @@ static int do_linkat(int olddfd, const char __user *oldname, int newdfd,
how |= LOOKUP_REVAL;
goto retry;
}
-out:
+out_putpath:
path_put(&old_path);
+out_putnames:
+ putname(old);
+ putname(new);

return error;
}
@@ -4422,12 +4434,13 @@ static int do_linkat(int olddfd, const char __user *oldname, int newdfd,
SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
int, newdfd, const char __user *, newname, int, flags)
{
- return do_linkat(olddfd, oldname, newdfd, newname, flags);
+ return do_linkat(olddfd, getname_uflags(oldname, flags),
+ newdfd, getname(newname), flags);
}

SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
{
- return do_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
+ return do_linkat(AT_FDCWD, getname(oldname), AT_FDCWD, getname(newname), 0);
}

/**
--
2.30.2