linux-kernel - [PATCH AUTOSEL 4.9 2/8] vfio: Clear the caps->buf to NULL after free

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Message-Id: <20220814163041.2399552-2-sashal@kernel.org>
Date:   Sun, 14 Aug 2022 12:30:35 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Schspa Shi <schspa@...il.com>, Cornelia Huck <cohuck@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Sasha Levin <sashal@...nel.org>, kvm@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 2/8] vfio: Clear the caps->buf to NULL after free

From: Schspa Shi <schspa@...il.com>

[ Upstream commit 6641085e8d7b3f061911517f79a2a15a0a21b97b ]

On buffer resize failure, vfio_info_cap_add() will free the buffer,
report zero for the size, and return -ENOMEM.  As additional
hardening, also clear the buffer pointer to prevent any chance of a
double free.

Signed-off-by: Schspa Shi <schspa@...il.com>
Reviewed-by: Cornelia Huck <cohuck@...hat.com>
Link: https://lore.kernel.org/r/20220629022948.55608-1-schspa@gmail.com
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/vfio/vfio.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 881fc3a55edc..5798965f42b5 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1793,6 +1793,7 @@ struct vfio_info_cap_header *vfio_info_cap_add(struct vfio_info_cap *caps,
 	buf = krealloc(caps->buf, caps->size + size, GFP_KERNEL);
 	if (!buf) {
 		kfree(caps->buf);
+		caps->buf = NULL;
 		caps->size = 0;
 		return ERR_PTR(-ENOMEM);
 	}
-- 
2.35.1