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| author | Eric Biggers <ebiggers@google.com> | 2020-03-05 11:41:38 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-03-18 09:17:53 +0300 |
| commit | ea1299be02e154cb306f557095961f244583822d (patch) | |
| tree | 2ea0b196f72cdf58d38b8ce7219874ce5c11b250 /fs | |
| parent | b7e54dd751fad5163efc63fd2de9be30eb417720 (diff) | |
| download | linux-ea1299be02e154cb306f557095961f244583822d.tar.xz | |
fscrypt: don't evict dirty inodes after removing key
commit 2b4eae95c7361e0a147b838715c8baa1380a428f upstream.
After FS_IOC_REMOVE_ENCRYPTION_KEY removes a key, it syncs the
filesystem and tries to get and put all inodes that were unlocked by the
key so that unused inodes get evicted via fscrypt_drop_inode().
Normally, the inodes are all clean due to the sync.
However, after the filesystem is sync'ed, userspace can modify and close
one of the files. (Userspace is *supposed* to close the files before
removing the key. But it doesn't always happen, and the kernel can't
assume it.) This causes the inode to be dirtied and have i_count == 0.
Then, fscrypt_drop_inode() failed to consider this case and indicated
that the inode can be dropped, causing the write to be lost.
On f2fs, other problems such as a filesystem freeze could occur due to
the inode being freed while still on f2fs's dirty inode list.
Fix this bug by making fscrypt_drop_inode() only drop clean inodes.
I've written an xfstest which detects this bug on ext4, f2fs, and ubifs.
Fixes: b1c0ec3599f4 ("fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl")
Cc: <stable@vger.kernel.org> # v5.4+
Link: https://lore.kernel.org/r/20200305084138.653498-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/crypto/keysetup.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index d71c2d6dd162..75898340eb46 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -579,6 +579,15 @@ int fscrypt_drop_inode(struct inode *inode) mk = ci->ci_master_key->payload.data[0]; /* + * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes + * protected by the key were cleaned by sync_filesystem(). But if + * userspace is still using the files, inodes can be dirtied between + * then and now. We mustn't lose any writes, so skip dirty inodes here. + */ + if (inode->i_state & I_DIRTY_ALL) + return 0; + + /* * Note: since we aren't holding ->mk_secret_sem, the result here can * immediately become outdated. But there's no correctness problem with * unnecessarily evicting. Nor is there a correctness problem with not |