[PATCH] libdwfl: Make sure note data is properly aligned.

[PATCH] libdwfl: Make sure note data is properly aligned.

[Mark Wielaard]

In dwfl_segment_report_module the note data might not be properly
aligned. Check that it is before accessing the data directly.
Otherwise convert data so it is properly aligned.

Also fix NOTE_ALIGN4 and NOTE_ALIGN8 to work correctly with long
types.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdwfl/ChangeLog                    | 5 +++++
 libdwfl/dwfl_segment_report_module.c | 5 ++++-
 libelf/ChangeLog                     | 5 +++++
 libelf/libelfP.h                     | 4 ++--
 4 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 8760b1ef..f18a0c45 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,8 @@
+2021-12-16  Mark Wielaard  <mark@klomp.org>
+
+	* dwfl_segment_report_module.c (dwfl_segment_report_module): Check
+	note data is properly aligned.
+
 2021-12-16  Mark Wielaard  <mark@klomp.org>
 
 	* link_map.c (dwfl_link_map_report): Make sure phnum is non-zero.
diff --git a/libdwfl/dwfl_segment_report_module.c b/libdwfl/dwfl_segment_report_module.c
index f323929e..2263e3cc 100644
--- a/libdwfl/dwfl_segment_report_module.c
+++ b/libdwfl/dwfl_segment_report_module.c
@@ -517,7 +517,10 @@ dwfl_segment_report_module (Dwfl *dwfl, int ndx, const char *name,
               assert (sizeof (Elf32_Nhdr) == sizeof (Elf64_Nhdr));
 
               void *notes;
-              if (ei_data == MY_ELFDATA)
+              if (ei_data == MY_ELFDATA
+		  && (uintptr_t) data == (align == 8
+					  ? NOTE_ALIGN8 ((uintptr_t) data)
+					  : NOTE_ALIGN4 ((uintptr_t) data)))
                 notes = data;
               else
                 {
diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index 96059eff..617d97a5 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,8 @@
+2021-12-16  Mark Wielaard  <mark@klomp.org>
+
+	* libelfP.h (NOTE_ALIGN4): And with negative unsigned long.
+	(NOTE_ALIGN8): Likewise.
+
 2021-12-15  Mark Wielaard  <mark@klomp.org>
 
 	* elf_begin.c (get_shnum): Use offsetof to get field of unaligned
diff --git a/libelf/libelfP.h b/libelf/libelfP.h
index fc1aebec..2c6995bb 100644
--- a/libelf/libelfP.h
+++ b/libelf/libelfP.h
@@ -603,10 +603,10 @@ extern void __libelf_reset_rawdata (Elf_Scn *scn, void *buf, size_t size,
 /* Align offset to 4 bytes as needed for note name and descriptor data.
    This is almost always used, except for GNU Property notes, which use
    8 byte padding...  */
-#define NOTE_ALIGN4(n)	(((n) + 3) & -4U)
+#define NOTE_ALIGN4(n)	(((n) + 3) & -4UL)
 
 /* Special note padding rule for GNU Property notes.  */
-#define NOTE_ALIGN8(n)	(((n) + 7) & -8U)
+#define NOTE_ALIGN8(n)	(((n) + 7) & -8UL)
 
 /* Convenience macro.  */
 #define INVALID_NDX(ndx, type, data) \
-- 
2.30.2