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From:   Romain Perier <romain.perier@gmail.com>
To:     Kees Cook <keescook@chromium.org>,
        kernel-hardening@lists.openwall.com,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>
Cc:     Romain Perier <romain.perier@gmail.com>,
        linux-kernel@vger.kernel.org
Subject: [PATCH 16/20] tracing/probe: Manual replacement of the deprecated strlcpy() with return values
Date:   Mon, 22 Feb 2021 16:12:27 +0100
Message-Id: <20210222151231.22572-17-romain.perier@gmail.com>
In-Reply-To: <20210222151231.22572-1-romain.perier@gmail.com>
References: <20210222151231.22572-1-romain.perier@gmail.com>
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The strlcpy() reads the entire source buffer first, it is dangerous if
the source buffer lenght is unbounded or possibility non NULL-terminated.
It can lead to linear read overflows, crashes, etc...

As recommended in the deprecated interfaces [1], it should be replaced
by strscpy.

This commit replaces all calls to strlcpy that handle the return values
by the corresponding strscpy calls with new handling of the return
values (as it is quite different between the two functions).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy

Signed-off-by: Romain Perier <romain.perier@gmail.com>
---
 kernel/trace/trace_uprobe.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 3cf7128e1ad3..f9583afdb735 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -154,12 +154,11 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
 	u8 *dst = get_loc_data(dest, base);
 	void __user *src = (void __force __user *) addr;
 
-	if (unlikely(!maxlen))
-		return -ENOMEM;
-
-	if (addr == FETCH_TOKEN_COMM)
-		ret = strlcpy(dst, current->comm, maxlen);
-	else
+	if (addr == FETCH_TOKEN_COMM) {
+		ret = strscpy(dst, current->comm, maxlen);
+		if (ret == -E2BIG)
+			return -ENOMEM;
+	} else
 		ret = strncpy_from_user(dst, src, maxlen);
 	if (ret >= 0) {
 		if (ret == maxlen)