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Message-ID: <20230803-security-tomoyo-v1-1-c53a17908d2f@google.com>
Date: Thu, 03 Aug 2023 21:33:44 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Kentaro Takeda <takedakn@...data.co.jp>,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>
Cc: linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
linux-hardening@...r.kernel.org,
Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] tomoyo: refactor deprecated strncpy
`strncpy` is deprecated for use on NUL-terminated destination strings [1].
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`!
It should be noted that the destination buffer is zero-initialized and
had a max length of `sizeof(dest) - 1`. There is likely _not_ a bug
present in the current implementation. However, by switching to
`strscpy` we get the benefit of no longer needing the `- 1`'s from the
string copy invocations on top of `strscpy` being a safer interface all
together.
[1]: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
[2]: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
security/tomoyo/domain.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/security/tomoyo/domain.c b/security/tomoyo/domain.c
index ac20c0bdff9d..90b53500a236 100644
--- a/security/tomoyo/domain.c
+++ b/security/tomoyo/domain.c
@@ -784,13 +784,12 @@ int tomoyo_find_next_domain(struct linux_binprm *bprm)
if (!strcmp(domainname, "parent")) {
char *cp;
- strncpy(ee->tmp, old_domain->domainname->name,
- TOMOYO_EXEC_TMPSIZE - 1);
+ strscpy(ee->tmp, old_domain->domainname->name, TOMOYO_EXEC_TMPSIZE);
cp = strrchr(ee->tmp, ' ');
if (cp)
*cp = '\0';
} else if (*domainname == '<')
- strncpy(ee->tmp, domainname, TOMOYO_EXEC_TMPSIZE - 1);
+ strscpy(ee->tmp, domainname, TOMOYO_EXEC_TMPSIZE);
else
snprintf(ee->tmp, TOMOYO_EXEC_TMPSIZE - 1, "%s %s",
old_domain->domainname->name, domainname);
---
base-commit: 5d0c230f1de8c7515b6567d9afba1f196fb4e2f4
change-id: 20230803-security-tomoyo-7d58f53d35a6
Best regards,
--
Justin Stitt <justinstitt@...gle.com>
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