https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63802
Bug ID: 63802
Summary: UBSan doesn't catch misaligned access if address is
16-bytes (or more) aligned
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: ryabinin.a.a at gmail dot com
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org,
mpolacek at gcc dot gnu.org
Created attachment 33929
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33929&action=edit
Repro case
Let's say we have struct that requires 64-bytes alignment.
struct test_struct {
unsigned long a;
int b;
} __attribute__((__aligned__(64)));
UBSan will not catch misaligned access if address of such struct is 16 bytes
aligned.
If address is not aligned to 16 bytes, UBSan will catch it, but alignment in
report is wrong (16 instead of 64):
misaligned_test.c:14:80: runtime error: member access within misaligned address
0x0000006011cf for type 'struct test_struct', which requires 16 byte alignment
0x0000006011cf: note: pointer points here
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00
^
