On 5/31/23 3:09 PM, Yanfei Xu wrote:
On 5/31/2023 11:26 AM, Baolu Lu wrote:
On 5/30/23 5:25 PM, Yanfei Xu wrote:Agree:) It is always better to handle the error than crash kernel.
Checking NULL value of 'table' variable deserves a BUG_ON as the
following code will trigger a crash by dereferencing the NULL
'table' pointer. Crash in advance with BUG_ON to avoid WARN_ON
plus NULL pointer dereferencing can simplify the crash log.
Signed-off-by: Yanfei Xu<yanfei.xu@xxxxxxxxx>
---
drivers/iommu/intel/iommu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index e98f1b122b49..8aa3bfdb7f95 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1944,7 +1944,7 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
if (sm_supported(iommu)) {
unsigned long pds;
- WARN_ON(!table);
+ BUG_ON(!table);
BUG_ON() is not recommended. Perhaps,
if (!table)
-ENODEV;
How about:
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 8096273b034c..7f077e3a4128 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1944,7 +1944,10 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
if (sm_supported(iommu)) {
unsigned long pds;
- WARN_ON(!table);
+ if (WARN_ON(!table)) {
+ ret = -ENODEV;
+ goto out_unlock;
+ }
I'd recommend to remove this line directly. This pointer will be
accessed in the following code, if empty "table" really happens, the
kernel will report a NULL pointer reference warning at the first place.
In the same function, I also saw "WARN_ON(did == 0);". It's unnecessary
as domain_id_iommu() will never return 0. Perhaps we can clean it up as
well.
Best regards,
baolu