在 2024/09/18 0:29, Zhu Yanjun 写道:
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.
Because "unsigned long" on 32-bits architectures is 32 bit, so solution
1 is to change the type "unsigned long" to u64, and the diff is as below:
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 2f0431e42c49..27a453b3094d 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 = (u64)g_gb * 1024;
dev->completion_nsec = g_completion_nsec;
dev->submit_queues = g_submit_queues;
dev->prev_submit_queues = g_submit_queues;
diff --git a/drivers/block/null_blk/null_blk.h
b/drivers/block/null_blk/null_blk.h
index a7bb32f73ec3..e30c011909ad 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -74,7 +74,7 @@ struct nullb_device {
bool need_zone_res_mgmt;
spinlock_t zone_res_lock;
- unsigned long size; /* device size in MB */
+ u64 size; /* device size in MB */
There is more, g_gb is GB, dev->size is MB, and dev->size will be used
later for inode size in bytes, and bdev size in sectors.
The max inode size is LONG_MAX, this is still more than UINT_MAX GB, so
it's right that set the device size by module params won't overflow.
However, take a look at setting the size through configfs, the max value
is ULONG_MAX MB, this will still overflow.
Thanks,
Kuai
unsigned long completion_nsec; /* time in ns to complete a
request */
unsigned long cache_size; /* disk cache size in MB */
unsigned long zone_size; /* zone size in MB if device is zoned */
I just built it and did not make tests.
Zhu Yanjun
dev->completion_nsec = g_completion_nsec;
dev->submit_queues = g_submit_queues;
dev->prev_submit_queues = g_submit_queues;
.
