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Merge pull request #1743 from pi-hole/new/zero_after_free 

NULL after free()
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DL6ER 2023-11-08 14:15:36 +01:00 committed by GitHub
parent b4ef3b5453 1f42708f14
commit ca0a3e50b8
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 13 additions and 4 deletions
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2
src/FTL.h
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@ -138,7 +138,7 @@
// caused by insufficient memory or by code bugs (not properly dealing
// with NULL pointers) much easier.
#undef strdup // strdup() is a macro in itself, it needs special handling
#define free(ptr) FTLfree(ptr, __FILE__, __FUNCTION__, __LINE__)
#define free(ptr) FTLfree((void**)&ptr, __FILE__, __FUNCTION__, __LINE__)
#define strdup(str_in) FTLstrdup(str_in, __FILE__, __FUNCTION__, __LINE__)
#define calloc(numer_of_elements, element_size) FTLcalloc(numer_of_elements, element_size, __FILE__, __FUNCTION__, __LINE__)
#define realloc(ptr, new_size) FTLrealloc(ptr, new_size, __FILE__, __FUNCTION__, __LINE__)

13
src/syscalls/free.c
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@ -13,17 +13,26 @@
#include "../log.h"
#undef free
void FTLfree(void *ptr, const char *file, const char *func, const int line)
void FTLfree(void **ptr, const char *file, const char *func, const int line)
{
// The free() function frees the memory space pointed to by ptr, which
// must have been returned by a previous call to malloc(), calloc(), or
// realloc(). Otherwise, or if free(ptr) has already been called before,
// undefined behavior occurs. If ptr is NULL, no operation is performed.
if(ptr == NULL)
{
log_warn("Trying to free NULL memory location in %s() (%s:%i)", func, file, line);
return;
}
if(*ptr == NULL)
{
log_warn("Trying to free NULL pointer in %s() (%s:%i)", func, file, line);
return;
}
free(ptr);
// Actually free the memory
free(*ptr);
// Set the pointer to NULL
*ptr = NULL;
}

2
src/syscalls/syscalls.h
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@ -14,7 +14,7 @@
char *FTLstrdup(const char *src, const char *file, const char *func, const int line) __attribute__((malloc));
void *FTLcalloc(size_t n, size_t size, const char *file, const char *func, const int line) __attribute__((malloc)) __attribute__((alloc_size(1,2)));
void *FTLrealloc(void *ptr_in, size_t size, const char *file, const char *func, const int line) __attribute__((alloc_size(2)));
void FTLfree(void *ptr, const char*file, const char *func, const int line);
void FTLfree(void **ptr, const char*file, const char *func, const int line);
int FTLfallocate(const int fd, const off_t offset, const off_t len, const char *file, const char *func, const int line);