linux-hardening - [PATCH v2] fs: ocfs2: Replace strlcpy with sysfs

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Date:   Thu, 31 Aug 2023 19:38:27 +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>,
        Kees Cook <keescook@...omium.org>
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>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v2] fs: ocfs2: Replace strlcpy with sysfs_emit

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 sysfs_emit().

Direct replacement is safe here since its ok for `kernel_param_ops.get()`
to return -errno [3].

[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>
---
v2:
 * Removes patch [1/2] which replaced module_param_call with module_param_cb.
 * Use sysfs_emit instead of strscpy.

v1:
 * https://lore.kernel.org/all/20230830215426.4181755-1-azeemshaikh38@gmail.com/

 fs/ocfs2/dlmfs/dlmfs.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index 81265123ce6c..b38776ba3306 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -80,8 +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,
-		       strlen(DLMFS_CAPABILITIES) + 1);
+	return sysfs_emit(buffer, DLMFS_CAPABILITIES);
 }
 module_param_call(capabilities, param_set_dlmfs_capabilities,
 		  param_get_dlmfs_capabilities, NULL, 0444);
--
2.42.0.283.g2d96d420d3-goog