octeontx2-af: avoid off-by-one read from userspace

[ Upstream commit f299ee709fb45036454ca11e90cb2810fe771878 ]

We try to access count + 1 byte from userspace with memdup_user(buffer,
count + 1). However, the userspace only provides buffer of count bytes and
only these count bytes are verified to be okay to access. To ensure the
copied buffer is NUL terminated, we use memdup_user_nul instead.

Fixes: 3a2eb515d136 ("octeontx2-af: Fix an off by one in rvu_dbg_qsize_write()")
Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
Link: https://lore.kernel.org/r/20240424-fix-oob-read-v2-6-f1f1b53a10f4@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c b/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
index 5205796859f6cb0116ccb59ba6bfa9c378d570e8..d212bab3ddbae5e286c9fe0f410ebb7695922af0 100644 (file)
--- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
@@ -420,12 +420,10 @@ static ssize_t rvu_dbg_qsize_write(struct file *filp,
        u16 pcifunc;
        int ret, lf;
 
-       cmd_buf = memdup_user(buffer, count + 1);
+       cmd_buf = memdup_user_nul(buffer, count);
        if (IS_ERR(cmd_buf))
                return -ENOMEM;
 
-       cmd_buf[count] = '\0';
-
        cmd_buf_tmp = strchr(cmd_buf, '\n');
        if (cmd_buf_tmp) {
                *cmd_buf_tmp = '\0';