Re: [PATCH] lib: logic_pio: Fix potential NULL pointer dereference

From: John Garry
Date: Wed Apr 04 2018 - 04:54:20 EST


On 03/04/2018 22:15, Gustavo A. R. Silva wrote:
new_range is being dereferenced before it is null checked, hence
there is a potential null pointer dereference.

Fix this by moving the pointer dereference after new_range has
been properly null checked.


Hi Gustavo,

In fact we expect new_range to never be NULL. But, if we're going to check, then better make sure the check is correct...

Thanks,
John

Addresses-Coverity-ID: 1466163 ("Dereference before null check")
Fixes: 0a7198426259 ("lib: Add generic PIO mapping method")
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>

Reviewed-by: John Garry <john.garry@xxxxxxxxxx>

---
lib/logic_pio.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/logic_pio.c b/lib/logic_pio.c
index 29cedea..30dfdce 100644
--- a/lib/logic_pio.c
+++ b/lib/logic_pio.c
@@ -33,8 +33,8 @@ static DEFINE_MUTEX(io_range_mutex);
int logic_pio_register_range(struct logic_pio_hwaddr *new_range)
{
struct logic_pio_hwaddr *range;
- resource_size_t start = new_range->hw_start;
- resource_size_t end = new_range->hw_start + new_range->size;
+ resource_size_t start;
+ resource_size_t end;
resource_size_t mmio_sz = 0;
resource_size_t iio_sz = MMIO_UPPER_LIMIT;
int ret = 0;
@@ -42,6 +42,9 @@ int logic_pio_register_range(struct logic_pio_hwaddr *new_range)
if (!new_range || !new_range->fwnode || !new_range->size)
return -EINVAL;

+ start = new_range->hw_start;
+ end = new_range->hw_start + new_range->size;
+
mutex_lock(&io_range_mutex);
list_for_each_entry_rcu(range, &io_range_list, list) {
if (range->fwnode == new_range->fwnode) {