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Eric Biggers b699b0067c fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext 
commit b01531db6c upstream.

->lookup() in an encrypted directory begins as follows:

1. fscrypt_prepare_lookup():
    a. Try to load the directory's encryption key.
    b. If the key is unavailable, mark the dentry as a ciphertext name
       via d_flags.
2. fscrypt_setup_filename():
    a. Try to load the directory's encryption key.
    b. If the key is available, encrypt the name (treated as a plaintext
       name) to get the on-disk name.  Otherwise decode the name
       (treated as a ciphertext name) to get the on-disk name.

But if the key is concurrently added, it may be found at (2a) but not at
(1a).  In this case, the dentry will be wrongly marked as a ciphertext
name even though it was actually treated as plaintext.

This will cause the dentry to be wrongly invalidated on the next lookup,
potentially causing problems.  For example, if the racy ->lookup() was
part of sys_mount(), then the new mount will be detached when anything
tries to access it.  This is despite the mountpoint having a plaintext
path, which should remain valid now that the key was added.

Of course, this is only possible if there's a userspace race.  Still,
the additional kernel-side race is confusing and unexpected.

Close the kernel-side race by changing fscrypt_prepare_lookup() to also
set the on-disk filename (step 2b), consistent with the d_flags update.

Fixes: 28b4c26396 ("ext4 crypto: revalidate dentry after adding or removing the key")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-11-05 11:08:35 +01:00
arch x86/xen: disable Firmware First mode for correctable memory errors 2020-11-05 11:08:33 +01:00
block block: ratelimit handle_bad_sector() message 2020-10-30 10:38:26 +01:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: algif_skcipher - EBUSY on aio should be an error 2020-10-29 09:55:01 +01:00
Documentation fscrypt: return -EXDEV for incompatible rename or link into encrypted dir 2020-11-05 11:08:35 +01:00
drivers ata: sata_rcar: Fix DMA boundary mask 2020-11-05 11:08:35 +01:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext 2020-11-05 11:08:35 +01:00
include fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext 2020-11-05 11:08:35 +01:00
init printk: queue wake_up_klogd irq_work only if per-CPU areas are ready 2020-07-22 09:32:13 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:18:40 +02:00
kernel PM: hibernate: remove the bogus call to get_gendisk() in software_resume() 2020-10-30 10:38:28 +01:00
lib lib/crc32.c: fix trivial typo in preprocessor condition 2020-10-30 10:38:21 +01:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary 2020-10-29 09:55:15 +01:00
net tipc: fix memory leak caused by tipc_buf_append() 2020-11-05 11:08:33 +01:00
samples misc: vop: add round_up(x,4) for vring_size to avoid kernel panic 2020-10-30 10:38:29 +01:00
scripts scripts/setlocalversion: make git describe output more reliable 2020-11-05 11:08:31 +01:00
security evm: Check size of security.evm before using it 2020-11-05 11:08:34 +01:00
sound ALSA: seq: oss: Avoid mutex lock for a long-time ioctl 2020-10-29 09:55:11 +01:00
tools bpf: Fix comment for helper bpf_current_task_under_cgroup() 2020-11-05 11:08:34 +01:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch 2020-10-01 13:14:54 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-09-26 18:01:31 +02:00
Makefile Linux 4.19.154 2020-10-30 10:38:33 +01:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.