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Sergey Marinkevich 4bf1941581 netfilter: nft_exthdr: fix endianness of tcp option cast 
[ Upstream commit 2e34328b39 ]

I got a problem on MIPS with Big-Endian is turned on: every time when
NF trying to change TCP MSS it returns because of new.v16 was greater
than old.v16. But real MSS was 1460 and my rule was like this:

	add rule table chain tcp option maxseg size set 1400

And 1400 is lesser that 1460, not greater.

Later I founded that main causer is cast from u32 to __be16.

Debugging:

In example MSS = 1400(HEX: 0x578). Here is representation of each byte
like it is in memory by addresses from left to right(e.g. [0x0 0x1 0x2
0x3]). LE — Little-Endian system, BE — Big-Endian, left column is type.

	     LE               BE
	u32: [78 05 00 00]    [00 00 05 78]

As you can see, u32 representation will be casted to u16 from different
half of 4-byte address range. But actually nf_tables uses registers and
store data of various size. Actually TCP MSS stored in 2 bytes. But
registers are still u32 in definition:

	struct nft_regs {
		union {
			u32			data[20];
			struct nft_verdict	verdict;
		};
	};

So, access like regs->data[priv->sreg] exactly u32. So, according to
table presents above, per-byte representation of stored TCP MSS in
register will be:

	                     LE               BE
	(u32)regs->data[]:   [78 05 00 00]    [05 78 00 00]
	                                       ^^ ^^

We see that register uses just half of u32 and other 2 bytes may be
used for some another data. But in nft_exthdr_tcp_set_eval() it casted
just like u32 -> __be16:

	new.v16 = src

But u32 overfill __be16, so it get 2 low bytes. For clarity draw
one more table(<xx xx> means that bytes will be used for cast).

	                     LE                 BE
	u32:                 [<78 05> 00 00]    [00 00 <05 78>]
	(u32)regs->data[]:   [<78 05> 00 00]    [05 78 <00 00>]

As you can see, for Little-Endian nothing changes, but for Big-endian we
take the wrong half. In my case there is some other data instead of
zeros, so new MSS was wrongly greater.

For shooting this bug I used solution for ports ranges. Applying of this
patch does not affect Little-Endian systems.

Signed-off-by: Sergey Marinkevich <sergey.marinkevich@eltex-co.ru>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-08-26 08:36:22 -04:00
arch ARM: dts: nomadik: Fix up interrupt controller node names 2021-08-26 08:36:14 -04:00
block blk-iolatency: error out if blk_get_queue() failed in iolatency_set_limit() 2021-08-12 13:20:58 +02:00
certs certs: Move load_system_certificate_list to a common function 2021-06-30 08:47:55 -04:00
crypto crypto: shash - avoid comparing pointers to exported functions under CFI 2021-07-14 16:53:13 +02:00
Documentation KVM: X86: MMU: Use the correct inherited permissions to get shadow page 2021-08-15 13:08:04 +02:00
drivers PCI: Increase D3 delay for AMD Renoir/Cezanne XHCI 2021-08-26 08:36:21 -04:00
fs fs: warn about impending deprecation of mandatory locks 2021-08-26 08:36:22 -04:00
include mm: memcontrol: fix occasional OOMs due to proportional memory.low reclaim 2021-08-26 08:36:22 -04:00
init kbuild: add CONFIG_LD_IS_LLD 2021-06-30 08:47:44 -04:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel tracing / histogram: Fix NULL pointer dereference on strcmp() on NULL event name 2021-08-26 08:36:20 -04:00
lib lib/decompress_unlz4.c: correctly handle zero-padding around initrds. 2021-07-20 16:10:46 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm: memcontrol: fix occasional OOMs due to proportional memory.low reclaim 2021-08-26 08:36:22 -04:00
net netfilter: nft_exthdr: fix endianness of tcp option cast 2021-08-26 08:36:22 -04:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-14 16:53:30 +02:00
scripts scripts/tracing: fix the bug that can't parse raw_trace_func 2021-08-12 13:21:00 +02:00
security smackfs: restrict bytes count in smk_set_cipso() 2021-07-19 08:53:18 +02:00
sound ASoC: intel: atom: Fix breakage for PCM buffer address setup 2021-08-26 08:36:21 -04:00
tools bpf, selftests: Adjust few selftest result_unpriv outcomes 2021-08-12 13:21:04 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: Do not leak memory for duplicate debugfs directories 2021-08-12 13:21:03 +02:00
.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
.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 5.4.142 2021-08-18 08:57:05 +02:00
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.