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https://github.com/Dasharo/systemd.git
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a88f9dbae2
When fuzzing, the following happens: - we parse 'data' and produce an argv array, - one of the items in argv is assigned to arg_host, - the argv array is subsequently freed by strv_freep(), and arg_host has a dangling symlink. In normal use, argv is static, so arg_host can never become a dangling pointer. In fuzz-systemctl-parse-argv, if we repeatedly parse the same array, we have some dangling pointers while we're in the middle of parsing. If we parse the same array a second time, at the end all the dangling pointers will have been replaced again. But for a short time, if parsing one of the arguments uses another argument, we would use a dangling pointer. Such a case occurs when we have --host=… --boot-loader-entry=help. The latter calls acquire_bus() which uses arg_host. I'm not particularly happy with making the code more complicated just for fuzzing, but I think it's better to resolve this, even if the issue cannot occur in normal invocations, than to deal with fuzzer reports. Should fix https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=31714.
193 lines
7.9 KiB
C
193 lines
7.9 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#pragma once
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#include <alloca.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <string.h>
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#include "macro.h"
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#if HAS_FEATURE_MEMORY_SANITIZER
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# include <sanitizer/msan_interface.h>
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#endif
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typedef void (*free_func_t)(void *p);
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/* If for some reason more than 4M are allocated on the stack, let's abort immediately. It's better than
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* proceeding and smashing the stack limits. Note that by default RLIMIT_STACK is 8M on Linux. */
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#define ALLOCA_MAX (4U*1024U*1024U)
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#define new(t, n) ((t*) malloc_multiply(sizeof(t), (n)))
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#define new0(t, n) ((t*) calloc((n) ?: 1, sizeof(t)))
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#define newa(t, n) \
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({ \
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size_t _n_ = n; \
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assert(!size_multiply_overflow(sizeof(t), _n_)); \
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assert(sizeof(t)*_n_ <= ALLOCA_MAX); \
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(t*) alloca((sizeof(t)*_n_) ?: 1); \
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})
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#define newa0(t, n) \
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({ \
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size_t _n_ = n; \
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assert(!size_multiply_overflow(sizeof(t), _n_)); \
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assert(sizeof(t)*_n_ <= ALLOCA_MAX); \
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(t*) alloca0((sizeof(t)*_n_) ?: 1); \
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})
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#define newdup(t, p, n) ((t*) memdup_multiply(p, sizeof(t), (n)))
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#define newdup_suffix0(t, p, n) ((t*) memdup_suffix0_multiply(p, sizeof(t), (n)))
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#define malloc0(n) (calloc(1, (n) ?: 1))
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static inline void *mfree(void *memory) {
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free(memory);
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return NULL;
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}
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#define free_and_replace(a, b) \
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({ \
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free(a); \
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(a) = (b); \
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(b) = NULL; \
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0; \
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})
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void* memdup(const void *p, size_t l) _alloc_(2);
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void* memdup_suffix0(const void *p, size_t l); /* We can't use _alloc_() here, since we return a buffer one byte larger than the specified size */
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#define memdupa(p, l) \
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({ \
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void *_q_; \
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size_t _l_ = l; \
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assert(_l_ <= ALLOCA_MAX); \
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_q_ = alloca(_l_ ?: 1); \
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memcpy_safe(_q_, p, _l_); \
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})
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#define memdupa_suffix0(p, l) \
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({ \
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void *_q_; \
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size_t _l_ = l; \
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assert(_l_ <= ALLOCA_MAX); \
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_q_ = alloca(_l_ + 1); \
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((uint8_t*) _q_)[_l_] = 0; \
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memcpy_safe(_q_, p, _l_); \
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})
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static inline void unsetp(void *p) {
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/* A trivial "destructor" that can be used in cases where we want to
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* unset a pointer from a _cleanup_ function. */
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*(void**)p = NULL;
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}
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static inline void freep(void *p) {
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*(void**)p = mfree(*(void**) p);
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}
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#define _cleanup_free_ _cleanup_(freep)
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static inline bool size_multiply_overflow(size_t size, size_t need) {
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return _unlikely_(need != 0 && size > (SIZE_MAX / need));
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}
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_malloc_ _alloc_(1, 2) static inline void *malloc_multiply(size_t size, size_t need) {
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if (size_multiply_overflow(size, need))
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return NULL;
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return malloc(size * need ?: 1);
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}
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#if !HAVE_REALLOCARRAY
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_alloc_(2, 3) static inline void *reallocarray(void *p, size_t need, size_t size) {
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if (size_multiply_overflow(size, need))
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return NULL;
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return realloc(p, size * need ?: 1);
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}
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#endif
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_alloc_(2, 3) static inline void *memdup_multiply(const void *p, size_t size, size_t need) {
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if (size_multiply_overflow(size, need))
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return NULL;
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return memdup(p, size * need);
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}
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/* Note that we can't decorate this function with _alloc_() since the returned memory area is one byte larger
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* than the product of its parameters. */
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static inline void *memdup_suffix0_multiply(const void *p, size_t size, size_t need) {
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if (size_multiply_overflow(size, need))
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return NULL;
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return memdup_suffix0(p, size * need);
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}
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void* greedy_realloc(void **p, size_t need, size_t size);
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void* greedy_realloc0(void **p, size_t need, size_t size);
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#define GREEDY_REALLOC(array, need) \
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greedy_realloc((void**) &(array), (need), sizeof((array)[0]))
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#define GREEDY_REALLOC0(array, need) \
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greedy_realloc0((void**) &(array), (need), sizeof((array)[0]))
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#define alloca0(n) \
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({ \
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char *_new_; \
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size_t _len_ = n; \
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assert(_len_ <= ALLOCA_MAX); \
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_new_ = alloca(_len_ ?: 1); \
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(void *) memset(_new_, 0, _len_); \
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})
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/* It's not clear what alignment glibc/gcc alloca() guarantee, hence provide a guaranteed safe version */
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#define alloca_align(size, align) \
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({ \
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void *_ptr_; \
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size_t _mask_ = (align) - 1; \
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size_t _size_ = size; \
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assert(_size_ <= ALLOCA_MAX); \
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_ptr_ = alloca((_size_ + _mask_) ?: 1); \
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(void*)(((uintptr_t)_ptr_ + _mask_) & ~_mask_); \
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})
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#define alloca0_align(size, align) \
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({ \
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void *_new_; \
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size_t _xsize_ = (size); \
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_new_ = alloca_align(_xsize_, (align)); \
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(void*)memset(_new_, 0, _xsize_); \
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})
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#if HAS_FEATURE_MEMORY_SANITIZER
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# define msan_unpoison(r, s) __msan_unpoison(r, s)
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#else
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# define msan_unpoison(r, s)
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#endif
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/* This returns the number of usable bytes in a malloc()ed region as per malloc_usable_size(), in a way that
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* is compatible with _FORTIFY_SOURCES. If _FORTIFY_SOURCES is used many memory operations will take the
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* object size as returned by __builtin_object_size() into account. Hence, let's return the smaller size of
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* malloc_usable_size() and __builtin_object_size() here, so that we definitely operate in safe territory by
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* both the compiler's and libc's standards. Note that __builtin_object_size() evaluates to SIZE_MAX if the
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* size cannot be determined, hence the MIN() expression should be safe with dynamically sized memory,
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* too. Moreover, when NULL is passed malloc_usable_size() is documented to return zero, and
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* __builtin_object_size() returns SIZE_MAX too, hence we also return a sensible value of 0 in this corner
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* case. */
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#define MALLOC_SIZEOF_SAFE(x) \
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MIN(malloc_usable_size(x), __builtin_object_size(x, 0))
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/* Inspired by ELEMENTSOF() but operates on malloc()'ed memory areas: typesafely returns the number of items
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* that fit into the specified memory block */
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#define MALLOC_ELEMENTSOF(x) \
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(__builtin_choose_expr( \
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__builtin_types_compatible_p(typeof(x), typeof(&*(x))), \
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MALLOC_SIZEOF_SAFE(x)/sizeof((x)[0]), \
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VOID_0))
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