linux-kernel - [PATCH v3] vfio: Clear the caps->buf to NULL after free

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Message-Id: <20220629022948.55608-1-schspa@gmail.com>
Date:   Wed, 29 Jun 2022 10:29:48 +0800
From:   Schspa Shi <schspa@...il.com>
To:     alex.williamson@...hat.com, cohuck@...hat.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Schspa Shi <schspa@...il.com>
Subject: [PATCH v3] vfio: Clear the caps->buf to NULL after free

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>

-- 

Changelog:
v1 -> v2:
        - Remove incorrect double free report in commit message.
v2 -> v3:
        - Update commit comment as Alex advised.
---
 drivers/vfio/vfio.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 61e71c1154be..a0fb93866f61 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1812,6 +1812,7 @@ 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);
 	}
-- 
2.29.0