null pointers should not be dereferenced

Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. SonarJava Version 5.9.2 (build 16552). IDE extension that lets you fix coding issues before they exist! I suggest that this topic needs to include calloc() and realloc() Refer to Linux man pages online for more enlightenment about malloc(), and friends. Thered be huge value in jumping onto the latest version of the ecosystem (notably SonarQube), and benefit from all latest analyzers (e.g. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Sonar false-positive on rule: Null pointers should not be dereferenced, Null Pointer Dereference issue not detected when the pointer is returned by another function. That's true. minimal code sample to reproduce (with analysis parameter, and potential instructions to compile). Instead use String.valueOf (object). In C, dereferencing a null pointer is undefined behavior. What is generic pointer? Interactions/interfaces with C can't use references. . Currently I'm working with SonarQube solving issues but I'm facing a trouble to how handle null pointers that shouldn't be dereferenced. Why do academics stay as adjuncts for years rather than move around? And if there is no pointer_default declaration, then the default default is ref. sonarLint (3.2.) As for copy vs pointer/reference - it depends. You can use Optional instead. I reordered that code example to do all the checks before allocations. 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. the Java one). Your assertion is not backed by the wording in the standard, nor by common implementer understanding. rev2023.3.3.43278. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. At this point we define size as strlen(input_str) + 1. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) So you can declare a string t and then add characters to the string with a plus sign : t += 'a'; The code you are having issue with is just moving the pointer to the next character which the foreach is already doing. Find centralized, trusted content and collaborate around the technologies you use most. When B is null, The control reaches inside the main if block only when length of A is 1. If you write [ref], then a null pointer is not allowed, but if you write [unique], then a null pointer is permitted. Making statements based on opinion; back them up with references or personal experience. 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. Is there a proper earth ground point in this switch box? Please explain: Without this, we wont be able to help you. The result of calling such a helper function should be . validated for null in your method declaration with it: 2008-2023 SonarSource S.A., Switzerland. 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. Recovering from a blunder I made while emailing a professor. Possible fix: Assign a valid address to the pointer in all branches of the conditional statement.. Pointer can point to dynamically allocated memory. isEmpty(Collection collection) But what exactly does it mean to "dereference a null pointer"? On many platforms, dereferencing a null pointer results inabnormal program termination, but this is not required by the standard. Pittsburgh, PA 15213-2612 Software project. But no where in that particular idiom would a NULL pointer necessarily be deferenced. http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html. Thank you for clarifying your assertion until I understood it properly. In Java, a special null value can be assigned to an object reference. Null pointer should not be dereferenced . Thanks, David! The correct idiom is to only allocate storage if the pointer is currently NULL. sonarlint complains that Seems the analizer don't recognice the logic with the funcional object Optional. It is still a pointer though, to use it you just have to cast it to another kind of pointer first. All rights are expressly reserved. Two null pointers will always be equal to each other. Are there tables of wastage rates for different fruit and veg? rev2023.3.3.43278. Is the God of a monotheism necessarily omnipotent? That interpretation of the standard is not supported universally. To learn more, see our tips on writing great answers. 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. Does a summoned creature play immediately after being summoned by a ready action? Ticket opened : Thanks a lot for the minimalized reproducer ! Believing that dereferencing NULL shouldn't crash the system doesn't make it true. Finally my method is returning a response with value of restTemplate. name result . There are other problems with this code, as is noted in the rule. JCP version in use: 2.6. When you have a variable of non-primitive type, it is a reference to an object. 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". Thanks for contributing an answer to Stack Overflow! I don't need to do this validation again. Asking for help, clarification, or responding to other answers. In C# and Java, all reference types can point to null. My below code where I'm calling a stored procedure is giving a null pointer exception. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. 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.. 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. When and how should I use a ThreadLocal variable? IMHO, the rule title should be changed to something less general. Dereferencing a null pointer can lead to a denial of service. 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. When length is zero, it is probably unusable condition for this function. See the "Null pointer checks may be optimized away more aggressively" section inhttps://gcc.gnu.org/gcc-4.9/porting_to.htmlas an example with one common implementation. Find centralized, trusted content and collaborate around the technologies you use most. An awesome tip to avoid NPE is to return empty strings or empty collections rather than null. Is there a solution to add special characters from software and how to do it, Acidity of alcohols and basicity of amines. We can not disable any rule, sonar do validation in "Sonar way" (actual name of profile :) ), so we will need to mark them "Wont fix" each time it appear again in new code. 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. 1 Answer Sorted by: 1 Your code is ok. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? Batch split images vertically in half, sequentially numbering the output files, Recovering from a blunder I made while emailing a professor. It's a modular system with the . It also reinforces the notion to the reader that any time you see arithmetic in an allocation expression, you need to think about corner-cases. Dereferencing a null pointer is undefined behavior. If you try to access any member variables or methods with that variable, you are trying to dereference it. Powered by Discourse, best viewed with JavaScript enabled. The problem is, I hope this code's result to be <5,3> and <9,6> BUT the console only shows me <5,3> and <9,3>. 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?) ii. Removing the check "exception != null" raises S2259 "Null pointers should not be dereferenced" on "throw exception". What sort of strategies would a medieval military use against a fantasy giant? The final NCCE is actually more insidious than it seems at first. The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. That is, sets equivalent to a proper subset via an all-structure-preserving bijection. But when length of A is 1, the control never reaches the else block. 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. 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. Is the God of a monotheism necessarily omnipotent? Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. Thus we should check > this kstrdup() operation. Here is our source code: Sign in to download full-size image // <------- 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. There are many ways to resolve this. rev2023.3.3.43278. 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 . I'd guess null pointers are not valid, even though they point to 0 bytes. positive S2637 in SonarQube 6.7.1 LTS, SonarQube for MSBuild not reporting quality issues, getTextContent() through "Null pointers should not be dereferenced". You're in a company-managed project. Sonar detects that res.getBody() can be null when you do the check res.getBody()==null. The only potential null is the return value of list(). (I think you cover that in a different rule.) Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). Provide a self-contained reproducer (zipped project?) I have checked on multiple . 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. @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. which version of SonarQube are you using? Using Kolmogorov complexity to measure difficulty of problems? 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. )}"); sometimes FP occurs. Issues Components. 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. 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" 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. Trying to understand how to get this basic Fourier Series. Connect and share knowledge within a single location that is structured and easy to search. {"serverDuration": 214, "requestCorrelationId": "084acdc104f21c51"}, EXP34-C. Do not dereference null pointers, Clever Attack Exploits Fully-Patched Linux Kernel, ERR33-C. Detect and handle standard library errors, one compliant and one non-compliant example, CERT Oracle Secure Coding Standard for Java, EXP01-J. LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. Making statements based on opinion; back them up with references or personal experience. context.RaiseException . Can I tell police to wait and call a lawyer when served with a search warrant? So, this code should address the Sonar problem: You can also eliminate the null check using Optional>, like: Even I don't recommend this, you can just check the null responseDto without any use of Optional: Thanks for contributing an answer to Stack Overflow! But when length of A is 1, the control never reaches the else block. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). With their flexibility, void pointers also bring some constraints. Connect and share knowledge within a single location that is structured and easy to search. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. (C11, S7.24.2.1). That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. rev2023.3.3.43278. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. At worst, it could expose debugging information that would be useful to an attacker or it could allow an How to deal with "java.lang.OutOfMemoryError: Java heap space" error? Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Sonar is ok. Sonar can't determine that the helper method did the null validation. public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . Does Java have support for multiline strings? The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. Could I capture, and I would be able to glean much security information from the dump? The same problem we will have with "Add at least one assertion to this test case." 3.Null pointers should not be derefer enced/accessed. isEmpty(Map map) 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. The null pointer check for writing or dereferencing should be a compiler flag or library setting. In the complaint version, I like to make source code checking a little quicker by putting parenthesizes around arguments to |= or &= as. Shouldn't the function check all pointers before dereferencing them or passing them to another function? There are many ways to resolve this. Using platform-specific means (e.g. Issues Components. At I am a student implementing stack with singly linked list using C, following a book called Fundamentals of Data Structures in C.. sonarlint, sonarLint (3.2.) For the time being, I would unfortunately recommend to mark as False Positive the issue. ), Does not guess that return values from malloc(), strchr(), etc., can be NULL (The return value from malloc() is NULL only if there is OOMo and the dev might not care to handle that. static-code-analysis Not the answer you're looking for? But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. On many platforms, dereferencing a null pointer results in abnormal program termination, but this is not required by the standard. - the incident has nothing to do with me; can I use this this way? 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). We resolved it by adding our tools path in the white list, and repackaging it. Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). Why does Mister Mxyzptlk need to have a weakness in the comics? in above code, 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. If you say [in] or [out] without a modifier, then the modifier defaults to the pointer_default for the enclosing class. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? We. 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 . NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. All content is copyright protected. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); So we have to check all the arguments before performing any actions. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. [4] Then we hit memcpy with length 0. It means this is illegal: T* p = nullptr; T& r = *p; // illegal NOTE: Please do not email us saying the above works on your particular version of your particular compiler. 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. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. I have a sonar alert on this call minRating.getRatgCaam(). 3.7. 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 best, such an exception will cause abrupt program termination. Coverity Prevent cannot discover all violations of this rule, so further verification is necessary, Detects when NULL is dereferenced (Array of pointers is not checked. A bug can cause them never to be reassigned. Which @NotNull Java annotation should I use? 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. It could be non-null the first time but not the second time, sonar does not know this. In the simplest case, this function just returns the result of calling kmalloc. When B is null, The control reaches inside the main if block only when length of A is 1. Haiku is a free and open-source operating system for PC designed to be binary compatible with the BeOS operating system and embodying the basic ideas of BeOS. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. Likewise, pointers to freed memory are not valid. Made code more compliant with other rules. 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. A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. 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. ncdu: What's going on with this second size column? . 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. I would also guess that pointers that point to the one-past-the-end of an array are also invalid. context.RaiseException , (/) I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. Software Engineering Institute 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 By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. It could be non-null the first time but not the second time, sonar does not know this. How can we prove that the supernatural or paranormal doesn't exist? 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. Should trycatch go inside or outside a loop? Now, you can find the list of whitelisted methods here. Connect and share knowledge within a single location that is structured and easy to search. SonarQube Version 6.7.2 (build 37468) EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. A NULL pointer can be dereferenced when signatures are being verified on PKCS7 signed or signedAndEnveloped data. SonarQube - Null Pointer Dereference Issue java simonsirak (Simon Sirak) June 14, 2018, 1:18pm 1 Hi! How handle the initialization of "responseDto" without "null" because is throwing the issue on sonar. This solution also ensures that theuser_data pointer is not null. In the code, we check the not nullity with java.util.Objects.nonNull(). int changed to size_t and if size_t parameter's is zero, allocate one word. This topic was automatically closed 7 days after the last reply. 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. A reference to Nothing should never be dereferenced/accessed. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Search for vulnerabilities resulting from the violation of this rule on the CERT website. When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. 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 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. However, memory allocation > functions such as kstrdup() may fail and returns NULL. The alert is related to the sonar rule : Null pointers should not be dereferenced. What is null pointer exception in android. The issue is: memcpy() and friends do not explicitly state that a null pointer is a valid pointer value, even if the number of bytes to copy is 0. Isn't easier just to check valid range of length? I say "theoretical" because I have not successfully produced strings of this length in testing. Why is there a voltage on my HDMI and coaxial cables? Check whether a String is not Null and not Empty. 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. ", 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". 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. NullPointerException is a RuntimeException. I added an assertion to that compliant code example. Discover SonarLint SaaS Setup is effortless and analysis is automatic for most languages Discover SonarCloud Self-Hosted Fast, accurate analysis; enterprise scalability Discover SonarQube Secrets ABAP Im very new to sonar, is there a way to add methods to the whitelist? 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]. Making statements based on opinion; back them up with references or personal experience. 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.

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