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Miklos Szeredi 5d6d3a301c fuse: allow server to run in different pid_ns
Commit 0b6e9ea041 ("fuse: Add support for pid namespaces") broke
Sandstorm.io development tools, which have been sending FUSE file
descriptors across PID namespace boundaries since early 2014.

The above patch added a check that prevented I/O on the fuse device file
descriptor if the pid namespace of the reader/writer was different from the
pid namespace of the mounter.  With this change passing the device file
descriptor to a different pid namespace simply doesn't work.  The check was
added because pids are transferred to/from the fuse userspace server in the
namespace registered at mount time.

To fix this regression, remove the checks and do the following:

1) the pid in the request header (the pid of the task that initiated the
filesystem operation) is translated to the reader's pid namespace.  If a
mapping doesn't exist for this pid, then a zero pid is used.  Note: even if
a mapping would exist between the initiator task's pid namespace and the
reader's pid namespace the pid will be zero if either mapping from
initator's to mounter's namespace or mapping from mounter's to reader's
namespace doesn't exist.

2) The lk.pid value in setlk/setlkw requests and getlk reply is left alone.
Userspace should not interpret this value anyway.  Also allow the
setlk/setlkw operations if the pid of the task cannot be represented in the
mounter's namespace (pid being zero in that case).

Reported-by: Kenton Varda <kenton@sandstorm.io>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 0b6e9ea041 ("fuse: Add support for pid namespaces")
Cc: <stable@vger.kernel.org> # v4.12+
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Seth Forshee <seth.forshee@canonical.com>
2017-09-12 16:57:53 +02:00
arch Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2017-09-03 09:50:26 -07:00
block blk-mq-debugfs: Add names for recently added flags 2017-08-25 08:07:44 -06:00
certs modsign: add markers to endif-statements in certs/Makefile 2017-07-14 11:01:37 +10:00
crypto crypto: algif_skcipher - only call put_page on referenced and used pages 2017-08-22 14:45:48 +08:00
Documentation ARM: SoC fixes for 4.13 2017-09-01 17:16:40 -07:00
drivers Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2017-09-03 09:50:26 -07:00
firmware firmware/Makefile: force recompilation if makefile changes 2017-05-08 17:15:10 -07:00
fs fuse: allow server to run in different pid_ns 2017-09-12 16:57:53 +02:00
include Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-03 09:23:23 -07:00
init random: do not ignore early device randomness 2017-07-12 16:26:00 -07:00
ipc ipc: add missing container_of()s for randstruct 2017-08-02 17:16:12 -07:00
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-03 09:30:40 -07:00
lib Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-09-01 10:30:03 -07:00
mm Merge branch 'akpm' (patches from Andrew) 2017-08-31 17:56:56 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-09-01 12:49:03 -07:00
samples samples/bpf: fix bpf tunnel cleanup 2017-07-31 22:02:47 -07:00
scripts scripts/dtc: fix '%zx' warning 2017-08-31 16:33:15 -07:00
security Now that IPC and other changes have landed, enable manual markings for 2017-07-19 08:55:18 -07:00
sound ASoC: Fixes for v4.13 2017-08-31 14:08:26 +02:00
tools NTB bug fixes to address an incorrect ntb_mw_count reference in the NTB 2017-08-27 17:01:54 -07:00
usr ramfs: clarify help text that compression applies to ramfs as well as legacy ramdisk. 2017-07-06 16:24:30 -07:00
virt KVM: update to new mmu_notifier semantic v2 2017-08-31 16:13:00 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap power supply and reset changes for the v4.12 series (part 2) 2017-05-12 12:02:21 -07:00
COPYING
CREDITS avr32: remove support for AVR32 architecture 2017-05-01 09:27:15 +02:00
Kbuild kbuild: Consolidate header generation from ASM offset information 2017-04-13 05:43:37 +09:00
Kconfig
MAINTAINERS Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-08-20 09:07:56 -07:00
Makefile Linux 4.13 2017-09-03 13:56:17 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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.