2ad9cf52eb
in case of mmap-obtained chunks, end points past the end of the mapping and reading it may fault. since the value is not needed until after the conditional, move the access to prevent invalid reads.
52 lines
1.1 KiB
C
52 lines
1.1 KiB
C
#include <stdlib.h>
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#include <stdint.h>
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#include <errno.h>
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/* This function should work with most dlmalloc-like chunk bookkeeping
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* systems, but it's only guaranteed to work with the native implementation
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* used in this library. */
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void *aligned_alloc(size_t align, size_t len)
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{
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unsigned char *mem, *new, *end;
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size_t header, footer;
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if ((align & -align & -sizeof(void *)) != align) {
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errno = EINVAL;
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return NULL;
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}
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if (len > SIZE_MAX - align) {
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errno = ENOMEM;
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return NULL;
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}
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if (align <= 4*sizeof(size_t)) {
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if (!(mem = malloc(len)))
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return NULL;
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return mem;
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}
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if (!(mem = malloc(len + align-1)))
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return NULL;
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header = ((size_t *)mem)[-1];
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new = (void *)((uintptr_t)mem + align-1 & -align);
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if (!(header & 7)) {
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((size_t *)new)[-2] = ((size_t *)mem)[-2] + (new-mem);
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((size_t *)new)[-1] = ((size_t *)mem)[-1] - (new-mem);
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return new;
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}
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end = mem + (header & -8);
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footer = ((size_t *)end)[-2];
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((size_t *)mem)[-1] = header&7 | new-mem;
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((size_t *)new)[-2] = footer&7 | new-mem;
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((size_t *)new)[-1] = header&7 | end-new;
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((size_t *)end)[-2] = footer&7 | end-new;
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if (new != mem) free(mem);
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return new;
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}
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