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commit 1b53cf9815bb4744958d41f3795d5d5a1d365e2d upstream.
Filesystem encryption ostensibly supported revoking a keyring key that
had been used to "unlock" encrypted files, causing those files to become
"locked" again. This was, however, buggy for several reasons, the most
severe of which was that when key revocation happened to be detected for
an inode, its fscrypt_info was immediately freed, even while other
threads could be using it for encryption or decryption concurrently.
This could be exploited to crash the kernel or worse.
This patch fixes the use-after-free by removing the code which detects
the keyring key having been revoked, invalidated, or expired. Instead,
an encrypted inode that is "unlocked" now simply remains unlocked until
it is evicted from memory. Note that this is no worse than the case for
block device-level encryption, e.g. dm-crypt, and it still remains
possible for a privileged user to evict unused pages, inodes, and
dentries by running 'sync; echo 3 > /proc/sys/vm/drop_caches', or by
simply unmounting the filesystem. In fact, one of those actions was
already needed anyway for key revocation to work even somewhat sanely.
This change is not expected to break any applications.
In the future I'd like to implement a real API for fscrypt key
revocation that interacts sanely with ongoing filesystem operations ---
waiting for existing operations to complete and blocking new operations,
and invalidating and sanitizing key material and plaintext from the VFS
caches. But this is a hard problem, and for now this bug must be fixed.
This bug affected almost all versions of ext4, f2fs, and ubifs
encryption, and it was potentially reachable in any kernel configured
with encryption support (CONFIG_EXT4_ENCRYPTION=y,
CONFIG_EXT4_FS_ENCRYPTION=y, CONFIG_F2FS_FS_ENCRYPTION=y, or
CONFIG_UBIFS_FS_ENCRYPTION=y). Note that older kernels did not use the
shared fs/crypto/ code, but due to the potential security implications
of this bug, it may still be worthwhile to backport this fix to them.
Fixes: b7236e21d55f ("ext4 crypto: reorganize how we store keys in the inode")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
Pull ext4 updates from Ted Ts'o:
"Lots of bug fixes and cleanups"
* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (40 commits)
ext4: remove unused variable
ext4: use journal inode to determine journal overhead
ext4: create function to read journal inode
ext4: unmap metadata when zeroing blocks
ext4: remove plugging from ext4_file_write_iter()
ext4: allow unlocked direct IO when pages are cached
ext4: require encryption feature for EXT4_IOC_SET_ENCRYPTION_POLICY
fscrypto: use standard macros to compute length of fname ciphertext
ext4: do not unnecessarily null-terminate encrypted symlink data
ext4: release bh in make_indexed_dir
ext4: Allow parallel DIO reads
ext4: allow DAX writeback for hole punch
jbd2: fix lockdep annotation in add_transaction_credits()
blockgroup_lock.h: simplify definition of NR_BG_LOCKS
blockgroup_lock.h: remove debris from bgl_lock_ptr() conversion
fscrypto: make filename crypto functions return 0 on success
fscrypto: rename completion callbacks to reflect usage
fscrypto: remove unnecessary includes
fscrypto: improved validation when loading inode encryption metadata
ext4: fix memory leak when symlink decryption fails
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- Validate fscrypt_context.format and fscrypt_context.flags. If
unrecognized values are set, then the kernel may not know how to
interpret the encrypted file, so it should fail the operation.
- Validate that AES_256_XTS is used for contents and that AES_256_CTS is
used for filenames. It was previously possible for the kernel to
accept these reversed, though it would have taken manual editing of
the block device. This was not intended.
- Fail cleanly rather than BUG()-ing if a file has an unexpected type.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Since setting an encryption policy requires writing metadata to the
filesystem, it should be guarded by mnt_want_write/mnt_drop_write.
Otherwise, a user could cause a write to a frozen or readonly
filesystem. This was handled correctly by f2fs but not by ext4. Make
fscrypt_process_policy() handle it rather than relying on the filesystem
to get it right.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Cc: stable@vger.kernel.org # 4.1+; check fs/{ext4,f2fs}
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>
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This patch allows fscrypto to handle a second key prefix given by filesystem.
The main reason is to provide backward compatibility, since previously f2fs
used "f2fs:" as a crypto prefix instead of "fscrypt:".
Later, ext4 should also provide key_prefix() to give "ext4:".
One concern decribed by Ted would be kinda double check overhead of prefixes.
In x86, for example, validate_user_key consumes 8 ms after boot-up, which turns
out derive_key_aes() consumed most of the time to load specific crypto module.
After such the cold miss, it shows almost zero latencies, which treats as a
negligible overhead.
Note that request_key() detects wrong prefix in prior to derive_key_aes() even.
Cc: Ted Tso <tytso@mit.edu>
Cc: stable@vger.kernel.org # v4.6
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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This patch fixes the issue introduced by the ext4 crypto fix in a same manner.
For F2FS, however, we flush the pending IOs and wait for a while to acquire free
memory.
Fixes: c9af28fdd4492 ("ext4 crypto: don't let data integrity writebacks fail with ENOMEM")
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs
Pull f2fs updates from Jaegeuk Kim:
"New Features:
- uplift filesystem encryption into fs/crypto/
- give sysfs entries to control memroy consumption
Enhancements:
- aio performance by preallocating blocks in ->write_iter
- use writepages lock for only WB_SYNC_ALL
- avoid redundant inline_data conversion
- enhance forground GC
- use wait_for_stable_page as possible
- speed up SEEK_DATA and fiiemap
Bug Fixes:
- corner case in terms of -ENOSPC for inline_data
- hung task caused by long latency in shrinker
- corruption between atomic write and f2fs_trace_pid
- avoid garbage lengths in dentries
- revoke atomicly written pages if an error occurs
In addition, there are various minor bug fixes and clean-ups"
* tag 'for-f2fs-4.6' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (81 commits)
f2fs: submit node page write bios when really required
f2fs: add missing argument to f2fs_setxattr stub
f2fs: fix to avoid unneeded unlock_new_inode
f2fs: clean up opened code with f2fs_update_dentry
f2fs: declare static functions
f2fs: use cryptoapi crc32 functions
f2fs: modify the readahead method in ra_node_page()
f2fs crypto: sync ext4_lookup and ext4_file_open
fs crypto: move per-file encryption from f2fs tree to fs/crypto
f2fs: mutex can't be used by down_write_nest_lock()
f2fs: recovery missing dot dentries in root directory
f2fs: fix to avoid deadlock when merging inline data
f2fs: introduce f2fs_flush_merged_bios for cleanup
f2fs: introduce f2fs_update_data_blkaddr for cleanup
f2fs crypto: fix incorrect positioning for GCing encrypted data page
f2fs: fix incorrect upper bound when iterating inode mapping tree
f2fs: avoid hungtask problem caused by losing wake_up
f2fs: trace old block address for CoWed page
f2fs: try to flush inode after merging inline data
f2fs: show more info about superblock recovery
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This patch adds the renamed functions moved from the f2fs crypto files.
1. definitions for per-file encryption used by ext4 and f2fs.
2. crypto.c for encrypt/decrypt functions
a. IO preparation:
- fscrypt_get_ctx / fscrypt_release_ctx
b. before IOs:
- fscrypt_encrypt_page
- fscrypt_decrypt_page
- fscrypt_zeroout_range
c. after IOs:
- fscrypt_decrypt_bio_pages
- fscrypt_pullback_bio_page
- fscrypt_restore_control_page
3. policy.c supporting context management.
a. For ioctls:
- fscrypt_process_policy
- fscrypt_get_policy
b. For context permission
- fscrypt_has_permitted_context
- fscrypt_inherit_context
4. keyinfo.c to handle permissions
- fscrypt_get_encryption_info
- fscrypt_free_encryption_info
5. fname.c to support filename encryption
a. general wrapper functions
- fscrypt_fname_disk_to_usr
- fscrypt_fname_usr_to_disk
- fscrypt_setup_filename
- fscrypt_free_filename
b. specific filename handling functions
- fscrypt_fname_alloc_buffer
- fscrypt_fname_free_buffer
6. Makefile and Kconfig
Cc: Al Viro <viro@ftp.linux.org.uk>
Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Ildar Muslukhov <ildarm@google.com>
Signed-off-by: Uday Savagaonkar <savagaon@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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