Messages in this thread | | | Subject | Re: [PATCH] bpf: replace deprecated strncpy with strscpy | From | Daniel Borkmann <> | Date | Wed, 3 Apr 2024 16:55:00 +0200 |
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On 4/3/24 5:06 AM, Ratheesh Kannoth wrote: > On 2024-04-03 at 05:22:50, Justin Stitt (justinstitt@google.com) wrote: >> 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@vger.kernel.org >> Signed-off-by: Justin Stitt <justinstitt@google.com> >> --- >> 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); > You dont have to check return value of strscpy for errors ?
That would be overkill, it can be easily audited that both pointers are of size KSYM_NAME_LEN, as is the count arg.
Thanks, Daniel
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