[PATCH v2 22/53] objtool: Fix reloc hash collision in find_reloc_by_dest_range()

[Josh Poimboeuf]

In find_reloc_by_dest_range(), hash collisions can cause a high-offset
relocation to appear when probing a low-offset hash bucket.

Only return early when the best match found so far genuinely belongs to
the current bucket (its offset is within the bucket's stride range).
Otherwise, continue scanning later buckets which may contain
lower-offset matches.

This ensures the first reloc in the range gets returned.

Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Fixes: 74b873e49d92 ("objtool: Optimize find_rela_by_dest_range()")
Acked-by: Song Liu <song@xxxxxxxxxx>
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 tools/objtool/elf.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 5a20dab683dd..f41280e454ca 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -315,8 +315,9 @@ struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *nam
 	return NULL;
 }
 
+/* If there are multiple matches, return the first one in the range */
 struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,
-				     unsigned long offset, unsigned int len)
+				       unsigned long offset, unsigned int len)
 {
 	struct reloc *reloc, *r = NULL;
 	struct section *rsec;
@@ -338,11 +339,11 @@ struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *se
 					r = reloc;
 			}
 		}
-		if (r)
+		if (r && (reloc_offset(r) & OFFSET_STRIDE_MASK) == o)
 			return r;
 	}
 
-	return NULL;
+	return r;
 }
 
 struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset)
-- 
2.53.0