net: reformat kdoc return statements

kernel-doc -Wall warns about missing Return: statement for non-void
functions. We have a number of kdocs in our headers which are missing
the colon, IOW they use

net: reformat kdoc return statements

kernel-doc -Wall warns about missing Return: statement for non-void
functions. We have a number of kdocs in our headers which are missing
the colon, IOW they use
* Return some value
or
* Returns some value

Having the colon makes some sense, it should help kdoc parser avoid
false positives. So add them. This is mostly done with a sed script,
and removing the unnecessary cases (mostly the comments which aren't
kdoc).

Acked-by: Johannes Berg <[email protected]>
Acked-by: Richard Cochran <[email protected]>
Acked-by: Sergey Ryazanov <[email protected]>
Reviewed-by: Edward Cree <[email protected]>
Acked-by: Alexandra Winter <[email protected]>
Acked-by: Pablo Neira Ayuso <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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netfilter: x_tables: never register tables by default

For historical reasons x_tables still register tables by default in the
initial namespace.
Only newly created net namespaces add the hook on dem

netfilter: x_tables: never register tables by default

For historical reasons x_tables still register tables by default in the
initial namespace.
Only newly created net namespaces add the hook on demand.

This means that the init_net always pays hook cost, even if no filtering
rules are added (e.g. only used inside a single netns).

Note that the hooks are added even when 'iptables -L' is called.
This is because there is no way to tell 'iptables -A' and 'iptables -L'
apart at kernel level.

The only solution would be to register the table, but delay hook
registration until the first rule gets added (or policy gets changed).

That however means that counters are not hooked either, so 'iptables -L'
would always show 0-counters even when traffic is flowing which might be
unexpected.

This keeps table and hook registration consistent with what is already done
in non-init netns: first iptables(-save) invocation registers both table
and hooks.

This applies the same solution adopted for ebtables.
All tables register a template that contains the l3 family, the name
and a constructor function that is called when the initial table has to
be added.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: x_tables: reduce xt_action_param by 8 byte

The fragment offset in ipv4/ipv6 is a 16bit field, so use
u16 instead of unsigned int.

On 64bit: 40 bytes to 32 bytes. By extension this also r

netfilter: x_tables: reduce xt_action_param by 8 byte

The fragment offset in ipv4/ipv6 is a 16bit field, so use
u16 instead of unsigned int.

On 64bit: 40 bytes to 32 bytes. By extension this also reduces
nft_pktinfo (56 to 48 byte).

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: allow to turn off xtables compat layer

The compat layer needs to parse untrusted input (the ruleset)
to translate it to a 64bit compatible format.

We had a number of bugs in this departm

netfilter: allow to turn off xtables compat layer

The compat layer needs to parse untrusted input (the ruleset)
to translate it to a 64bit compatible format.

We had a number of bugs in this department in the past, so allow users
to turn this feature off.

Add CONFIG_NETFILTER_XTABLES_COMPAT kconfig knob and make it default to y
to keep existing behaviour.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: ip_tables: pass table pointer via nf_hook_ops

iptable_x modules rely on 'struct net' to contain a pointer to the
table that should be evaluated.

In order to remove these pointers from st

netfilter: ip_tables: pass table pointer via nf_hook_ops

iptable_x modules rely on 'struct net' to contain a pointer to the
table that should be evaluated.

In order to remove these pointers from struct net, pass them via
the 'priv' pointer in a similar fashion as nf_tables passes the
rule data.

To do that, duplicate the nf_hook_info array passed in from the
iptable_x modules, update the ops->priv pointers of the copy to
refer to the table and then change the hookfn implementations to
just pass the 'priv' argument to the traverser.

After this patch, the xt_table pointers can already be removed
from struct net.

However, changes to struct net result in re-compile of the entire
network stack, so do the removal after arptables and ip6tables
have been converted as well.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: x_tables: add xt_find_table

This will be used to obtain the xt_table struct given address family and
table name.

Followup patches will reduce the number of direct accesses to the xt_tabl

netfilter: x_tables: add xt_find_table

This will be used to obtain the xt_table struct given address family and
table name.

Followup patches will reduce the number of direct accesses to the xt_table
structures via net->ipv{4,6}.ip(6)table_{nat,mangle,...} pointers, then
remove them.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: x_tables: Use correct memory barriers.

When a new table value was assigned, it was followed by a write memory
barrier. This ensured that all writes before this point would complete
before

netfilter: x_tables: Use correct memory barriers.

When a new table value was assigned, it was followed by a write memory
barrier. This ensured that all writes before this point would complete
before any writes after this point. However, to determine whether the
rules are unused, the sequence counter is read. To ensure that all
writes have been done before these reads, a full memory barrier is
needed, not just a write memory barrier. The same argument applies when
incrementing the counter, before the rules are read.

Changing to using smp_mb() instead of smp_wmb() fixes the kernel panic
reported in cc00bcaa5899 (which is still present), while still
maintaining the same speed of replacing tables.

The smb_mb() barriers potentially slow the packet path, however testing
has shown no measurable change in performance on a 4-core MIPS64
platform.

Fixes: 7f5c6d4f665b ("netfilter: get rid of atomic ops in fast path")
Signed-off-by: Mark Tomlinson <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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Revert "netfilter: x_tables: Switch synchronization to RCU"

This reverts commit cc00bcaa589914096edef7fb87ca5cee4a166b5c.

This (and the preceding) patch basically re-implemented the RCU
mechanisms

Revert "netfilter: x_tables: Switch synchronization to RCU"

This reverts commit cc00bcaa589914096edef7fb87ca5cee4a166b5c.

This (and the preceding) patch basically re-implemented the RCU
mechanisms of patch 784544739a25. That patch was replaced because of the
performance problems that it created when replacing tables. Now, we have
the same issue: the call to synchronize_rcu() makes replacing tables
slower by as much as an order of magnitude.

Prior to using RCU a script calling "iptables" approx. 200 times was
taking 1.16s. With RCU this increased to 11.59s.

Revert these patches and fix the issue in a different way.

Signed-off-by: Mark Tomlinson <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: x_tables: Switch synchronization to RCU

When running concurrent iptables rules replacement with data, the per CPU
sequence count is checked after the assignment of the new information.
Th

netfilter: x_tables: Switch synchronization to RCU

When running concurrent iptables rules replacement with data, the per CPU
sequence count is checked after the assignment of the new information.
The sequence count is used to synchronize with the packet path without the
use of any explicit locking. If there are any packets in the packet path using
the table information, the sequence count is incremented to an odd value and
is incremented to an even after the packet process completion.

The new table value assignment is followed by a write memory barrier so every
CPU should see the latest value. If the packet path has started with the old
table information, the sequence counter will be odd and the iptables
replacement will wait till the sequence count is even prior to freeing the
old table info.

However, this assumes that the new table information assignment and the memory
barrier is actually executed prior to the counter check in the replacement
thread. If CPU decides to execute the assignment later as there is no user of
the table information prior to the sequence check, the packet path in another
CPU may use the old table information. The replacement thread would then free
the table information under it leading to a use after free in the packet
processing context-

Unable to handle kernel NULL pointer dereference at virtual
address 000000000000008e
pc : ip6t_do_table+0x5d0/0x89c
lr : ip6t_do_table+0x5b8/0x89c
ip6t_do_table+0x5d0/0x89c
ip6table_filter_hook+0x24/0x30
nf_hook_slow+0x84/0x120
ip6_input+0x74/0xe0
ip6_rcv_finish+0x7c/0x128
ipv6_rcv+0xac/0xe4
__netif_receive_skb+0x84/0x17c
process_backlog+0x15c/0x1b8
napi_poll+0x88/0x284
net_rx_action+0xbc/0x23c
__do_softirq+0x20c/0x48c

This could be fixed by forcing instruction order after the new table
information assignment or by switching to RCU for the synchronization.

Fixes: 80055dab5de0 ("netfilter: x_tables: make xt_replace_table wait until old rules are not used anymore")
Reported-by: Sean Tranchetti <[email protected]>
Reported-by: kernel test robot <[email protected]>
Suggested-by: Florian Westphal <[email protected]>
Signed-off-by: Subash Abhinov Kasiviswanathan <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: switch xt_copy_counters to sockptr_t

Pass a sockptr_t to prepare for set_fs-less handling of the kernel
pointer from bpf-cgroup.

Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-

netfilter: switch xt_copy_counters to sockptr_t

Pass a sockptr_t to prepare for set_fs-less handling of the kernel
pointer from bpf-cgroup.

Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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netfilter: remove the compat argument to xt_copy_counters_from_user

Lift the in_compat_syscall() from the callers instead.

Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: David S. Mill

netfilter: remove the compat argument to xt_copy_counters_from_user

Lift the in_compat_syscall() from the callers instead.

Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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netfilter: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare

netfilter: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
int stuff;
struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

Lastly, fix checkpatch.pl warning
WARNING: __aligned(size) is preferred over __attribute__((aligned(size)))
in net/bridge/netfilter/ebtables.c

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: remove CONFIG_NETFILTER checks from headers.

`struct nf_hook_ops`, `struct nf_hook_state` and the `nf_hookfn`
function typedef appear in function and struct declarations and
definitions i

netfilter: remove CONFIG_NETFILTER checks from headers.

`struct nf_hook_ops`, `struct nf_hook_state` and the `nf_hookfn`
function typedef appear in function and struct declarations and
definitions in a number of netfilter headers. The structs and typedef
themselves are defined by linux/netfilter.h but only when
CONFIG_NETFILTER is enabled. Define them unconditionally and add
forward declarations in order to remove CONFIG_NETFILTER conditionals
from the other headers.

Signed-off-by: Jeremy Sowden <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: fix coding-style errors.

Several header-files, Kconfig files and Makefiles have trailing
white-space. Remove it.

In netfilter/Kconfig, indent the type of CONFIG_NETFILTER_NETLINK_ACCT
c

netfilter: fix coding-style errors.

Several header-files, Kconfig files and Makefiles have trailing
white-space. Remove it.

In netfilter/Kconfig, indent the type of CONFIG_NETFILTER_NETLINK_ACCT
correctly.

There are semicolons at the end of two function definitions in
include/net/netfilter/nf_conntrack_acct.h and
include/net/netfilter/nf_conntrack_ecache.h. Remove them.

Fix indentation in nf_conntrack_l4proto.h.

Signed-off-by: Jeremy Sowden <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: add missing IS_ENABLED(CONFIG_NETFILTER) checks to some header-files.

linux/netfilter.h defines a number of struct and inline function
definitions which are only available is CONFIG_NETFI

netfilter: add missing IS_ENABLED(CONFIG_NETFILTER) checks to some header-files.

linux/netfilter.h defines a number of struct and inline function
definitions which are only available is CONFIG_NETFILTER is enabled.
These structs and functions are used in declarations and definitions in
other header-files. Added preprocessor checks to make sure these
headers will compile if CONFIG_NETFILTER is disabled.

Signed-off-by: Jeremy Sowden <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: make two functions static

They have no external callers anymore.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

netfilter: convert the proto argument from u8 to u16

The proto in struct xt_match and struct xt_target is u16, when
calling xt_check_target/match, their proto argument is u8,
and will cause truncati

netfilter: convert the proto argument from u8 to u16

The proto in struct xt_match and struct xt_target is u16, when
calling xt_check_target/match, their proto argument is u8,
and will cause truncation, it is harmless to ip packet, since
ip proto is u8

if a etable's match/target has proto that is u16, will cause
the check failure.

and convert be16 to short in bridge/netfilter/ebtables.c

Signed-off-by: Zhang Yu <[email protected]>
Signed-off-by: Li RongQing <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: x_tables: add and use xt_check_proc_name

recent and hashlimit both create /proc files, but only check that
name is 0 terminated.

This can trigger WARN() from procfs when name is "" or "/

netfilter: x_tables: add and use xt_check_proc_name

recent and hashlimit both create /proc files, but only check that
name is 0 terminated.

This can trigger WARN() from procfs when name is "" or "/".
Add helper for this and then use it for both.

Cc: Eric Dumazet <[email protected]>
Reported-by: Eric Dumazet <[email protected]>
Reported-by: <[email protected]>
Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: compat: prepare xt_compat_init_offsets to return errors

should have no impact, function still always returns 0.
This patch is only to ease review.

Signed-off-by: Florian Westphal <fw@str

netfilter: compat: prepare xt_compat_init_offsets to return errors

should have no impact, function still always returns 0.
This patch is only to ease review.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: x_tables: add counters allocation wrapper

allows to have size checks in a single spot.
This is supposed to reduce oom situations when fuzz-testing xtables.

Signed-off-by: Florian Westpha

netfilter: x_tables: add counters allocation wrapper

allows to have size checks in a single spot.
This is supposed to reduce oom situations when fuzz-testing xtables.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: x_tables: move hook entry checks into core

Allow followup patch to change on location instead of three.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <p

netfilter: x_tables: move hook entry checks into core

Allow followup patch to change on location instead of three.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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netfilter: xtables: add and use xt_request_find_table_lock

currently we always return -ENOENT to userspace if we can't find
a particular table, or if the table initialization fails.

Followup patch

netfilter: xtables: add and use xt_request_find_table_lock

currently we always return -ENOENT to userspace if we can't find
a particular table, or if the table initialization fails.

Followup patch will make nat table init fail in case nftables already
registered a nat hook so this change makes xt_find_table_lock return
an ERR_PTR to return the errno value reported from the table init
function.

Add xt_request_find_table_lock as try_then_request_module replacement
and use it where needed.

Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <[email protected]>
Reviewed-by: Philippe Ombredanne <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

show more ...

netfilter: xtables: zero padding in data_to_user

When looking up an iptables rule, the iptables binary compares the
aligned match and target data (XT_ALIGN). In some cases this can
exceed the actual

netfilter: xtables: zero padding in data_to_user

When looking up an iptables rule, the iptables binary compares the
aligned match and target data (XT_ALIGN). In some cases this can
exceed the actual data size to include padding bytes.

Before commit f77bc5b23fb1 ("iptables: use match, target and data
copy_to_user helpers") the malloc()ed bytes were overwritten by the
kernel with kzalloced contents, zeroing the padding and making the
comparison succeed. After this patch, the kernel copies and clears
only data, leaving the padding bytes undefined.

Extend the clear operation from data size to aligned data size to
include the padding bytes, if any.

Padding bytes can be observed in both match and target, and the bug
triggered, by issuing a rule with match icmp and target ACCEPT:

iptables -t mangle -A INPUT -i lo -p icmp --icmp-type 1 -j ACCEPT
iptables -t mangle -D INPUT -i lo -p icmp --icmp-type 1 -j ACCEPT

Fixes: f77bc5b23fb1 ("iptables: use match, target and data copy_to_user helpers")
Reported-by: Paul Moore <[email protected]>
Reported-by: Richard Guy Briggs <[email protected]>
Signed-off-by: Willem de Bruijn <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

show more ...

xtables: add xt_match, xt_target and data copy_to_user functions

xt_entry_target, xt_entry_match and their private data may contain
kernel data.

Introduce helper functions xt_match_to_user, xt_targ

xtables: add xt_match, xt_target and data copy_to_user functions

xt_entry_target, xt_entry_match and their private data may contain
kernel data.

Introduce helper functions xt_match_to_user, xt_target_to_user and
xt_data_to_user that copy only the expected fields. These replace
existing logic that calls copy_to_user on entire structs, then
overwrites select fields.

Private data is defined in xt_match and xt_target. All matches and
targets that maintain kernel data store this at the tail of their
private structure. Extend xt_match and xt_target with .usersize to
limit how many bytes of data are copied. The remainder is cleared.

If compatsize is specified, usersize can only safely be used if all
fields up to usersize use platform-independent types. Otherwise, the
compat_to_user callback must be defined.

This patch does not yet enable the support logic.

Signed-off-by: Willem de Bruijn <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

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