strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.
bpf sym names get looked up and compared/cleaned with various string
apis. This suggests they need to be NUL-terminated (strncpy() suggests
this but does not guarantee it).
| static int compare_symbol_name(const char *name, char *namebuf)
| {
| cleanup_symbol_name(namebuf);
| return strcmp(name, namebuf);
| }
| static void cleanup_symbol_name(char *s)
| {
| ...
| res = strstr(s, ".llvm.");
| ...
| }
Use strscpy() as this method guarantees NUL-termination on the
destination buffer.
This patch also replaces two uses of strncpy() used in log.c. These are
simple replacements as postfix has been zero-initialized on the stack
and has source arguments with a size less than the destination's size.
Note that this patch uses the new 2-argument version of strscpy
introduced in Commit e6584c3964f2f ("string: Allow 2-argument
strscpy()").
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@xxxxxxxxxxxxxxx
Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
kernel/bpf/core.c | 4 ++--
kernel/bpf/log.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 696bc55de8e8..8c9078f4549c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -747,7 +747,7 @@ const char *__bpf_address_lookup(unsigned long addr, unsigned long *size,
unsigned long symbol_start = ksym->start;
unsigned long symbol_end = ksym->end;
- strncpy(sym, ksym->name, KSYM_NAME_LEN);
+ strscpy(sym, ksym->name, KSYM_NAME_LEN);
ret = sym;
if (size)
@@ -813,7 +813,7 @@ int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
if (it++ != symnum)
continue;
- strncpy(sym, ksym->name, KSYM_NAME_LEN);
+ strscpy(sym, ksym->name, KSYM_NAME_LEN);
*value = ksym->start;
*type = BPF_SYM_ELF_TYPE;
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 2a243cf37c60..4bd8f17a9f24 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -467,9 +467,9 @@ const char *reg_type_str(struct bpf_verifier_env *env, enum bpf_reg_type type)
if (type & PTR_MAYBE_NULL) {
if (base_type(type) == PTR_TO_BTF_ID)
- strncpy(postfix, "or_null_", 16);
+ strscpy(postfix, "or_null_");
else
- strncpy(postfix, "_or_null", 16);
+ strscpy(postfix, "_or_null");
}
snprintf(prefix, sizeof(prefix), "%s%s%s%s%s%s%s",
---
base-commit: 026e680b0a08a62b1d948e5a8ca78700bfac0e6e
change-id: 20240402-strncpy-kernel-bpf-core-c-4d8297f95e18
Best regards,
--
Justin Stitt <justinstitt@xxxxxxxxxx>
