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Yonghong Song fd1e31d1bc selftests/bpf: Workaround verification failure for fexit_bpf2bpf/func_replace_return_code 
[ Upstream commit 63d78b7e8c ]

With latest llvm17, selftest fexit_bpf2bpf/func_replace_return_code
has the following verification failure:

  0: R1=ctx(off=0,imm=0) R10=fp0
  ; int connect_v4_prog(struct bpf_sock_addr *ctx)
  0: (bf) r7 = r1                       ; R1=ctx(off=0,imm=0) R7_w=ctx(off=0,imm=0)
  1: (b4) w6 = 0                        ; R6_w=0
  ; memset(&tuple.ipv4.saddr, 0, sizeof(tuple.ipv4.saddr));
  ...
  ; return do_bind(ctx) ? 1 : 0;
  179: (bf) r1 = r7                     ; R1=ctx(off=0,imm=0) R7=ctx(off=0,imm=0)
  180: (85) call pc+147
  Func#3 is global and valid. Skipping.
  181: R0_w=scalar()
  181: (bc) w6 = w0                     ; R0_w=scalar() R6_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff))
  182: (05) goto pc-129
  ; }
  54: (bc) w0 = w6                      ; R0_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R6_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff))
  55: (95) exit
  At program exit the register R0 has value (0x0; 0xffffffff) should have been in (0x0; 0x1)
  processed 281 insns (limit 1000000) max_states_per_insn 1 total_states 26 peak_states 26 mark_read 13
  -- END PROG LOAD LOG --
  libbpf: prog 'connect_v4_prog': failed to load: -22

The corresponding source code:

  __attribute__ ((noinline))
  int do_bind(struct bpf_sock_addr *ctx)
  {
        struct sockaddr_in sa = {};

        sa.sin_family = AF_INET;
        sa.sin_port = bpf_htons(0);
        sa.sin_addr.s_addr = bpf_htonl(SRC_REWRITE_IP4);

        if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
                return 0;

        return 1;
  }
  ...
  SEC("cgroup/connect4")
  int connect_v4_prog(struct bpf_sock_addr *ctx)
  {
  ...
        return do_bind(ctx) ? 1 : 0;
  }

Insn 180 is a call to 'do_bind'. The call's return value is also the return value
for the program. Since do_bind() returns 0/1, so it is legitimate for compiler to
optimize 'return do_bind(ctx) ? 1 : 0' to 'return do_bind(ctx)'. However, such
optimization breaks verifier as the return value of 'do_bind()' is marked as any
scalar which violates the requirement of prog return value 0/1.

There are two ways to fix this problem, (1) changing 'return 1' in do_bind() to
e.g. 'return 10' so the compiler has to do 'do_bind(ctx) ? 1 :0', or (2)
suggested by Andrii, marking do_bind() with __weak attribute so the compiler
cannot make any assumption on do_bind() return value.

This patch adopted adding __weak approach which is simpler and more resistant
to potential compiler optimizations.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230310012410.2920570-1-yhs@fb.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-07-27 08:50:51 +02:00
arch bpf, arm64: Fix BTI type used for freplace attached functions 2023-07-27 08:50:44 +02:00
block blk-crypto: use dynamic lock class for blk_crypto_profile::lock 2023-07-23 13:49:21 +02:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: jitter - correct health test during initialization 2023-07-19 16:21:42 +02:00
Documentation sched/psi: Allow unprivileged polling of N*2s period 2023-07-27 08:50:38 +02:00
drivers spi: dw: Remove misleading comment for Mount Evans SoC 2023-07-27 08:50:50 +02:00
fs jbd2: recheck chechpointing non-dirty buffer 2023-07-27 08:50:49 +02:00
include tcp: annotate data-races around fastopenq.max_qlen 2023-07-27 08:50:49 +02:00
init gcc: disable '-Warray-bounds' for gcc-13 too 2023-04-26 14:28:43 +02:00
io_uring io_uring: treat -EAGAIN for REQ_F_NOWAIT as final for io-wq 2023-07-27 08:50:23 +02:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel bpf: aggressively forget precise markings during state checkpointing 2023-07-27 08:50:51 +02:00
lib maple_tree: set the node limit when creating a new root node 2023-07-27 08:50:24 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm kasan: add kasan_tag_mismatch prototype 2023-07-23 13:49:32 +02:00
net tcp: annotate data-races around fastopenq.max_qlen 2023-07-27 08:50:49 +02:00
rust rust: kernel: Mark rust_fmt_argument as extern "C" 2023-04-26 14:28:38 +02:00
samples samples: ftrace: Save required argument registers in sample trampolines 2023-07-23 13:49:44 +02:00
scripts scripts/kallsyms: update the usage in the comment block 2023-07-27 08:50:50 +02:00
security security: keys: Modify mismatched function name 2023-07-27 08:50:43 +02:00
sound ALSA: hda/realtek: Fix generic fixup definition for cs35l41 amp 2023-07-27 08:50:46 +02:00
tools selftests/bpf: Workaround verification failure for fexit_bpf2bpf/func_replace_return_code 2023-07-27 08:50:51 +02:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Avoid illegal stage2 mapping on invalid memory slot 2023-06-28 11:12:23 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS smb: move client and server files to common directory fs/smb 2023-06-28 11:12:40 +02:00
Makefile Linux 6.1.41 2023-07-24 18:55:35 +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.