Signed-off-by: NStephen Hemminger <stephen@networkplumber.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

What we want here is to embed a user-space program into the kernel.
Instead of the complex ELF magic, let's simply wrap it in the assembly
with the '.incbin' directive.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

With the brand-new syntax extension of Kconfig, we can directly
check the compiler capability in the configuration phase.

If the cc-can-link.sh fails, the BPFILTER_UMH is automatically
hidden by the dependency.

I also deleted 'default n', which is no-op.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Use $(OBJDUMP) instead of literal 'objdump' to avoid
using host toolchain when cross compiling.

Fixes: 421780fd ("bpfilter: fix build error")
Signed-off-by: NMatteo Croce <mcroce@redhat.com>
Reported-by: NStefano Brivio <sbrivio@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/bpfilter/bpfilter_umh is a binary file generated when bpfilter is
enabled, add it to .gitignore to avoid committing it.

Fixes: d2ba09c1 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: NMatteo Croce <mcroce@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

bpfilter Makefile assumes that the system locale is en_US, and the
parsing of objdump output fails.
Set LC_ALL=C and, while at it, rewrite the objdump parsing so it spawns
only 2 processes instead of 7.

Fixes: d2ba09c1 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: NMatteo Croce <mcroce@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

syzbot reported the following crash
[  338.293946] bpfilter: read fail -512
[  338.304515] kasan: GPF could be caused by NULL-ptr deref or user memory access
[  338.311863] general protection fault: 0000 [#1] SMP KASAN
[  338.344360] RIP: 0010:__vfs_write+0x4a6/0x960
[  338.426363] Call Trace:
[  338.456967]  __kernel_write+0x10c/0x380
[  338.460928]  __bpfilter_process_sockopt+0x1d8/0x35b
[  338.487103]  bpfilter_mbox_request+0x4d/0xb0
[  338.491492]  bpfilter_ip_get_sockopt+0x6b/0x90

This can happen when multiple cpus trying to talk to user mode process
via bpfilter_mbox_request(). One cpu grabs the mutex while another goes to
sleep on the same mutex. Then former cpu sees that umh pipe is down and
shuts down the pipes. Later cpu finally acquires the mutex and crashes
on freed pipe.
Fix the race by using info.pid as an indicator that umh and pipes are healthy
and check it after acquiring the mutex.

Fixes: d2ba09c1 ("net: add skeleton of bpfilter kernel module")
Reported-by: syzbot+7ade6c94abb2774c0fee@syzkaller.appspotmail.com
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

CONFIG_OUTPUT_FORMAT is x86 only macro.
Used objdump to extract elf file format.

Fixes: d2ba09c1 ("net: add skeleton of bpfilter kernel module")
Reported-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

check that CC can build executables and use that compiler instead of HOSTCC
Suggested-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

gcc-7.3.0 report following err:

  HOSTCC  net/bpfilter/main.o
In file included from net/bpfilter/main.c:9:0:
./include/uapi/linux/bpf.h:12:10: fatal error: linux/bpf_common.h: No such file or directory
 #include <linux/bpf_common.h>

remove it by adding a include path.
Fixes: d2ba09c1 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

bpfilter_process_sockopt is a callback that gets called from
ip_setsockopt() and ip_getsockopt(). However, when CONFIG_INET is
disabled, it never gets called at all, and assigning a function to the
callback pointer results in a link failure:

net/bpfilter/bpfilter_kern.o: In function `__stop_umh':
bpfilter_kern.c:(.text.unlikely+0x3): undefined reference to `bpfilter_process_sockopt'
net/bpfilter/bpfilter_kern.o: In function `load_umh':
bpfilter_kern.c:(.init.text+0x73): undefined reference to `bpfilter_process_sockopt'

Since there is no caller in this configuration, I assume we can
simply make the assignment conditional.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Passing O_CREAT (00000100) to open means we should also pass file
mode as the third parameter.  Creating /dev/console as a regular
file may not be helpful anyway, so simply drop the flag when
opening debug_fd.

Fixes: d2ba09c1 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

BPFILTER could have been enabled without INET causing this build error:
ERROR: "bpfilter_process_sockopt" [net/bpfilter/bpfilter.ko] undefined!

Fixes: d2ba09c1 ("net: add skeleton of bpfilter kernel module")
Reported-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

bpfilter.ko consists of bpfilter_kern.c (normal kernel module code)
and user mode helper code that is embedded into bpfilter.ko

The steps to build bpfilter.ko are the following:
- main.c is compiled by HOSTCC into the bpfilter_umh elf executable file
- with quite a bit of objcopy and Makefile magic the bpfilter_umh elf file
  is converted into bpfilter_umh.o object file
  with _binary_net_bpfilter_bpfilter_umh_start and _end symbols
  Example:
  $ nm ./bld_x64/net/bpfilter/bpfilter_umh.o
  0000000000004cf8 T _binary_net_bpfilter_bpfilter_umh_end
  0000000000004cf8 A _binary_net_bpfilter_bpfilter_umh_size
  0000000000000000 T _binary_net_bpfilter_bpfilter_umh_start
- bpfilter_umh.o and bpfilter_kern.o are linked together into bpfilter.ko

bpfilter_kern.c is a normal kernel module code that calls
the fork_usermode_blob() helper to execute part of its own data
as a user mode process.

Notice that _binary_net_bpfilter_bpfilter_umh_start - end
is placed into .init.rodata section, so it's freed as soon as __init
function of bpfilter.ko is finished.
As part of __init the bpfilter.ko does first request/reply action
via two unix pipe provided by fork_usermode_blob() helper to
make sure that umh is healthy. If not it will kill it via pid.

Later bpfilter_process_sockopt() will be called from bpfilter hooks
in get/setsockopt() to pass iptable commands into umh via bpfilter.ko

If admin does 'rmmod bpfilter' the __exit code bpfilter.ko will
kill umh as well.
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>