To learn more, see our tips on writing great answers. Thank you for clarifying your assertion until I understood it properly. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. specifies the length of the array for a function. The fact that you can't pass a null (no object) with a reference parameter can be a reason to use a pointer instead. Powered by Discourse, best viewed with JavaScript enabled. Search for vulnerabilities resulting from the violation of this rule on the CERT website. Is there a single-word adjective for "having exceptionally strong moral principles"? 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. Iflengthhas the value1, the addition yields 0, and png_malloc() subsequently returns a null pointer, which is assigned to chunkdata. 1 Answer Sorted by: 2 Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. 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. Now, you can find the list of whitelisted methods here. I'd guess null pointers are not valid, even though they point to 0 bytes. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? The test was added to catch the possibly theoretical situation where the length of input_str was somehow the maximum size for size_t, and adding one to this size in the malloc expression (to allocated space for the trailing null byte) results in an integer overflow. NullPointerException is thrown when program attempts to use an object reference that has the null value. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. See "Clever Attack Exploits Fully-Patched Linux Kernel" [Goodin 2009] for an example of a code execution exploit that resulted from a null pointer dereference. Replacing broken pins/legs on a DIP IC package, Bulk update symbol size units from mm to map units in rule-based symbology, How do you get out of a corner when plotting yourself into a corner. 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" Is the God of a monotheism necessarily omnipotent? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 4500 Fifth Avenue Accessing or modifying a null object's field. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 4. In Java, a special null value can be assigned to an object reference. Software Engineering Institute Thanks for your relpy. If malloc() fails, it returns a null pointer that is assigned to c_str. It's even called out explicitly in C17 7.24.1p2: Where an argument declared as size_t n specifies the length of the array for a function, n can have the value zero on a call to that function. The above check can't hurt, as I guess you could have a system with a 32-bit size_t that had a ton of memory and had some crazy banking/selector scheme with pointers. Please explain: Without this, we wont be able to help you. Extended Description NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. All content is copyright protected. @Tibor SonarQube version 5.6.6, IntelliJ SonarLint plugin 3.0.0.2041, Sonar: Null pointers should not be dereferenced, How Intuit democratizes AI development across teams through reusability. The user_data pointer could be invalid in other ways, such as pointing to freed memory. 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. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). We have a false positive with the " Null pointers should not be dereferenced -squid:S2259" rule : We have a "NullPointerException" false positive for which we do not know how to solve it. You're in a company-managed project. Why does the second compliant example permit using possibly-null pointers? Doing so will cause a NullReferenceException to be thrown. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? So let me be more precise in my wording: I assert that a platform whose memcpy() did anything besides copy zero bytes when given n=0 and valid src and dest pointers was not C-standards-compliant. Using Kolmogorov complexity to measure difficulty of problems? The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. The approximation of the try catch flow is such that we consider an exception can be thrown just after the curly brace of the try. If copying takes place between objects that overlap, the behavior is undefined. Passing ownership of something also requires pointers. When you have a variable of non-primitive type, it is a reference to an object. In layman's terms, a null pointer is a pointer to an address in the memory space that does not have a meaningful value and cannot be referenced by the calling program, for whatever reason. Rule squid:S2259 is based on a Symbolic Execution (SE) engine. A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. I already tried to put ResponseEntity responseDto inside my try clause assigning and returning the respective value but its mandatory to return something out the try/catch. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This solution also ensures that theuser_data pointer is not null. In the code, we check the not nullity with java.util.Objects.nonNull(). Is there a single-word adjective for "having exceptionally strong moral principles"? parsing /proc/self/maps under linux) one might find out whether the pointer points into mapped memory, but this is still not a guarantee of validity because it is very coarse-grained see again the above example. The result of calling such a helper function should be . To learn more, see our tips on writing great answers. return p == NULL || (char *)p < &_etext; Unless explicitly stated otherwise in the description of a particular function in this subclause, pointer arguments on such a call shall still have valid values, as described in 7.1.4. And the semantics, as I said, are different. Sonar is ok. Unless explicitly stated otherwise in the description of a particular function in this subclause, pointer arguments on such a call shall still have valid values, as described in 7.1.4. That interpretation of the standard is not supported universally. Does Java have support for multiline strings? 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. I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. I've changed it to say null pointer instead of invalid pointer. You can compare a pointer with NULL to test for the special condition. It is generally accepted that zeroing a pointer is a good way to mark it as invalid and dereferencing an invalid pointer is a bug. This noncompliant code example is derived from a real-world example taken from a vulnerable version of the libpng library as deployed on a popular ARM-based cell phone [Jack 2007]. At worst, it could expose debugging information that would be useful to an attacker or it could allow an Finally my method is returning a response with value of restTemplate. PS: I also tried the code in android studio which uses Lint and got no warnings. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, SonarQube null pointers should not be dereferenced on try/catch, How Intuit democratizes AI development across teams through reusability. There is no legitimate reason to dereference a null pointer unless you on a rare system that maps page zero (or you intend your program to crash). sonar-java. However, memory allocation > functions such as kstrdup() may fail and returns NULL. 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". which version of SonarQube are you using? 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. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); You can use Optional instead. For the time being, I would unfortunately recommend to mark as False Positive the issue. Find centralized, trusted content and collaborate around the technologies you use most. rev2023.3.3.43278. Connect and share knowledge within a single location that is structured and easy to search. Appropriate typecasting is necessary. 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. ucsi->connector gets dereferenced by both ucsi_connector_change() and ucsi_resume(), both check for ucsi->connector being NULL in case ucsi_init() has not finished yet; or in case ucsi_init() has failed. This topic was automatically closed 7 days after the last reply. Because null pointer dereferencing is undefined behavior, the compiler (GCC in this case) can optimize away the if (!tun) check because it is performed after tun->sk is accessed, implying that tun is non-null. When a variable is declared as being a pointer to type void, it is known as a generic pointer. In C, dereferencing a null pointer is undefined behavior. This is indeed a false positive because, at time of writing, the sonarqube java analyzer (version 4.2.1 at time of writing) does not support cross procedural analysis and so it is not able to determine that indeed, for the condition to be true, the value of minRating has to be non null. 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 I added the not null validation as sonar suggest. Fixed by #1156 Contributor 94cb5f8 boris-unckel on Jul 28, 2021 9e62550 boris-unckel mentioned this issue on Jul 28, 2021 Closes #1155 - Null pointers should not be dereferenced #1156 Merged Just because something is a pointer does not mean you should call delete . We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. We cannot understand how there could be a null pointer exception at the reported line. context.RaiseException . . Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. How can we prove that the supernatural or paranormal doesn't exist? Why are physically impossible and logically impossible concepts considered separate in terms of probability? Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Because null pointer dereferencing is UB, the if (!tun) check can be elided entirely by the optimizer (since the tun->sk implies that tun must be non-null). This code also violates ERR33-C. Detect and handle standard library errors. Carnegie Mellon University context.RaiseException , (/) I think that checking for user_data being NULL would be an improvement to the CS so long as there is an explicit mention that user_data being NULL is invalid even if length == 0. 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). (in the meantime, in case of any other false-positive suspicion, make sure to check those latest versions as bunch of improvements are regularly released). In order to fix this, just do the following: BodyType body=res.getBody (); if (body == null || body.getServiceResult () == null) { return; } You can then even reuse body after that. 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. Then we hit memcpy with length 0. Calls to extension methods are not reported because they can still operate on null values. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) A null pointer in this position causes the read system call to fail with -EINVAL ("Invalid argument"). This likely means that youre on an ancient version of the Java analyzer. PS: I also tried the code in android studio which uses Lint and got no warnings. 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. isEmpty(Map map) Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. Perhaps this could be done with a special constraint that will notify the SE engine that we learned from a Debug.Assert call. As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. It could be non-null the first time but not the second time, sonar does not know this. Should trycatch go inside or outside a loop? Cause we need throw our own Runtime Exception, well-known methods wont help. util.regex.Matcher, java - Swing .getParent() . That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. On such a call, a function that locates a character finds no occurrence, a function that compares two character sequences returns zero, and a function that copies characters copies zero characters. Null pointer should not be dereferenced . 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, This error was found in the following code: else if (foo.list().length > 0) { }, I attempted to resolve this by rewriting as: else if (null != foo.list() && foo.list().length > 0) { }, foo is an instance of the File class in Java, and is directly instantiated through new File(). It's a modular system with the . What is a NullPointerException, and how do I fix it?,What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? However there is no portable way to verify that the pointer is valid, other than checking for null. What is the point of Thrower's Bandolier?