Null pointer dereference in `qemu_ram_free` when HVA malloc fails

[liyansong2018]

When we try to use uc_mem_map to apply for super large memory, memory allocation in HAV fails, but succeeds in GVA. This inconsistency leads to null pointer dereference in us_ close release about the ram block requested by uc_mem_map.

PoC

int main(int argc, char **argv) {
    uc_engine *uc;
    uc_err err;
    err = uc_open(UC_ARCH_X86, UC_MODE_64, &uc);
    if (err != UC_ERR_OK) {
        printf("Failed on uc_open() with error returned: %u %s\n", err, uc_strerror(err));
        return -1;
    }

    err = uc_mem_map(uc, 0x0, 0xfffffffff000, UC_PROT_ALL);
    if (err != UC_ERR_OK) {
        printf("Failed on uc_open() with error returned: %u %s\n", err, uc_strerror(err));
        //return -1;
    }
    uc_close(uc);
    return 0;
}

output

$ ./poc_test
AddressSanitizer:DEADLYSIGNAL
=================================================================
==36945==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f6f0c61dc5f bp 0x7ffd6adc9320 sp 0x7ffd6adc9310 T0)                                                                                                                   
==36945==The signal is caused by a WRITE memory access.                                                                    
==36945==Hint: address points to the zero page.
    #0 0x7f6f0c61dc5f in qemu_ram_free_x86_64 /home/lys/Documents/my/unicorn/qemu/exec.c:1133
    #1 0x7f6f0c624483 in memory_region_destructor_ram /home/lys/Documents/my/unicorn/qemu/softmmu/memory.c:882
    #2 0x7f6f0c62269f in memory_free_x86_64 /home/lys/Documents/my/unicorn/qemu/softmmu/memory.c:182
    #3 0x7f6f0c6169da in release_common /home/lys/Documents/my/unicorn/qemu/unicorn_common.h:62
    #4 0x7f6f0c616cd3 in x86_release /home/lys/Documents/my/unicorn/qemu/target/i386/unicorn.c:47
    #5 0x7f6f0c60e4c5 in uc_close /home/lys/Documents/my/unicorn/uc.c:419
    #6 0x55955d1423e1 in main /home/lys/Documents/unitest/poc_test.c:60
    #7 0x7f6f0c0d47ec in __libc_start_main ../csu/libc-start.c:332
    #8 0x55955d142129 in _start (/home/lys/Documents/unitest/poc_test+0x1129)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /home/lys/Documents/my/unicorn/qemu/exec.c:1133 in qemu_ram_free_x86_64
==36945==ABORTING

[liyansong2018]

There are many ways to fix this bug. I will pull request with a simple patch later.

[wtdcode]

Fixed in 3d3deac