Fix incorrect method name and idx.

[jiajunpei]

For some cases, name idx may exceed the range of u2, which will lead to a wrong method name resolve.

[jiajunpei]

@anestisb Hi, could you help review this commit?

[anestisb]

But number of methods is u2 so what is the exceed use case? Do you have a sample Dex file that you hit the bug?

[jiajunpei]

@anestisb Hi, what I really mean is that, the method's name id may exceed u2. You can refer to the definition of dexMethodId:

typedef struct __attribute__((packed)) {
  u2 classIdx;
  u2 protoIdx;
  u4 nameIdx;    // u4 here
} dexMethodId;

nameIdx is the type of u4, for the name resolution:

void dex_dumpMethodInfo(const u1 *dexFileBuf,
                        dexMethod *pDexMethod,
                        u4 localIdx,
                        const char *type) {
const char *methodName = dex_getStringDataByIdx(dexFileBuf, pDexMethodId->nameIdx);  // string resolution

And definition of function dex_getStringDataByIdx is:

const char *dex_getStringDataByIdx(const u1 *dexFileBuf, u2 idx) {  // but it's u2 here
  u4 unicode_length;
  return dex_getStringDataAndUtf16LengthByIdx(dexFileBuf, idx, &unicode_length);
}

The parameter of function dex_getStringDataByIdx is the type of u2.

So during the method name resolution, when calling function dex_getStringDataByIdx, there will be a Implicit conversion from u4 to u2. So if the name idx of a method exceed u2, the result of name resolution will be wrong.

I can't upload the dex file which can hit this bug due to security reasons, sorry for that.

[anestisb]

Gotcha. Yes you're absolutely right. Merging. Thank you for your contribution.