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Filename Latest commit message Latest commit date
Eric Biggers a0b3bc8553 fscrypt: lock mutex before checking for bounce page pool
fscrypt_initialize(), which allocates the global bounce page pool when
an encrypted file is first accessed, uses "double-checked locking" to
try to avoid locking fscrypt_init_mutex.  However, it doesn't use any
memory barriers, so it's theoretically possible for a thread to observe
a bounce page pool which has not been fully initialized.  This is a
classic bug with "double-checked locking".

While "only a theoretical issue" in the latest kernel, in pre-4.8
kernels the pointer that was checked was not even the last to be
initialized, so it was easily possible for a crash (NULL pointer
dereference) to happen.  This was changed only incidentally by the large
refactor to use fs/crypto/.

Solve both problems in a trivial way that can easily be backported: just
always take the mutex.  It's theoretically less efficient, but it
shouldn't be noticeable in practice as the mutex is only acquired very
briefly once per encrypted file.

Later I'd like to make this use a helper macro like DO_ONCE().  However,
DO_ONCE() runs in atomic context, so we'd need to add a new macro that
allows blocking.

Cc: stable@vger.kernel.org # v4.1+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2017-10-31 13:49:25 -04:00
arch Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-10-01 13:55:32 -07:00
block block: fix a crash caused by wrong API 2017-09-25 08:56:05 -06:00
certs
crypto crypto: af_alg - update correct dst SGL entry 2017-09-20 17:42:42 +08:00
Documentation fscrypt: add a documentation file for filesystem-level encryption 2017-10-31 13:49:24 -04:00
drivers Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-10-01 13:55:32 -07:00
firmware
fs fscrypt: lock mutex before checking for bounce page pool 2017-10-31 13:49:25 -04:00
include fscrypt: new helper function - fscrypt_prepare_setattr() 2017-10-18 19:52:39 -04:00
init
ipc fix a typo in put_compat_shm_info() 2017-09-25 20:41:46 -04:00
kernel Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-10-01 12:34:42 -07:00
lib Merge branch 'parisc-4.14-2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux 2017-09-23 06:14:06 -10:00
mm fs: Fix page cache inconsistency when mixing buffered and AIO DIO 2017-09-25 08:56:05 -06:00
net Revert "Bluetooth: Add option for disabling legacy ioctl interfaces" 2017-09-28 13:20:32 -07:00
samples
scripts objtool: Skip unreachable warnings for GCC 4.4 and older 2017-09-28 07:23:02 +02:00
security Merge commit 'keys-fixes-20170927' into fixes-v4.14-rc3 2017-09-28 09:11:28 +10:00
sound
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-10-01 12:06:31 -07:00
usr
virt Revert "KVM: Don't accept obviously wrong gsi values via KVM_IRQFD" 2017-09-19 08:37:17 +02:00
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MAINTAINERS fscrypt: add a documentation file for filesystem-level encryption 2017-10-31 13:49:24 -04:00
Makefile Linux 4.14-rc3 2017-10-01 14:54:54 -07:00
README

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

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.