commit: 767becaac8ccf0a271fc7633fafe635bf8126f3e Author: Mike Frysinger <vapier <AT> gentoo <DOT> org> AuthorDate: Sat Dec 19 06:41:36 2015 +0000 Commit: Mike Frysinger <vapier <AT> gentoo <DOT> org> CommitDate: Sat Dec 19 06:41:36 2015 +0000 URL: https://gitweb.gentoo.org/proj/sandbox.git/commit/?id=767becaa
libsandbox: fix memory alignment Some targets (like sparc32) have higher alignment requirements for 64-bit values than size_t (which is 4 bytes on sparc32). If we happen to return 4 byte aligned memory which is used to hold a 64-bit, we get bus errors. Use the same algorithm that dlmalloc does. URL: https://bugs.gentoo.org/565630 Reported-by: Denis Kaganovich <mahatma <AT> eu.by> Signed-off-by: Mike Frysinger <vapier <AT> gentoo.org> libsandbox/memory.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/libsandbox/memory.c b/libsandbox/memory.c index 5609208..8581128 100644 --- a/libsandbox/memory.c +++ b/libsandbox/memory.c @@ -15,6 +15,9 @@ #include "libsandbox.h" #include "sbutil.h" +/* Pick a value to guarantee alignment requirements. #565630 */ +#define MIN_ALIGN (2 * sizeof(void *)) + /* Well screw me sideways, someone decided to override mmap() #290249 * We probably don't need to include the exact sym version ... */ @@ -35,14 +38,14 @@ static int sb_munmap(void *addr, size_t length) } #define munmap sb_munmap -#define SB_MALLOC_TO_MMAP(ptr) ((void*)(((size_t*)ptr) - 1)) -#define SB_MMAP_TO_MALLOC(ptr) ((void*)(((size_t*)ptr) + 1)) +#define SB_MALLOC_TO_MMAP(ptr) ((void*)((uintptr_t)(ptr) - MIN_ALIGN)) +#define SB_MMAP_TO_MALLOC(ptr) ((void*)((uintptr_t)(ptr) + MIN_ALIGN)) #define SB_MALLOC_TO_SIZE(ptr) (*((size_t*)SB_MALLOC_TO_MMAP(ptr))) void *malloc(size_t size) { size_t *ret; - size += sizeof(size_t); + size += MIN_ALIGN; ret = mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); if (ret == MAP_FAILED) return NULL;
