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Hoang Huu Le fdc1416c21 tipc: fix a deadlock when flushing scheduled work 
commit d966ddcc38 upstream.

In the commit fdeba99b1e
("tipc: fix use-after-free in tipc_bcast_get_mode"), we're trying
to make sure the tipc_net_finalize_work work item finished if it
enqueued. But calling flush_scheduled_work() is not just affecting
above work item but either any scheduled work. This has turned out
to be overkill and caused to deadlock as syzbot reported:

======================================================
WARNING: possible circular locking dependency detected
5.9.0-rc2-next-20200828-syzkaller #0 Not tainted
------------------------------------------------------
kworker/u4:6/349 is trying to acquire lock:
ffff8880aa063d38 ((wq_completion)events){+.+.}-{0:0}, at: flush_workqueue+0xe1/0x13e0 kernel/workqueue.c:2777

but task is already holding lock:
ffffffff8a879430 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x9b/0xb10 net/core/net_namespace.c:565

[...]
 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(pernet_ops_rwsem);
                               lock(&sb->s_type->i_mutex_key#13);
                               lock(pernet_ops_rwsem);
  lock((wq_completion)events);

 *** DEADLOCK ***
[...]

v1:
To fix the original issue, we replace above calling by introducing
a bit flag. When a namespace cleaned-up, bit flag is set to zero and:
- tipc_net_finalize functionial just does return immediately.
- tipc_net_finalize_work does not enqueue into the scheduled work queue.

v2:
Use cancel_work_sync() helper to make sure ONLY the
tipc_net_finalize_work() stopped before releasing bcbase object.

Reported-by: syzbot+d5aa7e0385f6a5d0f4fd@syzkaller.appspotmail.com
Fixes: fdeba99b1e ("tipc: fix use-after-free in tipc_bcast_get_mode")
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Hoang Huu Le <hoang.h.le@dektech.com.au>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-12-11 13:23:32 +01:00
Documentation dt-bindings: net: correct interrupt flags in examples 2020-12-08 10:40:25 +01:00
LICENSES
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arch x86/uprobes: Do not use prefixes.nbytes when looping over prefixes.bytes 2020-12-11 13:23:30 +01:00
block blk-cgroup: Pre-allocate tree node on blkg_conf_prep 2020-11-10 12:37:30 +01:00
certs
…
crypto crypto: algif_skcipher - EBUSY on aio should be an error 2020-10-29 09:57:30 +01:00
drivers iommu/amd: Set DTE[IntTabLen] to represent 512 IRTEs 2020-12-11 13:23:31 +01:00
fs gfs2: check for empty rgrp tree in gfs2_ri_update 2020-12-11 13:23:32 +01:00
include genirq/irqdomain: Add an irq_create_mapping_affinity() function 2020-12-11 13:23:30 +01:00
init printk: reduce LOG_BUF_SHIFT range for H8300 2020-11-05 11:43:16 +01:00
ipc
…
kernel tracing: Fix userstacktrace option for instances 2020-12-11 13:23:32 +01:00
lib lib/syscall: fix syscall registers retrieval on 32-bit platforms 2020-12-11 13:23:32 +01:00
mm mm/swapfile: do not sleep with a spin lock held 2020-12-11 13:23:31 +01:00
net tipc: fix a deadlock when flushing scheduled work 2020-12-11 13:23:32 +01:00
samples samples/bpf: Fix possible deadlock in xdpsock 2020-11-05 11:43:17 +01:00
scripts scripts/setlocalversion: make git describe output more reliable 2020-11-01 12:01:01 +01:00
security ima: extend boot_aggregate with kernel measurements 2020-12-08 10:40:24 +01:00
sound ALSA: hda/generic: Add option to enforce preferred_dacs pairs 2020-12-11 13:23:29 +01:00
tools x86/uprobes: Do not use prefixes.nbytes when looping over prefixes.bytes 2020-12-11 13:23:30 +01:00
usr
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virt KVM: arm64: vgic-v3: Drop the reporting of GICR_TYPER.Last for userspace 2020-12-02 08:49:46 +01:00
.clang-format
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.cocciconfig
…
.get_maintainer.ignore
…
.gitattributes
…
.gitignore
…
.mailmap
…
COPYING
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CREDITS
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Kbuild
…
Kconfig
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MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.82 2020-12-08 10:40:28 +01:00
README
…

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.