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

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>

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c b/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
index 2500f5b..881d704 100644 (file)
--- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
@@ -999,12 +999,10 @@ 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';