Messages in this thread Patch in this message | | | Date | Fri, 11 Aug 2023 16:33:51 +0000 | Subject | [PATCH v2] arm64/sysreg: refactor deprecated strncpy | From | Justin Stitt <> |
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`strncpy` is deprecated for use on NUL-terminated destination strings [1]. Which seems to be the case here due to the forceful setting of `buf`'s tail to 0.
A suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on its destination buffer argument which is _not_ the case for `strncpy`!
In this case, we can simplify the logic and also check for any silent truncation by using `strscpy`'s return value.
This should have no functional change and yet uses a more robust and less ambiguous interface whilst reducing code complexity.
Link: 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 Suggested-by: Kees Cook <keescook@chromium.org> Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt <justinstitt@google.com> --- Changes in v2: - Utilize return value from strscpy and check for truncation (thanks Kees) - Link to v1: https://lore.kernel.org/r/20230810-strncpy-arch-arm64-v1-1-f67f3685cd64@google.com --- For reference, see a part of `strscpy`'s implementation here:
| /* Hit buffer length without finding a NUL; force NUL-termination. */ | if (res) | dest[res-1] = '\0';
Note: compile tested --- arch/arm64/kernel/idreg-override.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c index 2fe2491b692c..aee12c75b738 100644 --- a/arch/arm64/kernel/idreg-override.c +++ b/arch/arm64/kernel/idreg-override.c @@ -262,9 +262,9 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) if (!len) return; - len = min(len, ARRAY_SIZE(buf) - 1); - strncpy(buf, cmdline, len); - buf[len] = 0; + len = strscpy(buf, cmdline, ARRAY_SIZE(buf)); + if (len == -E2BIG) + len = ARRAY_SIZE(buf) - 1; if (strcmp(buf, "--") == 0) return; --- base-commit: 52a93d39b17dc7eb98b6aa3edb93943248e03b2f change-id: 20230810-strncpy-arch-arm64-1f3d328bd9b8 Best regards, -- Justin Stitt <justinstitt@google.com>
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