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 2500f5ba4f5a42b43ee5de8d64d7f06fb70cdd87..881d704644fbee77cf5c9f7137d539463c08c2dd 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';