[PATCH 5.15 020/177] vduse: fix memory corruption in vduse_dev_ioctl()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

commit ff9f9c6e74848170fcb45c8403c80d661484c8c9 upstream.

The "config.offset" comes from the user.  There needs to a check to
prevent it being out of bounds.  The "config.offset" and
"dev->config_size" variables are both type u32.  So if the offset if
out of bounds then the "dev->config_size - config.offset" subtraction
results in a very high u32 value.  The out of bounds offset can result
in memory corruption.

Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211208103307.GA3778@kili
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/vdpa/vdpa_user/vduse_dev.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -975,7 +975,8 @@ static long vduse_dev_ioctl(struct file
 			break;
 
 		ret = -EINVAL;
-		if (config.length == 0 ||
+		if (config.offset > dev->config_size ||
+		    config.length == 0 ||
 		    config.length > dev->config_size - config.offset)
 			break;