On Mon, Jul 15, 2024 at 04:28:15PM +1000, Michael Ellerman wrote:

Ma Ke [off-list ref] writes:

quoted

In read_handle(), of_get_address() may return NULL if getting address and
size of the node failed. When of_read_number() uses prop to handle
conversions between different byte orders, it could lead to a null pointer
dereference. Add NULL check to fix potential issue.

Found by static analysis.

Cc: stable@vger.kernel.org
Fixes: 14baf4d9c739 ("cxl: Add guest-specific code")
Signed-off-by: Ma Ke <redacted>

The bug is real and the fix looks okay to me. I'm surprised that Smatch doesn't
print a warning about "size" being uninitialized.  I must not have it enabled
in the .configs that I test.  But I also wouldn't have reported that because
it's from 2016 so it's too old.

quoted

---
Changes in v4:
- modified vulnerability description according to suggestions, making the 
process of static analysis of vulnerabilities clearer. No active research 
on developer behavior.
Changes in v3:
- fixed up the changelog text as suggestions.
Changes in v2:
- added an explanation of how the potential vulnerability was discovered,
but not meet the description specification requirements.
---
 drivers/misc/cxl/of.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/cxl/of.c b/drivers/misc/cxl/of.c
index bcc005dff1c0..d8dbb3723951 100644
--- a/drivers/misc/cxl/of.c
+++ b/drivers/misc/cxl/of.c

@@ -58,7 +58,7 @@ static int read_handle(struct device_node *np, u64 *handle)
 
 	/* Get address and size of the node */
 	prop = of_get_address(np, 0, &size, NULL);
-	if (size)
+	if (!prop || size)
 		return -EINVAL;
 
 	/* Helper to read a big number; size is in cells (not bytes) */

If you expand the context this could just use of_property_read_reg(),
something like below.

You're a domain expert so I trust you, but as a static checker person, there is
no way I'd feel comfortable sending a patch like that...  It's way too
complicated and I wouldn't be able to test it.  If this were my patch I would
ask you to handle send that patch and give me Reported-by credit.

regards,
dan carpenter