linux-hardening - [PATCH 2/2] ocfs2: Replace strlcpy with strscpy

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Date:   Wed, 30 Aug 2023 21:54:26 +0000
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     Mark Fasheh <mark@...heh.com>, Joel Becker <jlbec@...lplan.org>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>
Cc:     linux-hardening@...r.kernel.org,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        ocfs2-devel@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Christian Brauner <brauner@...nel.org>,
        Dave Chinner <dchinner@...hat.com>,
        Jeff Layton <jlayton@...nel.org>
Subject: [PATCH 2/2] ocfs2: Replace strlcpy with strscpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

Direct replacement is assumed to be safe here since
it's ok for `kernel_param_ops.get()` to return -errno [3].
This changes the behavior such that instead of silently ignoring the
case when sizeof(@buffer) < DLMFS_CAPABILITIES, we now return error.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89
[3] https://elixir.bootlin.com/linux/v6.5/source/include/linux/moduleparam.h#L52

Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>
---
 fs/ocfs2/dlmfs/dlmfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index 33e529de93b2..b001eccdd2f3 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -80,7 +80,7 @@ static int param_set_dlmfs_capabilities(const char *val,
 static int param_get_dlmfs_capabilities(char *buffer,
 					const struct kernel_param *kp)
 {
-	return strlcpy(buffer, DLMFS_CAPABILITIES,
+	return strscpy(buffer, DLMFS_CAPABILITIES,
 		       strlen(DLMFS_CAPABILITIES) + 1);
 }
 static const struct kernel_param_ops dlmfs_capabilities_ops = {
--
2.42.0.283.g2d96d420d3-goog