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([187.15.154.74]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae845aa27esm1970602a91.11.2026.10.29.20.33.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Oct 2026 20:33:17 -0700 (PDT) From: Babanpreet Singh To: Paul Moore Cc: Serge Hallyn , linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Babanpreet Singh , syzbot+ee58b040032d8bed63d9@syzkaller.appspotmail.com, syzbot+557fdc985d6ac3831e14@syzkaller.appspotmail.com Subject: [PATCH] cred: mark the copy in prepare_creds() as a data race Date: Fri, 30 Oct 2026 03:33:08 +0000 Message-ID: <20261030033308.7-1-bbnpreetsingh@gmail.com> X-Mailer: git-send-email 2.47.3 X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit prepare_creds() copies the old cred while other tasks may be changing its refcount. Mark as data race. Reported-by: syzbot+ee58b040032d8bed63d9@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=ee58b040032d8bed63d9 Reported-by: syzbot+557fdc985d6ac3831e14@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=557fdc985d6ac3831e14 Assisted-by: Claude:claude-opus-5-5 Signed-off-by: Babanpreet Singh --- Compile tested with gcc and clang; the KCSAN instrumentation of kernel/cred.o was checked before and after. kernel/cred.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cred.c b/kernel/cred.c index d01df40a9a386..d212db445c138 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -189,7 +189,7 @@ struct cred *prepare_creds(void) kdebug("prepare_creds() alloc %p", new); old = task->cred; - memcpy(new, old, sizeof(struct cred)); + data_race(memcpy(new, old, sizeof(struct cred))); new->non_rcu = 0; atomic_long_set(&new->usage, 1); base-commit: 881f19c2ffbc73f351b257e09c71e6059939b770 -- 2.43.0