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improve padding and error messages

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This commit is contained in:
Daan Leijen 2021-12-10 11:09:19 -08:00
parent ea75c745e1
commit 28893a6c1b
5 changed files with 162 additions and 93 deletions
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20
include/mimalloc-types.h
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@ -60,7 +60,7 @@ terms of the MIT license. A copy of the license can be found in the file
#define MI_PADDING 1
#endif
#if !defined(MI_DEBUG_TRACE) // store stack trace at each allocation
#if !defined(MI_DEBUG_TRACE) // store stack trace at each allocation
#define MI_DEBUG_TRACE MI_DEBUG
#endif
@ -79,6 +79,7 @@ terms of the MIT license. A copy of the license can be found in the file
// Encoded free lists allow detection of corrupted free lists
// and can detect buffer overflows, modify after free, and double `free`s.
// (It must be enabled if MI_PADDING is enabled as the same mechanism is used to encode the canary.)
#if (MI_SECURE>=3 || MI_DEBUG>=1 || MI_PADDING > 0)
#define MI_ENCODE_FREELIST 1
#endif
@ -367,11 +368,20 @@ typedef struct mi_random_cxt_s {
} mi_random_ctx_t;
// In debug mode there is a padding structure at the end of the blocks to check for buffer overflows
// If MI_PADDING is enabled, there is a padding structure at the end of the blocks to check for buffer overflows
// The full layout is of a block becomes:
//
// |--- data ---------|--- fill ----------|--- struct padding_s -----------------------------------------|
// |.. actual data .. | .. delta bytes .. | canary_lo | .. extra .. | canary | delta | .. stack trace .. |
//
// where the delta bytes are used to align the padding structure and to detect byte precise overflow.
// The `canary` is used to see if `delta` and `strace` are not corrupted, while `canary_lo` can
// detect overflow into the `extra` padding (where the stack trace could remain valid)
#if (MI_PADDING)
typedef struct mi_padding_s {
#if MI_PADDING_EXTRA > 0
uint32_t canary_lo;
uint32_t canary_lo; // extra canary to detect initial overflow
uint8_t extra[MI_PADDING_EXTRA];
#endif
uint32_t canary; // encoded block value to check validity of the delat (in case of overflow)
@ -380,7 +390,7 @@ typedef struct mi_padding_s {
void* strace[MI_DEBUG_TRACE_LEN]; // stack trace at allocation time
#endif
} mi_padding_t;
#define MI_PADDING_MINSIZE (8) // 2*sizeof(uint32_t)
#define MI_PADDING_MINSIZE (8) // 2*sizeof(uint32_t)
#define MI_PADDING_SIZE (sizeof(mi_padding_t))
#else
#define MI_PADDING_MINSIZE (0)
@ -388,6 +398,8 @@ typedef struct mi_padding_s {
#endif
// add 2 more for minimal padding (MI_PADDING && !MI_DEBUG_TRACE && MI_PADDING_EXTRA==0)
// since this is used in secure mode, we optimize this case by allowing
// `heap_malloc_small` to also work with `MI_WSMALL_SIZE_MAX + MI_PADDING_MINSIZE` sizes.
// see `init.c` where all are initialized with an empty page and the check at `heap_malloc_small`.
#define MI_PAGES_DIRECT (MI_SMALL_WSIZE_MAX + 1 + 2)