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From: Baokun Li <>
To: <>, <>,
	<>, <>,
Cc: <>, <>,
	Hulk Robot <>
Subject: [PATCH -next v2] nbd: add the check to prevent overflow in __nbd_ioctl()
Date: Mon, 2 Aug 2021 15:56:15 +0800	[thread overview]
Message-ID: <> (raw)

If user specify a large enough value of NBD blocks option, it may trigger
signed integer overflow which may lead to nbd->config->bytesize becomes a
large or small value, zero in particular.

UBSAN: Undefined behaviour in drivers/block/nbd.c:325:31
signed integer overflow:
1024 * 4611686155866341414 cannot be represented in type 'long long int'
Call trace:
 handle_overflow+0x188/0x1dc lib/ubsan.c:192
 __ubsan_handle_mul_overflow+0x34/0x44 lib/ubsan.c:213
 nbd_size_set drivers/block/nbd.c:325 [inline]
 __nbd_ioctl drivers/block/nbd.c:1342 [inline]
 nbd_ioctl+0x998/0xa10 drivers/block/nbd.c:1395
 __blkdev_driver_ioctl block/ioctl.c:311 [inline]

Although it is not a big deal, still silence the UBSAN by limit
the input value.

Reported-by: Hulk Robot <>
Signed-off-by: Baokun Li <>
	Use check_mul_overflow().

 drivers/block/nbd.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index c38317979f74..9f3e25f74e9b 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1384,6 +1384,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		       unsigned int cmd, unsigned long arg)
 	struct nbd_config *config = nbd->config;
+	loff_t bytesize;
 	switch (cmd) {
@@ -1398,8 +1399,10 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 	case NBD_SET_SIZE:
 		return nbd_set_size(nbd, arg, config->blksize);
-		return nbd_set_size(nbd, arg * config->blksize,
-				    config->blksize);
+		if (unlikely(check_mul_overflow(arg, config->blksize,
+						&bytesize)))
+			return -EINVAL;
+		return nbd_set_size(nbd, bytesize, config->blksize);
 		nbd_set_cmd_timeout(nbd, arg);
 		return 0;

             reply	other threads:[~2021-08-02  7:45 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-02  7:56 Baokun Li [this message]
2021-08-02 10:34 ` kernel test robot
2021-08-02 11:38 ` kernel test robot

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