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Filename Latest commit message Latest commit date
Nadav Amit d766826eee userfaultfd: prevent concurrent API initialization
[ Upstream commit 22e5fe2a2a279d9a6fcbdfb4dffe73821bef1c90 ]

userfaultfd assumes that the enabled features are set once and never
changed after UFFDIO_API ioctl succeeded.

However, currently, UFFDIO_API can be called concurrently from two
different threads, succeed on both threads and leave userfaultfd's
features in non-deterministic state.  Theoretically, other uffd operations
(ioctl's and page-faults) can be dispatched while adversely affected by
such changes of features.

Moreover, the writes to ctx->state and ctx->features are not ordered,
which can - theoretically, again - let userfaultfd_ioctl() think that
userfaultfd API completed, while the features are still not initialized.

To avoid races, it is arguably best to get rid of ctx->state.  Since there
are only 2 states, record the API initialization in ctx->features as the
uppermost bit and remove ctx->state.

Link: https://lkml.kernel.org/r/20210808020724.1022515-3-namit@vmware.com
Fixes: 9cd75c3cd4 ("userfaultfd: non-cooperative: add ability to report non-PF events from uffd descriptor")
Signed-off-by: Nadav Amit <namit@vmware.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-09-22 12:26:26 +02:00
arch MIPS: Malta: fix alignment of the devicetree buffer 2021-09-22 12:26:26 +02:00
block scsi: bsg: Remove support for SCSI_IOCTL_SEND_COMMAND 2021-09-22 12:26:23 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:47:29 +02:00
crypto crypto: shash - avoid comparing pointers to exported functions under CFI 2021-07-14 16:53:13 +02:00
Documentation docs: Fix infiniband uverbs minor number 2021-09-22 12:26:23 +02:00
drivers clk: at91: clk-generated: Limit the requested rate to our range 2021-09-22 12:26:25 +02:00
fs userfaultfd: prevent concurrent API initialization 2021-09-22 12:26:26 +02:00
include SUNRPC: Fix potential memory corruption 2021-09-22 12:26:24 +02:00
init kbuild: add CONFIG_LD_IS_LLD 2021-06-30 08:47:44 -04:00
ipc
kernel dma-debug: fix debugfs initialization order 2021-09-22 12:26:24 +02:00
lib lib/mpi: use kcalloc in mpi_resize 2021-09-15 09:47:29 +02:00
LICENSES
mm mm/page_alloc: speed up the iteration of max_order 2021-09-12 08:56:41 +02:00
net SUNRPC: Fix potential memory corruption 2021-09-22 12:26:24 +02:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-14 16:53:30 +02:00
scripts kbuild: Fix 'no symbols' warning when CONFIG_TRIM_UNUSD_KSYMS=y 2021-09-22 12:26:26 +02:00
security IMA: remove the dependency on CRYPTO_MD5 2021-09-15 09:47:41 +02:00
sound ASoC: wcd9335: Disable irq on slave ports in the remove function 2021-09-15 09:47:37 +02:00
tools tools/thermal/tmon: Add cross compiling support 2021-09-22 12:26:20 +02:00
usr
virt KVM: Do not leak memory for duplicate debugfs directories 2021-08-12 13:21:03 +02:00
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Makefile Linux 5.4.147 2021-09-16 12:56:14 +02:00
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.

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.