https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104262
Bug ID: 104262
Summary: -fsanitize=address false alarm with aligned_alloc
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: eggert at cs dot ucla.edu
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, marxin at
gcc dot gnu.org
Target Milestone: ---
Created attachment 52304
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52304&action=edit
Patch for -fsanitize=address aligned_alloc bug
The following program (adapted from an experimental version of GNU Coreutils)
strictly conforms to C11 and shows a useful pattern of allocating a struct with
a flexible array member:
#include <stdalign.h>
#include <stddef.h>
#include <stdlib.h>
struct namelist
{
struct namelist *next;
char name[];
} *p;
int
main (void)
{
p = aligned_alloc (alignof (struct namelist),
offsetof (struct namelist, name) + 3);
if (!p)
return 1;
p->next = 0;
p->name[0] = 'a';
p->name[1] = 'b';
p->name[2] = 0;
return 0;
}
However, when I compile it with gcc 11.2.1 20211203 (Red Hat 11.2.1-7) using
the command 'gcc -fsanitize=address' it crashes, with the following diagnostic:
=================================================================
==6049==ERROR: AddressSanitizer: invalid alignment requested in aligned_alloc:
8, alignment must be a power of two and the requested size 0xb must be a
multiple of alignment (thread T0)
#0 0x7fbf0f10b32f in aligned_alloc (/lib64/libasan.so.6+0xaf32f)
#1 0x401198 in main (/home/eggert/junk/a.out+0x401198)
#2 0x7fbf0ee7f55f in __libc_start_call_main
../sysdeps/nptl/libc_start_call_main.h:58
==6049==HINT: if you don't care about these errors you may set
allocator_may_return_null=1
SUMMARY: AddressSanitizer: invalid-aligned-alloc-alignment
(/lib64/libasan.so.6+0xaf32f) in aligned_alloc
==6049==ABORTING
Proposed (untested) patch attached. Unfortunately I'm not plugged into the
relationship between GCC and Clang compiler-rt, so I don't know how you manage
patches to this part of the GCC source code or do testcases or cleanups etc.
However, please install something like this patch into GCC's copy of the
AddressSanitizer library. Thanks.
