vfs: define struct filename and have getname() return it

getname() is intended to copy pathname strings from userspace into a
kernel buffer. The result is just a string in kernel space. It would
however be quite helpful to be able to attach some ancillary info to
the string.

For instance, we could attach some audit-related info to reduce the
amount of audit-related processing needed. When auditing is enabled,
we could also call getname() on the string more than once and not
need to recopy it from userspace.

This patchset converts the getname()/putname() interfaces to return
a struct instead of a string. For now, the struct just tracks the
string in kernel space and the original userland pointer for it.

Later, we'll add other information to the struct as it becomes
convenient.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 5 insertions, 6 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 14e254c768fc..90d2ed591de9 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1483,7 +1483,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
         struct file *swap_file, *victim;
         struct address_space *mapping;
         struct inode *inode;
-        char *pathname;
+        struct filename *pathname;
         int oom_score_adj;
         int i, type, prev;
         int err;
@@ -1498,8 +1498,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
         if (IS_ERR(pathname))
                 goto out;
 
-        victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
-        putname(pathname);
+        victim = filp_open(pathname->name, O_RDWR|O_LARGEFILE, 0);
         err = PTR_ERR(victim);
         if (IS_ERR(victim))
                 goto out;
@@ -1936,7 +1935,7 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
         struct swap_info_struct *p;
-        char *name;
+        struct filename *name;
         struct file *swap_file = NULL;
         struct address_space *mapping;
         int i;
@@ -1967,7 +1966,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
                 name = NULL;
                 goto bad_swap;
         }
-        swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
+        swap_file = filp_open(name->name, O_RDWR|O_LARGEFILE, 0);
         if (IS_ERR(swap_file)) {
                 error = PTR_ERR(swap_file);
                 swap_file = NULL;
@@ -2053,7 +2052,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 
         printk(KERN_INFO "Adding %uk swap on %s.  "
                         "Priority:%d extents:%d across:%lluk %s%s%s\n",
-                p->pages<<(PAGE_SHIFT-10), name, p->prio,
+                p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
                 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
                 (p->flags & SWP_DISCARDABLE) ? "D" : "",