Commit 899832d8 authored Jun 15, 2023 by Florent Revest Committed by sanglipeng Nov 30, 2023

bpf/btf: Accept function names that contain dots

stable inclusion
from stable-v5.10.186
commit 29917a20be438602e5a1042a639e7d9af9db5bdc
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8J4KH

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29917a20be438602e5a1042a639e7d9af9db5bdc



--------------------------------

[ Upstream commit 9724160b ]

When building a kernel with LLVM=1, LLVM_IAS=0 and CONFIG_KASAN=y, LLVM
leaves DWARF tags for the "asan.module_ctor" & co symbols. In turn,
pahole creates BTF_KIND_FUNC entries for these and this makes the BTF
metadata validation fail because they contain a dot.

In a dramatic turn of event, this BTF verification failure can cause
the netfilter_bpf initialization to fail, causing netfilter_core to
free the netfilter_helper hashmap and netfilter_ftp to trigger a
use-after-free. The risk of u-a-f in netfilter will be addressed
separately but the existence of "asan.module_ctor" debug info under some
build conditions sounds like a good enough reason to accept functions
that contain dots in BTF.

Although using only LLVM=1 is the recommended way to compile clang-based
kernels, users can certainly do LLVM=1, LLVM_IAS=0 as well and we still
try to support that combination according to Nick. To clarify:

  - > v5.10 kernel, LLVM=1 (LLVM_IAS=0 is not the default) is recommended,
    but user can still have LLVM=1, LLVM_IAS=0 to trigger the issue

  - <= 5.10 kernel, LLVM=1 (LLVM_IAS=0 is the default) is recommended in
    which case GNU as will be used

Fixes: 1dc92851 ("bpf: kernel side support for BTF Var and DataSec")
Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Cc: Yonghong Song <yhs@meta.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/bpf/20230615145607.3469985-1-revest@chromium.org


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>

parent 3716b55b

kernel/bpf/btf.c

+8 −12

Original line number	Diff line number	Diff line
		@@ -604,31 +604,30 @@ static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
		offset < btf->hdr.str_len;
		}

		static bool __btf_name_char_ok(char c, bool first, bool dot_ok)
		static bool __btf_name_char_ok(char c, bool first)
		{
		if ((first ? !isalpha(c) :
		!isalnum(c)) &&
		c != '_' &&
		((c == '.' && !dot_ok) \|\|
		c != '.'))
		c != '.')
		return false;
		return true;
		}

		static bool __btf_name_valid(const struct btf *btf, u32 offset, bool dot_ok)
		static bool __btf_name_valid(const struct btf *btf, u32 offset)
		{
		/* offset must be valid */
		const char *src = &btf->strings[offset];
		const char *src_limit;

		if (!__btf_name_char_ok(*src, true, dot_ok))
		if (!__btf_name_char_ok(*src, true))
		return false;

		/* set a limit on identifier length */
		src_limit = src + KSYM_NAME_LEN;
		src++;
		while (*src && src < src_limit) {
		if (!__btf_name_char_ok(*src, false, dot_ok))
		if (!__btf_name_char_ok(*src, false))
		return false;
		src++;
		}
		@@ -636,17 +635,14 @@ static bool __btf_name_valid(const struct btf *btf, u32 offset, bool dot_ok)
		return !*src;
		}

		/* Only C-style identifier is permitted. This can be relaxed if
		* necessary.
		*/
		static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
		{
		return __btf_name_valid(btf, offset, false);
		return __btf_name_valid(btf, offset);
		}

		static bool btf_name_valid_section(const struct btf *btf, u32 offset)
		{
		return __btf_name_valid(btf, offset, true);
		return __btf_name_valid(btf, offset);
		}

		static const char __btf_name_by_offset(const struct btf btf, u32 offset)
		@@ -3417,7 +3413,7 @@ static s32 btf_var_check_meta(struct btf_verifier_env *env,
		}

		if (!t->name_off \|\|
		!__btf_name_valid(env->btf, t->name_off, true)) {
		!__btf_name_valid(env->btf, t->name_off)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
		}