linux-kernel - [PATCH] gve: Fix a possible invalid memory access

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Message-Id: <fb712f802228ab4319891983164bf45e90d529e7.1635076200.git.christophe.jaillet@wanadoo.fr>
Date:   Sun, 24 Oct 2021 13:52:37 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     jeroendb@...gle.com, csully@...gle.com, awogbemila@...gle.com,
        davem@...emloft.net, kuba@...nel.org, willemb@...gle.com,
        bcf@...gle.com, gustavoars@...nel.org, edumazet@...gle.com,
        jfraker@...gle.com, yangchun@...gle.com, xliutaox@...gle.com,
        sagis@...gle.com, lrizzo@...gle.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] gve: Fix a possible invalid memory access

It is spurious to allocate a bitmap for 'num_qpls' bits and record the
size of this bitmap with another value.

'qpl_map_size' is used in 'drivers/net/ethernet/google/gve/gve.h' with
'find_[first|next]_zero_bit()'.
So, it looks that memory after the allocated 'qpl_id_map' could be
scanned.

Remove the '* BITS_PER_BYTE' to have allocation and length be the same.

Fixes: f5cedc84a30d ("gve: Add transmit and receive support")
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
This patch is completely speculative and un-tested!
You'll be warned.
---
 drivers/net/ethernet/google/gve/gve_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index 7647cd05b1d2..19fe9e9b62f5 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -866,7 +866,7 @@ static int gve_alloc_qpls(struct gve_priv *priv)
 	}
 
 	priv->qpl_cfg.qpl_map_size = BITS_TO_LONGS(num_qpls) *
-				     sizeof(unsigned long) * BITS_PER_BYTE;
+				     sizeof(unsigned long);
 	priv->qpl_cfg.qpl_id_map = kvcalloc(BITS_TO_LONGS(num_qpls),
 					    sizeof(unsigned long), GFP_KERNEL);
 	if (!priv->qpl_cfg.qpl_id_map) {
-- 
2.30.2