[PATCH 3.19 099/177] debugfs: leave freeing a symlink body until inode eviction

Greg Kroah-Hartman
2015-03-16T15:32:58Z

From: Al Viro <viro@zeniv.linux.org.uk>

commit 0db59e59299f0b67450c5db21f7f316c8fb04e84 upstream.

As it is, we have debugfs_remove() racing with symlink traversals.
Supply ->evict_inode() and do freeing there - inode will remain
pinned until we are done with the symlink body.

And rip the idiocy with checking if dentry is positive right after
we'd verified debugfs_positive(), which is a stronger check...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/debugfs/inode.c | 34 +++++++++++++++++-----------------
1 file changed, 17 insertions(+), 17 deletions(-)

--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -246,10 +246,19 @@ static int debugfs_show_options(struct s
return 0;
}

+static void debugfs_evict_inode(struct inode *inode)
+{
+ truncate_inode_pages_final(&inode->i_data);
+ clear_inode(inode);
+ if (S_ISLNK(inode->i_mode))
+ kfree(inode->i_private);
+}
+
static const struct super_operations debugfs_super_operations = {
.statfs = simple_statfs,
.remount_fs = debugfs_remount,
.show_options = debugfs_show_options,
+ .evict_inode = debugfs_evict_inode,
};

static int debug_fill_super(struct super_block *sb, void *data, int silent)
@@ -466,23 +475,14 @@ static int __debugfs_remove(struct dentr
int ret = 0;

if (debugfs_positive(dentry)) {
- if (dentry->d_inode) {
- dget(dentry);
- switch (dentry->d_inode->i_mode & S_IFMT) {
- case S_IFDIR:
- ret = simple_rmdir(parent->d_inode, dentry);
- break;
- case S_IFLNK:
- kfree(dentry->d_inode->i_private);
- /* fall through */
- default:
- simple_unlink(parent->d_inode, dentry);
- break;
- }
- if (!ret)
- d_delete(dentry);
- dput(dentry);
- }
+ dget(dentry);
+ if (S_ISDIR(dentry->d_inode->i_mode))
+ ret = simple_rmdir(parent->d_inode, dentry);
+ else
+ simple_unlink(parent->d_inode, dentry);
+ if (!ret)
+ d_delete(dentry);
+ dput(dentry);
}
return ret;
}