[xen staging] xen/ubsan: expand pointer overflow message printing

[patchbot@xxxxxxx]

commit 53ec18fa8f590ea6ad4792a0b126013dd39a25ee
Author:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
AuthorDate: Thu Mar 13 12:02:50 2025 +0100
Commit:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
CommitDate: Mon Mar 17 13:33:29 2025 +0100

    xen/ubsan: expand pointer overflow message printing
    
    Add messages about operations against the NULL pointer, or that result in
    a NULL pointer.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 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 7ebe4bfc14..20aa0cb598 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);
 }
--
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