This compliant solution ensures that the pointer returned by png_malloc() is not null. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. We cannot understand how there could be a null pointer exception at the reported line. ", 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". Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. Powered by Discourse, best viewed with JavaScript enabled. I would also guess that pointers that point to the one-past-the-end of an array are also invalid. Thank you for clarifying your assertion until I understood it properly. False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. 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. Doing so will cause a NullPointerException to be thrown. My question is; is my solution incorrect? 4500 Fifth Avenue
Interactions/interfaces with C can't use references. (/). To learn more, see our tips on writing great answers. You can use Optional instead. 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. Not the answer you're looking for? The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. @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. When and how should I use a ThreadLocal variable? The article easily misleads the reader into believeing that ensuring pointer validity boils down to checking for pointer being not equal to NULL. It's a modular system with the . 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. What does it mean that a reference must refer to an object, not a dereferenced null pointer? What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Thanks for the feedback. There can be a null pointer type for each pointer type, such as a pointer to a character or a pointer to an integer, although this is . 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. Accessing or modifying a null object's field. Isn't easier just to check valid range of length? 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. So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). If you call connect() function, it better do the connection, but failing simply because some ptr is NULL is not good behaviour -- failures should . Is it suspicious or odd to stand by the gate of a GA airport watching the planes? PS: I also tried the code in android studio which uses Lint and got no warnings. On the command prompt, the same arguments work and the record is added in db but not when I call the stored procedure from inside java program CallableStatement insertStat = db_conn.prepareCall (" {call InsertCourses (?,?,?,?,?,?,?,? 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. Why do academics stay as adjuncts for years rather than move around? I am a student implementing stack with singly linked list using C, following a book called Fundamentals of Data Structures in C.. Currently I'm working with SonarQube solving issues but I'm facing a trouble to how handle null pointers that shouldn't be dereferenced. The only potential null is the return value of list(). All rights are expressly reserved. assert(!invalid(p)); // or whatever, bool invalid(const void *p) { What is pointed to should only be deleted if it was created with new. res.getBody() == null || res.getBody().getServiceResult() == null). Shouldn't the function check all pointers before dereferencing them or passing them to another function? 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. Depending on whether the pointer is valid (i.e. versions used (SonarQube, Scanner, language analyzer) At worst, it could expose debugging information that would be useful to an attacker, or 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 . 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 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" Aaron:I suspect we are talking past each other. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. 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. The Clang Static Analyzer already has a checker to find the null pointer dereference in code, however it is not sufficient for higher abstractions such as C++ smart pointers or optionals. Trying to understand how to get this basic Fourier Series. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). 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. in above code, Doing so will at best cause abrupt program termination, without the 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. Minimising the environmental effects of my dyson brain. Some Interesting Facts: 1) void pointers cannot be dereferenced. Solution 1, it looks like, today's solution tomorrow's problem. Is it possible to rotate a window 90 degrees if it has the same length and width? Here is our source code: Sign in to download full-size image . In C, dereferencing a null pointer is undefined behavior. sonarqube Making statements based on opinion; back them up with references or personal experience. 11 Sep, 2006. Cause we need throw our own Runtime Exception, well-known methods wont help. 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). How do you ensure that a red herring doesn't violate Chekhov's gun? There are other problems with this code, as is noted in the rule. Description: This JSR will work to develop standard annotations (such as @NonNull) that can be applied to Java programs to assist tools that detect software defects. Since you cannot have a variable of type void, the pointer will not point to any data and therefore cannot be dereferenced. raiseException() return, Sonar This topic was automatically closed 7 days after the last reply. What is a serialVersionUID and why should I use it? In this case, the difference is the assumption thatmalloc() always returns non-nullfor the second NCCE, whereas the first NCCE has themalloc() abstracted away. 412-268-5800, 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 pointer. How can this new ban on drag possibly be considered constitutional? 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(). specifies the length of the array for a function. The correct idiom is to only allocate storage if the pointer is currently NULL. Now, you can find the list of whitelisted methods here. 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. A reference to Nothing should never be dereferenced/accessed. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. But what exactly does it mean to "dereference a null pointer"? What does "Could not find or load main class" mean? Explain about call by reference with an . I added an assertion to that compliant code example. Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. How do I align things in the following tabular environment? 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. Using Kolmogorov complexity to measure difficulty of problems? 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. Can I tell police to wait and call a lawyer when served with a search warrant? name result . . Is the God of a monotheism necessarily omnipotent? This is indeed an obvious False Positive from the rule. This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. I have a sonar alert on this call minRating.getRatgCaam(). Hi @Michael! Finally my method is returning a response with value of restTemplate. Does it just mean failing to correctly check if a value is null? This solution also ensures that theuser_data pointer is not null. Sonar is ok. Sonar can't determine that the helper method did the null validation. best, such an exception will cause abrupt program termination. And the semantics, as I said, are different. Thanks for contributing an answer to Stack Overflow! Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). Good question! 4. This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. (from res.getBody().getServiceResult() ). Things go fine now. This is a matter of style, and also following code walkthrough. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures. What methods/tools can be used to determine the cause so that you stop the exception from causing the progra. That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. 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. Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. Sonar is ok. Connect and share knowledge within a single location that is structured and easy to search. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? [4] 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. At worst, it could expose debugging information that would be useful to an attacker or it could allow an In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. 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. Software Engineering Institute
Small typo nit: "such as if i t pointed to freed memory" meant to say "if it" instead (removing whitespace). Then we hit memcpy with length 0. Which @NotNull Java annotation should I use? It also uses the unsigned type size_t to pass the length parameter, ensuring that negative values are not passed to func(). It could be non-null the first time but not the second time, sonar does not know this. Check whether a String is not Null and not Empty. This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. 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. Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. context.RaiseException . Basically, yes. public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . Finally, there is the matter of the compliant solution. Why does the second compliant example permit using possibly-null pointers? A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. Whoops, you're right. I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. Pointer members in structs are not checked. 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. Is there a single-word adjective for "having exceptionally strong moral principles"? 3.Null pointers should not be derefer enced/accessed. Identify where the allocation occurs. Obviously the value of that pointer could have changed since the . That makes sense. The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. Correct; a null pointer is not a valid pointer for the C library functions. sonarlint complains that Status: Dormant. It's still illegal. 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. Even if the object is null in this case, it will not give an exception and will print ' null ' to the output stream. 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. 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. If you write [ref], then a null pointer is not allowed, but if you write [unique], then a null pointer is permitted. JCP version in use: 2.6. Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. One could argue that all code examples would be redundant with the first pair. Made code more compliant with other rules. Avoid Returning null from Methods. Issues Components. Is there a proper earth ground point in this switch box? We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. Likewise, pointers to freed memory are not valid. In some situations, however, dereferencing a null pointer can lead to the execution of arbitrary code [Jack 2007,van Sprundel 2006]. 3.7. 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. Why does Mister Mxyzptlk need to have a weakness in the comics? I reordered that code example to do all the checks before allocations. In C/C++ speak, 'dereferencing' simply means getting the object that a pointer . SonarLint: A "NullPointerException" could be thrown; "getBody()" can return null. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How do you ensure that a red herring doesn't violate Chekhov's gun? 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). Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. ii. extern char _etext; Many platforms can support testing for those also. Report False-positive / False-negative [LTS] The new SonarQube LTS is here: SONARQUBE 9.9 LTS, SonarQube - Null Pointer Dereference Issue. Thered be huge value in jumping onto the latest version of the ecosystem (notably SonarQube), and benefit from all latest analyzers (e.g. 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>. Can I tell police to wait and call a lawyer when served with a search warrant? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Possible fix: Assign a valid address to the pointer in all branches of the conditional statement.. Pointer can point to dynamically allocated memory. SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. Maybe one of these methods is already doing what your methods is doing, and could be considered as replacement. I have checked on multiple . The solution that I recommend is not work with null returns or variables on Java, try to avoid it. can have the value zero on a call to that function. Asking for help, clarification, or responding to other answers. 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? A pointer to null (the 0 memory address) should never be dereferenced/accessed. 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.) This issues is displayed by SonarQube. When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. SonarQube null pointers should not be dereferenced on try/catch, Sonarcube :Null pointers should not be dereferenced, How do you get out of a corner when plotting yourself into a corner. Null pointer should not be dereferenced , rev2023.3.3.43278. As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. However there is no portable way to verify that the pointer is valid, other than checking for null. null(java.lang.NullPointerException) . , RemoteContext new ExceptionType() RemoteContext , SonarLintJava (), java - sonarLint "Null pointers should not be dereferenced (squid:S2259)"Stack Overflow Is there a proper earth ground point in this switch box? Dereferencing a null pointer is undefined behavior. CWE-476: NULL Pointer Dereference: 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. Find centralized, trusted content and collaborate around the technologies you use most. 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. SonarJava Version 5.9.2 (build 16552). Recovering from a blunder I made while emailing a professor. Im currently using SonarQube version 5.6.6. better way to handle this is to store the result of method invocation in a variable. In the code, we check the not nullity with java.util.Objects.nonNull(). It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); java How can we prove that the supernatural or paranormal doesn't exist? positive S2637 in SonarQube 6.7.1 LTS, SonarQube for MSBuild not reporting quality issues, getTextContent() through "Null pointers should not be dereferenced". Now (sonarqube java analyzer version 4.3.0.7717) it's supported and works fine. int changed to size_t and if size_t parameter's is zero, allocate one word. The expected result here is solve the issue with sonarqube. At best, such an exception will cause abrupt program termination. When I added the not null validation as sonar suggest. isEmpty(Map map) 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. I suppose there is a question of "Is a pointer that points to 0 bytes valid?" Optimizers are optimizing based on this latitude and have been for years. The issue arises when dereferenced pointers are used. The same problem we will have with "Add at least one assertion to this test case."
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