null pointers should not be dereferenced

null(java.lang.NullPointerException) . String *x, y; X is a pointer to a string, Y is a string & = address of variable/ operator || referencing operator * = value of address || dereferencing operator Pointers = stores memory address as its variables NULL pointer = a constant with a value of zero defined || assigned to null Void pointer = a pointer that is not associated with any data types New operator = denotes a request for . Handling Java NullPointerException and Best Practices - HowToDoInJava Description The program can potentially dereference a null pointer, thereby raising a NullPointerException. By 'valid pointers' I mean that both src and dest pointers are not null and they both point to non-overlapping arrays containing at least n bytes each. (I think you cover that in a different rule.) If the project is not compiled, and without sonar.java.binaries whether the white list takes effect? The indicated severity is for this more severe case; on platforms where it is not possible to exploit a null pointer dereference to execute arbitrary code, the actual severity is low. Please explain: Without this, we wont be able to help you. Iflengthhas the value1, the addition yields 0, and png_malloc() subsequently returns a null pointer, which is assigned to chunkdata. Why does Mister Mxyzptlk need to have a weakness in the comics? This is a matter of style, and also following code walkthrough. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. But when length of A is 1, the control never reaches the else block. Much like dereferencing a dangling (or wild) pointer leads to undefined behavior, dereferencing a null pointer also leads to undefined behavior. See C17 7.1.4p1, which says, in part: Each of the following statements applies unless explicitly stated otherwise in the detailed descriptions that follow: If an argument to a function has an invalid value (such as a value outside the domain of the function, or a pointer outside the address space of the program, or a null pointer, or a pointerto non-modifiable storage when the corresponding parameter is not const-qualified) or a type (after default argument promotion) not expected by a function with a variable number of arguments, the behavior is undefined. If that variable hasn't had a reference assigned, it's a null reference, which (for internal/historical reasons) is referred to as a null pointer. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. We might set a pointer to null even if we are not freeing a object, simply to dissociate one object from another: tty_driver->tty = NULL; /* detach low level driver from the tty device */ Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). If malloc() fails, it returns a null pointer that is assigned to c_str. In C, dereferencing a null pointer is undefined behavior. Pointers in C Explained - They're Not as Difficult - freeCodeCamp.org Is there a proper earth ground point in this switch box? Optimizers are optimizing based on this latitude and have been for years. I was fixing some issues gathered by SonarQube when I stumbled upon the following issue: "SonarQube violation: Possible null pointer dereference in ___ due to return value of called method" sonarlint complains that At worst, it could expose debugging information that would be useful to an attacker, or https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx How to get rid of NullPointerException - freeCodeCamp.org To create a custom null validation method declare an attribute with name ValidatedNotNullAttribute and mark the parameter that is Not the answer you're looking for? 0 is certainly within the 'domain of the function' (a phrase defined by mathematics but not by C11), as copying 0 bytes is well-understood (although silly). A pointer to null (the 0 memory address) should never be dereferenced/accessed. Original Java Specification Request (JSR) - Java Community Process Find centralized, trusted content and collaborate around the technologies you use most. Depending on whether the pointer is valid (i.e. Should trycatch go inside or outside a loop? Accessing or modifying a null object's field. C# static code analysis: HTTP responses should not be vulnerable to Could I capture, and I would be able to glean much security information from the dump? At this point we define size as strlen(input_str) + 1. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. (from res.getBody().getServiceResult() ). What does it mean that a reference must refer to an object, not a dereferenced null pointer? Small typo nit: "such as if i t pointed to freed memory" meant to say "if it" instead (removing whitespace). Removing the check "exception != null" raises S2259 "Null pointers should not be dereferenced" on "throw exception". Solution 1, it looks like, today's solution tomorrow's problem. A reference to Nothing should never be dereferenced/accessed. Using platform-specific means (e.g. SonarLint: A "NullPointerException" could be thrown; "getBody()" can return null. 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. ncdu: What's going on with this second size column? squid:S2259 : A "NullPointerException" could be thrown; "dc" is Some Interesting Facts: 1) void pointers cannot be dereferenced. Your assertion is not backed by the wording in the standard, nor by common implementer understanding. MSBuild SonarQube Runner Resharper Plugin receives skipping info errors File not in sonarqube, SonarQube jenkins plugin returns "Server returned HTTP response code: -1, message: 'null' for URL: https://api.github.com/user", SonarQube: Ignore issues in blocks not working with regex, sonarLint complains "Null pointers should not be dereferenced (squid:S2259)" despite that possibility being handled, Java: (false?) A pointer is simply a variable that contains a memory address. in above code, Reports. Ticket opened : Thanks a lot for the minimalized reproducer ! By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. You can compare a pointer with NULL to test for the special condition. We really appreciate your help. The value 0 for the number of bytes to copy is not what causes the UB, it's the null pointer value which triggers it. This latter use of pointers is a combined boolean/satellite: the pointer being non-null indicates "I have this sister object", and it provides that object. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures. New replies are no longer allowed. Sonar detects that res.getBody() can be null when you do the check res.getBody()==null. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? I believe that dereferencing NULL should not crash the system, should not allow a write to a NULL pointer area, but should always set errno, If I am a hacker, could I trap a null failure that would force a memory dump. Unfortunately, its actual state also has some limitations, like the one you are hitting here. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. CWE - CWE-476: NULL Pointer Dereference (4.10) - Mitre Corporation Is there a single-word adjective for "having exceptionally strong moral principles"? Find centralized, trusted content and collaborate around the technologies you use most. Things go fine now. Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. The issue arises when dereferenced pointers are used. IMHO, the rule title should be changed to something less general. Aaron:I suspect we are talking past each other. By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. The method isNR (minRating) is a helper method that validate among other things, if the object minRating is null public boolean isNR (AgencyRating rating) { return rating == null || isNR (rating.getRatgCaam ()); } When I added the not null validation as sonar suggest. All rights are expressly reserved. Identify where the allocation occurs. // <------- reported violation: NullPointerException might be thrown as 'bar' is nullable here, https://jira.sonarsource.com/browse/SONARJAVA-1490, https://groups.google.com/d/msgid/sonarqube/4752a999-246e-42c2-bbdc-8a44a5564ce9%40googlegroups.com. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. We can get a reference to point to null in the following ways: "uninitialized" reference type variables variables which are initialized with nulls and are assigned their real value afterward. points to memory allocated to the process) and what exactly was allocated there after the public key was freed, this may cause a segmentation fault or even execute code, which could again cause a segmentation fault, but might potentially be under the attacker's control. The libpng library implements its own wrapper to malloc() that returns a null pointer on error or on being passed a 0-byte-length argument. Calls to extension methods are not reported because they can still operate on null values. Do not use a null in a case where an object is required, https://gcc.gnu.org/gcc-4.9/porting_to.html, Prior to 2018-01-12: CERT: Unspecified Relationship, Pointer Casting and Pointer Type Changes [HFC], Dereferencing an out-of-domain pointer [nullref], Section 5.2.18, "Null-Pointer Dereference", Dereferencing null pointers that were not returned by a function. I say "theoretical" because I have not successfully produced strings of this length in testing. Do not dereference null pointers Created by Jeffrey Gennari, last modified by Jill Britton on Jan 18, 2023 Dereferencing a null pointer is undefined behavior. Then the reading of the buffer via bstr_printf() will then look at the pointer to process the final output. Status: Dormant. What methods/tools can be used to determine the cause so that you stop the exception from causing the progra. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. These can be: Invoking a method from a null object. )}"); Im very new to sonar, is there a way to add methods to the whitelist? My below code where I'm calling a stored procedure is giving a null pointer exception. As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. "After the incident", I started to be more careful not to trip over things. Is there a proper earth ground point in this switch box? Many platforms can support testing for those also. Write a semantic patch to nd cases where the result of calling kmalloc is dereferenced with no previous NULL pointer test. The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. The fact that you can't pass a null (no object) with a reference parameter can be a reason to use a pointer instead. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Null Pointers - Keil forum - Support forums - Arm Community best, such an exception will cause abrupt program termination. Yeah, I suspect once it's possible to allocate 2+gigs contiguously in amainstream install of a modern OS, we'll see a frenzy of new vulnerabilities come out. False fault 'Null pointers should not be dereferenced' using Optional Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, how to handle Sonarlint java:S2259 (Null pointers should not be dereferenced), How Intuit democratizes AI development across teams through reusability. When exploring such methods, the engine then deduces behaviors regarding null-checking (among other things). . ii. It's a modular system with the . Powered by Discourse, best viewed with JavaScript enabled. The same problem we will have with "Add at least one assertion to this test case." What is a serialVersionUID and why should I use it? Why do academics stay as adjuncts for years rather than move around? NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. I believe in this case, either expression would work. The chunkdata pointer is later used as a destination argument in a call to memcpy(), resulting in user-defined data overwriting memory starting at address 0. HTTP request redirections should not be open to forging attacks Deserialization should not be vulnerable to injection attacks Endpoints should not be vulnerable to reflected cross-site scripting (XSS) attacks "CoSetProxyBlanket" and "CoInitializeSecurity" should not be used Database queries should not be vulnerable to injection attacks The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. This compliant solution ensures that both input_str andthe pointer returned by malloc() are not null: This noncompliant code example is from a version of drivers/net/tun.c and affects Linux kernel 2.6.30 [Goodin 2009]: The sk pointer is initialized to tun->sk before checking if tun is a null pointer. , RemoteContext new ExceptionType() RemoteContext , SonarLintJava (), java - sonarLint "Null pointers should not be dereferenced (squid:S2259)"Stack Overflow 4. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Note that it doesn't know how to check for non-heap, non-stack. As a result, this noncompliant code example is vulnerable to a null pointer dereference exploit, because null pointer dereferencing can be permitted on several platforms, for example, by using mmap(2) with the MAP_FIXED flag on Linux and Mac OS X, or by using the shmat() POSIX function with the SHM_RND flag [Liu 2009]. Asking for help, clarification, or responding to other answers. res.getBody() == null || res.getBody().getServiceResult() == null). When a variable is declared as being a pointer to type void, it is known as a generic pointer. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? which version of SonarQube are you using? Thanks for contributing an answer to Stack Overflow! Not the answer you're looking for? Here is our source code: Sign in to download full-size image I could've fixed this by changing else to else if (B != null && B.length == 1), but doing so rewards me with warning "condition(B != null && B.length == 1) is always true". For the time being, I would unfortunately recommend to mark as False Positive the issue. S2259: Null pointers should not be dereferenced java tsubasa (Jiaoyang Ma) January 11, 2019, 6:57am 1 versions used (SonarQube, Scanner, language analyzer) SonarQube Version 6.7.2 (build 37468) SonarJava Version 5.9.2 (build 16552) minimal code sample to reproduce (with analysis parameter, and potential instructions to compile). Sonar is ok. Sonar can't determine that the helper method did the null validation. A non-null but invalid pointer passed to memcpy() can indeed cause undefined behavior, but that is not the issue in the noncompliant codethe pointer will either be valid or null. With their flexibility, void pointers also bring some constraints. Report False-positive / False-negative [LTS] The new SonarQube LTS is here: SONARQUBE 9.9 LTS, S2259: Null pointers should not be dereferenced, find the list of whitelisted methods here, Rule java:S2259: False-positive NullPointerException bug logged when variable is null-checked by an imported method, What is the issue you are observing, in details, What version of SonarSource products you are using, as well as the version of SonarJava.