From: Florent Revest <revest@xxxxxxxxxxxx>
[ Upstream commit 9724160b3942b0a967b91a59f81da5593f28b8ba ]
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: 1dc92851849c ("bpf: kernel side support for BTF Var and DataSec")
Signed-off-by: Florent Revest <revest@xxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Yonghong Song <yhs@xxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20230615145607.3469985-1-revest@xxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/bpf/btf.c | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 46bce5577fb48..3cc3232f8c334 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -735,13 +735,12 @@ static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
return 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;
}
@@ -758,20 +757,20 @@ static const char *btf_str_by_offset(const struct btf *btf, u32 offset)
return NULL;
}
-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_str_by_offset(btf, 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++;
}
@@ -779,17 +778,14 @@ 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)
@@ -4450,7 +4446,7 @@ 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;
}
--
2.39.2
