Add messages about operations against the NULL pointer, or that result in
a NULL pointer.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/common/ubsan/ubsan.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/xen/common/ubsan/ubsan.c b/xen/common/ubsan/ubsan.c
index 7ebe4bfc14dc..20aa0cb598e1 100644
--- a/xen/common/ubsan/ubsan.c
+++ b/xen/common/ubsan/ubsan.c
@@ -517,9 +517,18 @@ void __ubsan_handle_pointer_overflow(struct pointer_overflow_data *data,
 
 	ubsan_prologue(&data->location, &flags);
 
-	pr_err("pointer operation %s %p to %p\n",
-	       base > result ? "overflowed" : "underflowed",
-	       _p(base), _p(result));
+	if (!base && !result)
+		pr_err("applying zero offset to null pointer\n");
+	else if (!base && result)
+		pr_err("applying non-zero offset %p to null pointer\n",
+			_p(result));
+	else if (base && !result)
+		pr_err("applying non-zero offset to non-null pointer %p produced null pointer\n",
+			_p(base));
+	else
+		pr_err("pointer operation %s %p to %p\n",
+			base > result ? "overflowed" : "underflowed",
+			_p(base), _p(result));
 
 	ubsan_epilogue(&flags);
 }
-- 
2.48.1

On 13/03/2025 3:30 pm, Roger Pau Monne wrote:
> Add messages about operations against the NULL pointer, or that result in
> a NULL pointer.
>
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>