From: Zhong Jinghua zhongjinghua@huawei.com
[ Upstream commit 55793ea54d77719a071b1ccc05a05056e3b5e009 ]
We tested and found an alarm caused by nbd_ioctl arg without verification. The UBSAN warning calltrace like below:
UBSAN: Undefined behaviour in fs/buffer.c:1709:35 signed integer overflow: -9223372036854775808 - 1 cannot be represented in type 'long long int' CPU: 3 PID: 2523 Comm: syz-executor.0 Not tainted 4.19.90 #1 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x3f0 arch/arm64/kernel/time.c:78 show_stack+0x28/0x38 arch/arm64/kernel/traps.c:158 __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x170/0x1dc lib/dump_stack.c:118 ubsan_epilogue+0x18/0xb4 lib/ubsan.c:161 handle_overflow+0x188/0x1dc lib/ubsan.c:192 __ubsan_handle_sub_overflow+0x34/0x44 lib/ubsan.c:206 __block_write_full_page+0x94c/0xa20 fs/buffer.c:1709 block_write_full_page+0x1f0/0x280 fs/buffer.c:2934 blkdev_writepage+0x34/0x40 fs/block_dev.c:607 __writepage+0x68/0xe8 mm/page-writeback.c:2305 write_cache_pages+0x44c/0xc70 mm/page-writeback.c:2240 generic_writepages+0xdc/0x148 mm/page-writeback.c:2329 blkdev_writepages+0x2c/0x38 fs/block_dev.c:2114 do_writepages+0xd4/0x250 mm/page-writeback.c:2344
The reason for triggering this warning is __block_write_full_page() -> i_size_read(inode) - 1 overflow. inode->i_size is assigned in __nbd_ioctl() -> nbd_set_size() -> bytesize. We think it is necessary to limit the size of arg to prevent errors.
Moreover, __nbd_ioctl() -> nbd_add_socket(), arg will be cast to int. Assuming the value of arg is 0x80000000000000001) (on a 64-bit machine), it will become 1 after the coercion, which will return unexpected results.
Fix it by adding checks to prevent passing in too large numbers.
Signed-off-by: Zhong Jinghua zhongjinghua@huawei.com Reviewed-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Josef Bacik josef@toxicpanda.com Link: https://lore.kernel.org/r/20230206145805.2645671-1-zhongjinghua@huawei.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/block/nbd.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index ade8b839e4458..394355f12d4e0 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -326,6 +326,9 @@ static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize, if (blksize < 512 || blksize > PAGE_SIZE || !is_power_of_2(blksize)) return -EINVAL;
+ if (bytesize < 0) + return -EINVAL; + nbd->config->bytesize = bytesize; nbd->config->blksize_bits = __ffs(blksize);
@@ -1048,6 +1051,9 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg, struct nbd_sock *nsock; int err;
+ /* Arg will be cast to int, check it to avoid overflow */ + if (arg > INT_MAX) + return -EINVAL; sock = nbd_get_socket(nbd, arg, &err); if (!sock) return err;