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zhuoliang zhang 5cb904da85 net: xfrm: fix a race condition during allocing spi 
[ Upstream commit a779d91314 ]

we found that the following race condition exists in
xfrm_alloc_userspi flow:

user thread                                    state_hash_work thread
----                                           ----
xfrm_alloc_userspi()
 __find_acq_core()
   /*alloc new xfrm_state:x*/
   xfrm_state_alloc()
   /*schedule state_hash_work thread*/
   xfrm_hash_grow_check()   	               xfrm_hash_resize()
 xfrm_alloc_spi                                  /*hold lock*/
      x->id.spi = htonl(spi)                     spin_lock_bh(&net->xfrm.xfrm_state_lock)
      /*waiting lock release*/                     xfrm_hash_transfer()
      spin_lock_bh(&net->xfrm.xfrm_state_lock)      /*add x into hlist:net->xfrm.state_byspi*/
	                                                hlist_add_head_rcu(&x->byspi)
                                                 spin_unlock_bh(&net->xfrm.xfrm_state_lock)

    /*add x into hlist:net->xfrm.state_byspi 2 times*/
    hlist_add_head_rcu(&x->byspi)

1. a new state x is alloced in xfrm_state_alloc() and added into the bydst hlist
in  __find_acq_core() on the LHS;
2. on the RHS, state_hash_work thread travels the old bydst and tranfers every xfrm_state
(include x) into the new bydst hlist and new byspi hlist;
3. user thread on the LHS gets the lock and adds x into the new byspi hlist again.

So the same xfrm_state (x) is added into the same list_hash
(net->xfrm.state_byspi) 2 times that makes the list_hash become
an inifite loop.

To fix the race, x->id.spi = htonl(spi) in the xfrm_alloc_spi() is moved
to the back of spin_lock_bh, sothat state_hash_work thread no longer add x
which id.spi is zero into the hash_list.

Fixes: f034b5d4ef ("[XFRM]: Dynamic xfrm_state hash table sizing.")
Signed-off-by: zhuoliang zhang <zhuoliang.zhang@mediatek.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2020-11-18 19:20:17 +01:00
Documentation linkage: Introduce new macros for assembler symbols 2020-11-10 12:37:24 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch arm64: dts: marvell: espressobin: Add ethernet switch aliases 2020-11-10 12:37:34 +01:00
block blk-cgroup: Pre-allocate tree node on blkg_conf_prep 2020-11-10 12:37:30 +01:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: algif_skcipher - EBUSY on aio should be an error 2020-10-29 09:57:30 +01:00
drivers hv_balloon: disable warning when floor reached 2020-11-18 19:20:17 +01:00
fs btrfs: reschedule when cloning lots of extents 2020-11-18 19:20:16 +01:00
include btrfs: tracepoints: output proper root owner for trace_find_free_extent() 2020-11-18 19:20:16 +01:00
init printk: reduce LOG_BUF_SHIFT range for H8300 2020-11-05 11:43:16 +01:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel genirq: Let GENERIC_IRQ_IPI select IRQ_DOMAIN_HIERARCHY 2020-11-18 19:20:16 +01:00
lib lib/crc32test: remove extra local_irq_disable/enable 2020-11-10 12:37:27 +01:00
mm mm: mempolicy: fix potential pte_unmap_unlock pte error 2020-11-10 12:37:27 +01:00
net net: xfrm: fix a race condition during allocing spi 2020-11-18 19:20:17 +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 evm: Check size of security.evm before using it 2020-11-01 12:01:05 +01:00
sound ASoC: Intel: kbl_rt5663_max98927: Fix kabylake_ssp_fixup function 2020-11-18 19:20:16 +01:00
tools perf python scripting: Fix printable strings in python3 scripts 2020-11-05 11:43:32 +01:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: Force PTE mapping on fault resulting in a device mapping 2020-11-18 19:20:15 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
…
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.77 2020-11-10 21:13:20 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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.

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.