The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From bfc2b7e8518999003a61f91c1deb5e88ed77b07d Mon Sep 17 00:00:00 2001
From: Eric Biggers ebiggers@google.com Date: Tue, 17 Nov 2020 23:56:07 -0800 Subject: [PATCH] f2fs: prevent creating duplicate encrypted filenames
As described in "fscrypt: add fscrypt_is_nokey_name()", it's possible to create a duplicate filename in an encrypted directory by creating a file concurrently with adding the directory's encryption key.
Fix this bug on f2fs by rejecting no-key dentries in f2fs_add_link().
Note that the weird check for the current task in f2fs_do_add_link() seems to make this bug difficult to reproduce on f2fs.
Fixes: 9ea97163c6da ("f2fs crypto: add filename encryption for f2fs_add_link") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201118075609.120337-4-ebiggers@kernel.org Signed-off-by: Eric Biggers ebiggers@google.com
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index cb700d797296..9a321c52face 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -3251,6 +3251,8 @@ bool f2fs_empty_dir(struct inode *dir);
static inline int f2fs_add_link(struct dentry *dentry, struct inode *inode) { + if (fscrypt_is_nokey_name(dentry)) + return -ENOKEY; return f2fs_do_add_link(d_inode(dentry->d_parent), &dentry->d_name, inode, inode->i_ino, inode->i_mode); }