From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Wed, 17 Nov 2021 10:34:54 +0300
Subject: octeontx2-af: debugfs: don't corrupt user memory
Patch-mainline: v5.16-rc2
Git-commit: a280ef90af01dc133d0a52387e563015686d6294
References: jsc#SLE-24682

The user supplies the "count" value to say how big its read buffer is.
The rvu_dbg_lmtst_map_table_display() function does not take the "count"
into account but instead just copies the whole table, potentially
corrupting the user's data.

Introduce the "ret" variable to store how many bytes we can copy.  Also
I changed the type of "off" to size_t to make using min() simpler.

Fixes: 0daa55d033b0 ("octeontx2-af: cn10k: debugfs for dumping LMTST map table")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20211117073454.GD5237@kili
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c |   17 +++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

--- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
@@ -303,10 +303,11 @@ static ssize_t rvu_dbg_lmtst_map_table_d
 	u64 lmt_addr, val, tbl_base;
 	int pf, vf, num_vfs, hw_vfs;
 	void __iomem *lmt_map_base;
-	int index = 0, off = 0;
-	int bytes_not_copied;
 	int buf_size = 10240;
+	size_t off = 0;
+	int index = 0;
 	char *buf;
+	int ret;
 
 	/* don't allow partial reads */
 	if (*ppos != 0)
@@ -370,15 +371,17 @@ static ssize_t rvu_dbg_lmtst_map_table_d
 	}
 	off +=	scnprintf(&buf[off], buf_size - 1 - off, "\n");
 
-	bytes_not_copied = copy_to_user(buffer, buf, off);
+	ret = min(off, count);
+	if (copy_to_user(buffer, buf, ret))
+		ret = -EFAULT;
 	kfree(buf);
 
 	iounmap(lmt_map_base);
-	if (bytes_not_copied)
-		return -EFAULT;
+	if (ret < 0)
+		return ret;
 
-	*ppos = off;
-	return off;
+	*ppos = ret;
+	return ret;
 }
 
 RVU_DEBUG_FOPS(lmtst_map_table, lmtst_map_table_display, NULL);