在 2024/9/17 15:24, Damien Le Moal 写道:
On 2024/09/17 16:21, Damien Le Moal wrote:
On 2024/09/17 16:07, Aleksandr Mishin wrote:
In null_alloc_dev() device size is a subject to overflow because 'g_gb'
(which is module parameter, may have any value and is not validated
anywhere) is not cast to a larger data type before performing arithmetic.
Cast 'g_gb' to unsigned long to prevent overflow.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Fixes: 2984c8684f96 ("nullb: factor disk parameters")
Signed-off-by: Aleksandr Mishin <amishin@xxxxxxxxxx>
---
drivers/block/null_blk/main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 2f0431e42c49..5edbf9c0aceb 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -762,7 +762,7 @@ static struct nullb_device *null_alloc_dev(void)
return NULL;
}
- dev->size = g_gb * 1024;
+ dev->size = (unsigned long)g_gb * 1024;
This still does not prevent overflows... So what about doing a proper check ?
This still does not prevent overflows on 32-bits architectures.
The max value of "unsigned long" is 2^64 - 1 while the max value of int
is 2^31 -1.
(2^64 - 1) / (2^31-1) is about 2^33 while 1024 is 2^10.
2^33 is greater than 2^10.
So in the above, it seems that it is difficult to overflow.
If I am missing something, please let me know.
Thanks,
Zhu Yanjun
dev->completion_nsec = g_completion_nsec;
dev->submit_queues = g_submit_queues;
dev->prev_submit_queues = g_submit_queues;
--
Best Regards,
Yanjun.Zhu
