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authorEric Biggers <ebiggers@google.com>2020-03-05 00:41:38 -0800
committerEric Biggers <ebiggers@google.com>2020-03-07 18:43:07 -0800
commit2b4eae95c7361e0a147b838715c8baa1380a428f (patch)
tree4c892e145402b8da6d2de8a5f8552dde1c91577f /fs/crypto
parent98d54f81e36ba3bf92172791eba5ca5bd813989b (diff)
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/crypto')
-rw-r--r--fs/crypto/keysetup.c9
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* immediately become outdated.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