linux-kernel - [PATCH] dma-buf: Replace strlcpy() with strscpy()

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Message-Id: <20231116191409.work.634-kees@kernel.org>
Date:   Thu, 16 Nov 2023 11:14:10 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Sumit Semwal <sumit.semwal@...aro.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Christian König <christian.koenig@....com>,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH] dma-buf: 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].
Additionally, it returns the size of the source string, not the
resulting size of the destination string. In an effort to remove strlcpy()
completely[2], replace strlcpy() here with strscpy().

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1]
Link: https://github.com/KSPP/linux/issues/89 [2]
Cc: Sumit Semwal <sumit.semwal@...aro.org>
Cc: "Christian König" <christian.koenig@....com>
Cc: Azeem Shaikh <azeemshaikh38@...il.com>
Cc: linux-media@...r.kernel.org
Cc: dri-devel@...ts.freedesktop.org
Cc: linaro-mm-sig@...ts.linaro.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/dma-buf/dma-buf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 21916bba77d5..8fe5aa67b167 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -46,12 +46,12 @@ static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
 {
 	struct dma_buf *dmabuf;
 	char name[DMA_BUF_NAME_LEN];
-	size_t ret = 0;
+	ssize_t ret = 0;
 
 	dmabuf = dentry->d_fsdata;
 	spin_lock(&dmabuf->name_lock);
 	if (dmabuf->name)
-		ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
+		ret = strscpy(name, dmabuf->name, sizeof(name));
 	spin_unlock(&dmabuf->name_lock);
 
 	return dynamic_dname(buffer, buflen, "/%s:%s",
-- 
2.34.1