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Mathieu Desnoyers 6fb761dbba rseq: Unregister rseq for clone CLONE_VM 
[ Upstream commit 463f550fb4 ]

It has been reported by Google that rseq is not behaving properly
with respect to clone when CLONE_VM is used without CLONE_THREAD.

It keeps the prior thread's rseq TLS registered when the TLS of the
thread has moved, so the kernel can corrupt the TLS of the parent.

The approach of clearing the per task-struct rseq registration
on clone with CLONE_THREAD flag is incomplete. It does not cover
the use-case of clone with CLONE_VM set, but without CLONE_THREAD.

Here is the rationale for unregistering rseq on clone with CLONE_VM
flag set:

1) CLONE_THREAD requires CLONE_SIGHAND, which requires CLONE_VM to be
   set. Therefore, just checking for CLONE_VM covers all CLONE_THREAD
   uses. There is no point in checking for both CLONE_THREAD and
   CLONE_VM,

2) There is the possibility of an unlikely scenario where CLONE_SETTLS
   is used without CLONE_VM. In order to be an issue, it would require
   that the rseq TLS is in a shared memory area.

   I do not plan on adding CLONE_SETTLS to the set of clone flags which
   unregister RSEQ, because it would require that we also unregister RSEQ
   on set_thread_area(2) and arch_prctl(2) ARCH_SET_FS for completeness.
   So rather than doing a partial solution, it appears better to let
   user-space explicitly perform rseq unregistration across clone if
   needed in scenarios where CLONE_VM is not set.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191211161713.4490-3-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-02-05 14:43:42 +00:00
arch ARM: dts: beagle-x15-common: Model 5V0 regulator 2020-02-05 14:43:41 +00:00
block block: fix 32 bit overflow in __blkdev_issue_discard() 2020-02-01 09:37:12 +00:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: pcrypt - Fix user-after-free on module unload 2020-02-05 14:43:32 +00:00
Documentation PM / devfreq: Add new name attribute for sysfs 2020-02-05 14:43:34 +00:00
drivers soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot 2020-02-05 14:43:41 +00:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs reiserfs: Fix memory leak of journal device string 2020-02-05 14:43:36 +00:00
include rseq: Unregister rseq for clone CLONE_VM 2020-02-05 14:43:42 +00:00
init fork: fix some -Wmissing-prototypes warnings 2019-12-05 09:21:04 +01:00
ipc ipc/mqueue.c: only perform resource calculation if user valid 2019-08-06 19:06:52 +02:00
kernel cgroup: Prevent double killing of css when enabling threaded cgroup 2020-02-05 14:43:39 +00:00
lib Partially revert "kfifo: fix kfifo_alloc() and kfifo_init()" 2020-01-27 14:51:08 +01:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm/mempolicy.c: fix out of bounds write in mpol_parse_str() 2020-02-05 14:43:36 +00:00
net Bluetooth: Fix race condition in hci_release_sock() 2020-02-05 14:43:39 +00:00
samples samples/bpf: Fix broken xdp_rxq_info due to map order assumptions 2020-01-27 14:51:22 +01:00
scripts ARM: 8950/1: ftrace/recordmcount: filter relocation types 2020-01-29 16:43:19 +01:00
security tomoyo: Use atomic_t for statistics counter 2020-02-05 14:43:38 +00:00
sound ASoC: sun4i-i2s: RX and TX counter registers are swapped 2020-01-27 14:51:05 +01:00
tools tools lib traceevent: Fix memory leakage in filter_event 2020-02-05 14:43:41 +00:00
usr kbuild: clean compressed initramfs image 2019-10-07 18:57:16 +02:00
virt KVM: arm/arm64: vgic: Don't rely on the wrong pending table 2019-12-13 08:52:45 +01:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.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 Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS USB: rio500: Remove Rio 500 kernel driver 2019-10-17 13:44:47 -07:00
Makefile Linux 4.19.101 2020-02-01 09:37:12 +00:00
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.