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| author | Eric Biggers <ebiggers@google.com> | 2020-03-05 00:41:38 -0800 |
|---|---|---|
| committer | Eric Biggers <ebiggers@google.com> | 2020-03-07 18:43:07 -0800 |
| commit | 2b4eae95c7361e0a147b838715c8baa1380a428f (patch) | |
| tree | 4c892e145402b8da6d2de8a5f8552dde1c91577f /fs | |
| parent | 98d54f81e36ba3bf92172791eba5ca5bd813989b (diff) | |
| download | linux-2b4eae95c7361e0a147b838715c8baa1380a428f.tar.bz2 | |
fscrypt: don't evict dirty inodes after removing key
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>
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 65cb09fa6ead..08c9f216a54d 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -539,6 +539,15 @@ 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 |