null pointers should not be dereferenced

And the semantics, as I said, are different. Ticket opened : Thanks a lot for the minimalized reproducer ! But when length of A is 1, the control never reaches the else block. IDE extension that lets you fix coding issues before they exist! Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. 1 Answer Sorted by: 1 Your code is ok. When length is zero, it is probably unusable condition for this function. SonarQube Version 6.7.2 (build 37468) (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) Obviously the value of that pointer could have changed since the . A bug can cause them never to be reassigned. Thanks for contributing an answer to Stack Overflow! And fwstr > is dereferenced in the following codes. 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). 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]. I added an assertion to that compliant code example. Is there a single-word adjective for "having exceptionally strong moral principles"? My question is; is my solution incorrect? IDE extension that lets you fix coding issues before they exist! What are the effects of exceptions on performance in Java? The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. SIZE_MAX is the largest possible value that a size_t could take, so it is not possible to have anything larger than SIZE_MAX. When B is null, The control reaches inside the main if block only when length of A is 1. This will normally lead to an unhandled error, resulting in a segmentation fault. Trying to understand how to get this basic Fourier Series. What is pointed to should only be deleted if it was created with new. Mutually exclusive execution using std::atomic? Java Specification Participation Agreement version in use: 2.0. 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 */ Im having trouble understanding your problem. versions used (SonarQube, Scanner, language analyzer) 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). It also uses the unsigned type size_t to pass the length parameter, ensuring that negative values are not passed to func(). You need to benchmark. sonarqube Why does the second compliant example permit using possibly-null pointers? The 4gig boundary will probably be important too with unsigned int in LP64, but since size_t will be 64-bit, there will have to be some truncation that compilers will be able to warn on. Status: Dormant. Is there a solution to add special characters from software and how to do it, Acidity of alcohols and basicity of amines. . Whats the grammar of "For those whose stories they are"? Is it possible to rotate a window 90 degrees if it has the same length and width? The method isNR(minRating) is a helper method that validate among other things, if the object minRating is null. All rights are expressly reserved. NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. Powered by Discourse, best viewed with JavaScript enabled. that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. Many platforms can support testing for those also. 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. 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. A nonnegative return value represents the number of bytes successfully read (the return value is a "signed size" type, usually the native integer type for the target platform). 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?) 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 . Does Counterspell prevent from any further spells being cast on a given turn? . If copying takes place between objects that overlap, the behavior is undefined. Your assertion is not backed by the wording in the standard, nor by common implementer understanding. Is the God of a monotheism necessarily omnipotent? Thanks for contributing an answer to Stack Overflow! Instead use String.valueOf (object). 4. 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. SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. 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. Batch split images vertically in half, sequentially numbering the output files, Recovering from a blunder I made while emailing a professor. Connect and share knowledge within a single location that is structured and easy to search. Asking for help, clarification, or responding to other answers. Sonar detects that res.getBody() can be null when you do the check res.getBody()==null. The SonarJava SE engine is however, by default, not configured to explore methods declared in other files (in your case, your utility class CheckUtils). This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. positive S2637 in SonarQube 6.7.1 LTS, Sonar false positive, "change condition so that it does not always evaluate to true. When and how should I use a ThreadLocal variable? Making statements based on opinion; back them up with references or personal experience. Reports. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? But no where in that particular idiom would a NULL pointer necessarily be deferenced. Dereferencing > this null pointer may cause the kernel go wrong. If you preorder a special airline meal (e.g. How to tell which packages are held back due to phased updates. Issues Components. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. }. An awesome tip to avoid NPE is to return empty strings or empty collections rather than null. If you call connect() function, it better do the connection, but failing simply because some ptr is NULL is not good behaviour -- failures should . 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. 4500 Fifth Avenue 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. SonarJava. Alternate Terms Relationships Thanks for your relpy. 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. 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). I would also guess that pointers that point to the one-past-the-end of an array are also invalid. assert(!invalid(p)); // or whatever, bool invalid(const void *p) { Unfortunately, its actual state also has some limitations, like the one you are hitting here. java This issues is displayed by SonarQube. ncdu: What's going on with this second size column? sonar-java. The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. sonarLint (3.2.) 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. extern char _etext; 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. 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. In the complaint version, I like to make source code checking a little quicker by putting parenthesizes around arguments to |= or &= as. We can see that at obj.run(), obj can not be null, but is pointed out by Sonar. Passing ownership of something also requires pointers. How do you ensure that a red herring doesn't violate Chekhov's gun? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Pointer members in structs are not checked. Can you please start a new thread and be more explicit about the issue you are observing. 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. int changed to size_t and if size_t parameter's is zero, allocate one word. ability to run any cleanup processes. 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. What is the point of Thrower's Bandolier? NullPointerException is thrown when program attempts to use an object reference that has the null value. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. Null pointer should not be dereferenced , very old code or C code being worked into c++ may have functions that expect the user to delete the data. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. 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. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. I reordered that code example to do all the checks before allocations. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. What is null pointer exception in android. . 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. Find centralized, trusted content and collaborate around the technologies you use most. This code also violates ERR33-C. Detect and handle standard library errors. SonarJava Version 5.9.2 (build 16552). the Java one). io.NotSerializableException : java. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. This sounds indeed like a bug in the flow when an exception is raised. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). SonarQube - Null Pointer Dereference Issue java simonsirak (Simon Sirak) June 14, 2018, 1:18pm 1 Hi! In C, dereferencing a null pointer is undefined behavior. When B is null, The control reaches inside the main if block only when length of A is 1. We really appreciate your help. Currently I'm working with SonarQube solving issues but I'm facing a trouble to how handle null pointers that shouldn't be dereferenced. A null pointer in this position causes the read system call to fail with -EINVAL ("Invalid argument"). A reference to null should never be dereferenced/accessed. in above code, rev2023.3.3.43278. To learn more, see our tips on writing great answers. Linear regulator thermal information missing in datasheet, Identify those arcade games from a 1983 Brazilian music video. 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. Goal This cross-file approach analysis can be quite resource-consuming, and we are not ready to openly enable the feature. (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). Recovering from a blunder I made while emailing a professor. Explain about call by reference with an . 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. Key here (explains table format and definitions), EXP34-C = Union( CWE-690, list) where list =. uninitialized reference-type class members. Also, the term 'pointer' is bad (but maybe it comes from the FindBugs tool): Java doesn't have pointers, it has references. 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. () At this point we define size as strlen(input_str) + 1. However there is no portable way to verify that the pointer is valid, other than checking for null. Finally my method is returning a response with value of restTemplate. This is a matter of style, and also following code walkthrough. This code also violates ERR33-C. Detect and handle standard library errors. If you write [ref], then a null pointer is not allowed, but if you write [unique], then a null pointer is permitted. Believing that dereferencing NULL shouldn't crash the system doesn't make it true. https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx 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. Sonar is ok. 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. When I scan with sonar-lint in idea, it seams white list is useful, but when use sonar-scanner, always FP, org.springframework.util.CollectionUtils#isEmpty Write a semantic patch to nd cases where the result of calling kmalloc is dereferenced with no previous NULL pointer test. Not the answer you're looking for? 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.. Please explain: Without this, we wont be able to help you. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Possible fix: Assign a valid address to the pointer in all branches of the conditional statement.. Pointer can point to dynamically allocated memory. Powered by Discourse, best viewed with JavaScript enabled. Why does Mister Mxyzptlk need to have a weakness in the comics? We resolved it by adding our tools path in the white list, and repackaging it. That is, sets equivalent to a proper subset via an all-structure-preserving bijection. At worst, it could expose debugging information that would be useful to an attacker or it could allow an Cause we need throw our own Runtime Exception, well-known methods wont help. Is there a proper earth ground point in this switch box? ), 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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>. What methods/tools can be used to determine the cause so that you stop the exception from causing the progra. When a variable is declared as being a pointer to type void, it is known as a generic pointer. Finally, there is the matter of the compliant solution. 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". When I added the not null validation as sonar suggest. Maybe one of these methods is already doing what your methods is doing, and could be considered as replacement. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? Sonar is ok. Sonar can't determine that the helper method did the null validation. 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. Then the reading of the buffer via bstr_printf() will then look at the pointer to process the final output. Even if the object is null in this case, it will not give an exception and will print ' null ' to the output stream. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. Seems the analizer don't recognice the logic with the funcional object Optional. When you have a variable of non-primitive type, it is a reference to an object. Not the answer you're looking for? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. (from res.getBody().getServiceResult() ). isEmpty(Collection collection) 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 That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. At best, such an exception will cause abrupt program termination. )}"); vegan) just to try it, does this inconvenience the caterers and staff? sometimes FP occurs. 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. PS: I also tried the code in android studio which uses Lint and got no warnings. - the incident has nothing to do with me; can I use this this way? What is a NullPointerException, and how do I fix it?,What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? Rule squid:S2259 is based on a Symbolic Execution (SE) engine. Provide a self-contained reproducer (zipped project?) Iflengthhas the value1, the addition yields 0, and png_malloc() subsequently returns a null pointer, which is assigned to chunkdata. Pittsburgh, PA 15213-2612 By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In some situations, however, dereferencing a null pointer can lead to the execution of arbitrary code [Jack 2007,van Sprundel 2006]. Best to cite C11 s7.24.2.1 here: The memcpy function copies n characters from the object pointed to by s2 into the object pointed to by s1. A pointer to null (the 0 memory address) should never be dereferenced/accessed. Is it possible to create a concave light? Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. 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). Making statements based on opinion; back them up with references or personal experience. Thank you for clarifying your assertion until I understood it properly. Thered be huge value in jumping onto the latest version of the ecosystem (notably SonarQube), and benefit from all latest analyzers (e.g. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. NullPointerException is a RuntimeException. Thus we should check > this kstrdup() operation. LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. Why do academics stay as adjuncts for years rather than move around? The issue arises when dereferenced pointers are used. Hi Andreas, Thanks for the feedback. 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. Find centralized, trusted content and collaborate around the technologies you use most. The final NCCE is actually more insidious than it seems at first. Some Interesting Facts: 1) void pointers cannot be dereferenced. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. It's a modular system with the . Carnegie Mellon University We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. context.RaiseException . 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. res.getBody() == null || res.getBody().getServiceResult() == null). Shouldn't the function check all pointers before dereferencing them or passing them to another function? With their flexibility, void pointers also bring some constraints. To be precise, once length is changed to a size_t and cannot take negative values, it cannot have an invalid value. There are many ways to resolve this. Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). All content is copyright protected. 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. This is indeed an obvious False Positive from the rule. After that, you call res.getBody() again. Such long getter chains can also be replaced with Optional + map + ifPresent lambda style. 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. Perhaps this could be done with a special constraint that will notify the SE engine that we learned from a Debug.Assert call. 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. I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? I am a student implementing stack with singly linked list using C, following a book called Fundamentals of Data Structures in C.. Is there a proper earth ground point in this switch box? So the SIZE_MAX check was unnecessary. The method takes a relation name r as input, executes the query "select * from r," and prints the result out in tabular format with the attribute names displayed in the table's header; the attribute names are displayed in the table's header. name result . 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 "After the incident", I started to be more careful not to trip over things. . Trying to understand how to get this basic Fourier Series. So we have to check all the arguments before performing any actions. In particular, ROSE ensures that any pointer returned by malloc(), calloc(), or realloc() is first checked for NULL before being used (otherwise, it is free()-ed). On many platforms, dereferencing a null pointer results in abnormal program termination, but this is not required by the standard. Doing so will cause a NullReferenceException to be thrown. When exploring such methods, the engine then deduces behaviors regarding null-checking (among other things). 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. SonarLint IntelliJ 4.0.0.2916 Java Rule 'Null pointers should not be dereferenced' I'm getting this fault in the next code when obj can't be null in any scenario. can have the value zero on a call to that function. At At worst, it could expose debugging information that would be useful to an attacker, or . Using platform-specific means (e.g. For example the following program doesn't compile. Basically, yes. 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]. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The alert is related to the sonar rule : Null pointers should not be dereferenced. 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?) Dereferencing a null pointer results in undefined behavior. sonarlint complains that My main problem is because I'm doing a restTemplate.exchange with try-catch and declaring a variable with null value before the clause try and then using it inside the try. All content is copyright protected. If malloc() fails, it returns a null pointer that is assigned to c_str. 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. Whoops, you're right. Solution 1, it looks like, today's solution tomorrow's problem.

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