Commit 12ba780d authored Jun 07, 2018 by Amir Goldstein Committed by Linus Torvalds Jun 07, 2018

tmpfs: allow decoding a file handle of an unlinked file

tmpfs uses the helper d_find_alias() to find a dentry from a decoded
inode, but d_find_alias() skips unhashed dentries, so unlinked files
cannot be decoded from a file handle.

This can be reproduced using xfstests test program open_by_handle:

  $ open_by handle -c /tmp/testdir
  $ open_by_handle -dk /tmp/testdir
  open_by_handle(/tmp/testdir/file000000) returned 116 incorrectly on an unlinked open file!

To fix this, if d_find_alias() can't find a hashed alias, call
d_find_any_alias() to return an unhashed one.

Link: http://lkml.kernel.org/r/CAOQ4uxg+qSLP0KwdW+h1tcPqOCQd+_pGZVXiePQB1TXCMBMctQ@mail.gmail.com


Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: NeilBrown <neilb@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 88484826

mm/shmem.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -3209,6 +3209,15 @@ static int shmem_match(struct inode ino, void vfh)
		return ino->i_ino == inum && fh[0] == ino->i_generation;
		}

		/* Find any alias of inode, but prefer a hashed alias */
		static struct dentry shmem_find_alias(struct inode inode)
		{
		struct dentry *alias = d_find_alias(inode);

		return alias ?: d_find_any_alias(inode);
		}


		static struct dentry shmem_fh_to_dentry(struct super_block sb,
		struct fid *fid, int fh_len, int fh_type)
		{
		@@ -3225,7 +3234,7 @@ static struct dentry shmem_fh_to_dentry(struct super_block sb,
		inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
		shmem_match, fid->raw);
		if (inode) {
		dentry = d_find_alias(inode);
		dentry = shmem_find_alias(inode);
		iput(inode);
		}

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