Making statements based on opinion; back them up with references or personal experience. 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. Are there tables of wastage rates for different fruit and veg? Does a summoned creature play immediately after being summoned by a ready action? Solution 1, it looks like, today's solution tomorrow's problem. ), NPD.CHECK.CALL.MIGHTNPD.CHECK.CALL.MUSTNPD.CHECK.MIGHTNPD.CHECK.MUSTNPD.CONST.CALLNPD.CONST.DEREFNPD.FUNC.CALL.MIGHTNPD.FUNC.CALL.MUSTNPD.FUNC.MIGHTNPD.FUNC.MUSTNPD.GEN.CALL.MIGHTNPD.GEN.CALL.MUSTNPD.GEN.MIGHTNPD.GEN.MUSTRNPD.CALLRNPD.DEREF, 45 D, 123 D, 128 D, 129 D, 130 D, 131 D, 652 S, Checks for use of null pointers (rule partially covered). There are many ways to resolve this. java As for copy vs pointer/reference - it depends. Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. How can this new ban on drag possibly be considered constitutional? The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. Is the God of a monotheism necessarily omnipotent? Calls to extension methods are not reported because they can still operate on null values. Likewise, pointers to freed memory are not valid. Null pointers should not be dereferenced (#42) Issues - GitLab 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. This sounds indeed like a bug in the flow when an exception is raised. What does it mean that a reference must refer to an object, not a dereferenced null pointer? Revert Update S2259: "Null pointer dereference" CFG should ignore expressions in Debug.Assert #397 Introduce means to not raise "Expression always true/false" on values that were checked with Debug.Assert. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. It could be non-null the first time but not the second time, sonar does not know this. I feel my situation is not as complicated. When B is null, The control reaches inside the main if block only when length of A is 1. 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. The same problem we will have with "Add at least one assertion to this test case." COMP-PROG-MODULE-5-6-REVIEWER.pdf - Pointers to string Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Issues Components. I have checked on multiple . Report False-positive / False-negative [LTS] The new SonarQube LTS is here: SONARQUBE 9.9 LTS, SonarQube - Null Pointer Dereference Issue. All content is copyright protected. ncdu: What's going on with this second size column? The purpose of a NULL pointer is not to cause a processor exception when it is dereferenced (although that is nice to have for debugging.) A null pointer in this position causes the read system call to fail with -EINVAL ("Invalid argument"). Doing so will cause a NullPointerException to be thrown. 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. C static code analysis: Null pointers should not be dereferenced C static code analysis Unique rules to find Bugs, Vulnerabilities, Security Hotspots, and Code Smells in your C code All rules 311 Vulnerability 13 Bug 74 Security Hotspot 18 Code Smell 206 Quick Fix 14 Tags "memset" should not be used to delete sensitive data Vulnerability Mutually exclusive execution using std::atomic? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Sonar: Null pointers should not be dereferenced, Why should Java 8's Optional not be used in arguments, Sonar alert : "private" methods that don't access instance data should be "static", sonarLint complains "Null pointers should not be dereferenced (squid:S2259)" despite that possibility being handled, Java: (false?) 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. Answered: difference between a void pointer and a | bartleby SonarJava Version 5.9.2 (build 16552). 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. Why do academics stay as adjuncts for years rather than move around? Even if the object is null in this case, it will not give an exception and will print ' null ' to the output stream. A reference to null should never be dereferenced/accessed. OpenSSL Releases Security Update - NHS Digital Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. 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. 1. Introduction - Understanding and Using C Pointers [Book] Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Find centralized, trusted content and collaborate around the technologies you use most. In the case of the ARM and XScale architectures, the 0x0 address is mapped in memory and serves as the exception vector table; consequently, dereferencing 0x0 did not cause an abnormal program termination. Using Kolmogorov complexity to measure difficulty of problems? But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. Just because something is a pointer does not mean you should call delete . 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. There is no guarantee that subsequent invocations are returning the same value, thats why issue is raised. 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. 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. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . In case the hash algorithm used for the signature is known to the OpenSSL library but the implementation of the hash algorithm is not available the digest initialization will fail. ncdu: What's going on with this second size column? The solution that I recommend is not work with null returns or variables on Java, try to avoid it. 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. Why are physically impossible and logically impossible concepts considered separate in terms of probability? A value is checked here to see whether it is null, but this value can't be null because it was previously dereferenced and if it were null a null pointer exception would have occurred at the earlier dereference. At best, such an exception will cause abrupt program termination. While the engine is in practice already able to explore code from other files if needed (relying solely on bytecode), we restrain this approach to a limited set of well-known methods from standard libraries, for which we know that behaviors are correctly produced. In Java, a special null value can be assigned to an object reference. What is a NullPointerException, and how do I fix it? Void pointers cannot be dereferenced as any other pointer. Thanks, David! public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . The article easily misleads the reader into believeing that ensuring pointer validity boils down to checking for pointer being not equal to NULL. Unfortunately the problem is much more complex, and generally unsolvable within standard C. Consider the following example: There's no way f can check whether x points into valid memory or not. Whats the grammar of "For those whose stories they are"? Ticket opened : Thanks a lot for the minimalized reproducer ! This is a matter of style, and also following code walkthrough. 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. (from res.getBody().getServiceResult() ). rev2023.3.3.43278. SonarQube Version 6.7.2 (build 37468) An awesome tip to avoid NPE is to return empty strings or empty collections rather than null. Currently I'm working with SonarQube solving issues but I'm facing a trouble to how handle null pointers that shouldn't be dereferenced. Reference vs dereference pointers in arguments C++/C NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. ability to run any cleanup processes. 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. int changed to size_t and if size_t parameter's is zero, allocate one word. It looks like a logic bug, which can cause a memory leaking. That is why I explicitly check for this in my attempted solution. ", Eclipse - Sonar S2629 possible false positive with new String, SonarQube null pointers should not be dereferenced on try/catch, getTextContent() through "Null pointers should not be dereferenced". // <------- 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. Using Kolmogorov complexity to measure difficulty of problems? If the pointer is not NULL, see if the assignment occurs only in a branch of a conditional statement.Investigate when that branch does not execute. 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. If you try to access any member variables or methods with that variable, you are trying to dereference it. to 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. Sonar detects that res.getBody() can be null when you do the check res.getBody()==null. When length is zero, it is probably unusable condition for this function. isEmpty(Map map) We. Perhaps this could be done with a special constraint that will notify the SE engine that we learned from a Debug.Assert call. Then we hit memcpy with length 0. Powered by Discourse, best viewed with JavaScript enabled. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. Thank you for clarifying your assertion until I understood it properly. rev2023.3.3.43278. The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. However there is no portable way to verify that the pointer is valid, other than checking for null. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? sonar_etReines-CSDN So Bar might not be initialized but then the last line of your example should not be evaluated in this case. But when length of A is 1, the control never reaches the else block. Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, It is a false positive, but it might be a good idea not to do the, Sonar false-positive on rule: Null pointers should not be dereferenced, How Intuit democratizes AI development across teams through reusability. One could argue that all code examples would be redundant with the first pair. How do you ensure that a red herring doesn't violate Chekhov's gun? NULL POINTERS SHOULD NOT BE DEREFERENCED - jobhuntley.com There are other problems with this code, as is noted in the rule. By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. This code also violates ERR33-C. Detect and handle standard library errors. [RSPEC-2259] - Jira 11 Sep, 2006. At Is it possible to create a concave light? 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 . I suppose there is a question of "Is a pointer that points to 0 bytes valid?" Is null check needed before calling instanceof? U1 merged - It is a great text book for learning about linux devices. 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. Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. Unlike reference types, pointer types are not tracked by the default garbage . By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The expected result here is solve the issue with sonarqube. Also, the term 'pointer' is bad (but maybe it comes from the FindBugs tool): Java doesn't have pointers, it has references. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? So Bar might not be initialized but then the last line of your example should not be evaluated in this case. Hi @Michael! SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. 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. What should you do if somebody passes a null pointer for a parameter vegan) just to try it, does this inconvenience the caterers and staff? When exploring such methods, the engine then deduces behaviors regarding null-checking (among other things). 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. uninitialized reference-type class members. You need to benchmark. 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. util.regex.Matcher, java - Swing .getParent() . Because a null pointer does not point to a meaningful object, an attempt to dereference(i.e., access the data stored at that memory location) a null pointer usually (but not always) causes a run-time error or immediate program crash. Recovering from a blunder I made while emailing a professor. How do I align things in the following tabular environment? How to use java.net.URLConnection to fire and handle HTTP requests, Why should Java 8's Optional not be used in arguments, sonarLint complains "Null pointers should not be dereferenced (squid:S2259)" despite that possibility being handled. Small typo nit: "such as if i t pointed to freed memory" meant to say "if it" instead (removing whitespace). How to use Slater Type Orbitals as a basis functions in matrix method correctly? Dereferencing a null pointer is undefined behavior. This cross-file approach analysis can be quite resource-consuming, and we are not ready to openly enable the feature. https://stackoverflow.com/questions/47534436/, https://stackoverflow.com/questions/47534436/, java - Jenkins groovy : Error: java. This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. But passing 0 to memcpy() is not one of them. In some situations, however, dereferencing a null pointer can lead to the execution of arbitrary code [Jack 2007,van Sprundel 2006]. return p == NULL || (char *)p < &_etext; We cannot understand how there could be a null pointer exception at the reported line. rev2023.3.3.43278. java - sonarLint "Null pointers should not be (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). 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. Things go fine now. name result . By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. Made code more compliant with other rules. All rights are expressly reserved. A reference to Nothing should never be dereferenced/accessed. Interactions/interfaces with C can't use references. Shouldn't the function check all pointers before dereferencing them or passing them to another function? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Null Pointers - Keil forum - Support forums - Arm Community If malloc() fails, it returns a null pointer that is assigned to c_str. I say "theoretical" because I have not successfully produced strings of this length in testing. Making statements based on opinion; back them up with references or personal experience. > Further, if kstrdup() returns NULL, we should return ERR_PTR(-ENOMEM) to > the caller site. This is indeed an obvious False Positive from the rule. In C# and Java, all reference types can point to null. Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. ROSE does not handle cases where an allocation is assigned to an lvalue that is not a variable (such as a struct member or C++ function call returning a reference), Finds instances where a pointer is checked against NULL and then later dereferenced, Identifies functions that can return a null pointer but are not checked, Identifies code that dereferences a pointer and then checks the pointer against NULL, Can find the instances where NULL is explicitly dereferenced or a pointer is checked againstNULL but then dereferenced anyway. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. It does not point to any area of memory. Note that it doesn't know how to check for non-heap, non-stack. 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 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]. Software Engineering Institute . specifies the length of the array for a function. Asking for help, clarification, or responding to other answers. So the first execution of ValidateNumber inside the foreach works fine and valid is set to true.The second execution throws the exception and exception is set in the catch-Block.. What does "Could not find or load main class" mean? , NPE : null-, . When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. Review and Fix Illegally Dereferenced Pointer Checks 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. I believe in this case, either expression would work. Handling Java NullPointerException and Best Practices - HowToDoInJava Removing the check "exception != null" raises S2259 "Null pointers should not be dereferenced" on "throw exception". Analysis of Haiku Operating System (BeOS Family) by PVS-Studio. Part 1 static-code-analysis please explain null pointer dereference [Solved] (Java in General forum Aaron:I suspect we are talking past each other. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). FindBugs CORRECTNESS - And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). In the complaint version, I like to make source code checking a little quicker by putting parenthesizes around arguments to |= or &= as. Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. 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 Provide a self-contained reproducer (zipped project?) , . Off by one error: It is the third example. Dereferencing > this null pointer may cause the kernel go wrong. EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. ssize_t (*aio_read)(struct kiocb *, char __user *, size_t . Null Pointer Exception In Java - GeeksforGeeks - A computer science It's still illegal. 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). However, memory allocation > functions such as kstrdup() may fail and returns NULL. Minimising the environmental effects of my dyson brain. In the code, we check the not nullity with java.util.Objects.nonNull(). Correct; a null pointer is not a valid pointer for the C library functions. What is generic pointer? 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. I have a sonar alert on this call minRating.getRatgCaam(). Thanks for contributing an answer to Stack Overflow! Instead use String.valueOf (object). A pointer to null (the 0 memory address) should never be dereferenced/accessed. Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). Sonar violation: Null pointers should not be dereferenced #7459 - GitHub