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cpuinfo: Check for overflow in SIMD allocation

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If the size to be allocated is very large and untrusted, then adding
the padding etc. might be enough to cause unsigned overflow, after
which a very small amount of memory will be allocated.

Signed-off-by: Simon McVittie <smcv@collabora.com>
This commit is contained in:
Simon McVittie 2022-05-09 14:58:51 +01:00 committed by Sam Lantinga
parent cf1daafa3f
commit 2a7948016a
1 changed files with 18 additions and 4 deletions
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22
src/cpuinfo/SDL_cpuinfo.c
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@ -1059,9 +1059,17 @@ SDL_SIMDAlloc(const size_t len)
{
const size_t alignment = SDL_SIMDGetAlignment();
const size_t padding = (alignment - (len % alignment)) % alignment;
const size_t padded = len + padding;
Uint8 *retval = NULL;
Uint8 *ptr = (Uint8 *) SDL_malloc(padded + alignment + sizeof (void *));
Uint8 *ptr;
size_t to_allocate;
/* alignment + padding + sizeof (void *) is bounded (a few hundred
* bytes max), so no need to check for overflow within that argument */
if (SDL_size_add_overflow(len, alignment + padding + sizeof (void *), &to_allocate)) {
return NULL;
}
ptr = (Uint8 *) SDL_malloc(to_allocate);
if (ptr) {
/* store the actual allocated pointer right before our aligned pointer. */
retval = ptr + sizeof (void *);
@ -1076,11 +1084,17 @@ SDL_SIMDRealloc(void *mem, const size_t len)
{
const size_t alignment = SDL_SIMDGetAlignment();
const size_t padding = (alignment - (len % alignment)) % alignment;
const size_t padded = len + padding;
Uint8 *retval = (Uint8*) mem;
void *oldmem = mem;
size_t memdiff = 0, ptrdiff;
Uint8 *ptr;
size_t to_allocate;
/* alignment + padding + sizeof (void *) is bounded (a few hundred
* bytes max), so no need to check for overflow within that argument */
if (SDL_size_add_overflow(len, alignment + padding + sizeof (void *), &to_allocate)) {
return NULL;
}
if (mem) {
void **realptr = (void **) mem;
@ -1091,7 +1105,7 @@ SDL_SIMDRealloc(void *mem, const size_t len)
memdiff = ((size_t) oldmem) - ((size_t) mem);
}
ptr = (Uint8 *) SDL_realloc(mem, padded + alignment + sizeof (void *));
ptr = (Uint8 *) SDL_realloc(mem, to_allocate);
if (ptr == NULL) {
return NULL; /* Out of memory, bail! */