null pointers should not be dereferenced

JCP version in use: 2.6. The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. isEmpty(Map map) 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 . We cannot understand how there could be a null pointer exception at the reported line. Now (sonarqube java analyzer version 4.3.0.7717) it's supported and works fine. Are there tables of wastage rates for different fruit and veg? I suggest that this topic needs to include calloc() and realloc() Refer to Linux man pages online for more enlightenment about malloc(), and friends. ncdu: What's going on with this second size column? PS: I also tried the code in android studio which uses Lint and got no warnings. The article easily misleads the reader into believeing that ensuring pointer validity boils down to checking for pointer being not equal to NULL. 1 Answer Sorted by: 1 Your code is ok. Small typo nit: "such as if i t pointed to freed memory" meant to say "if it" instead (removing whitespace). 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. And if there is no pointer_default declaration, then the default default is ref. ", 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". Is there a single-word adjective for "having exceptionally strong moral principles"? 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. PS: I also tried the code in android studio which uses Lint and got no warnings. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? @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. In C# and Java, all reference types can point to null. Not the answer you're looking for? Using Kolmogorov complexity to measure difficulty of problems? Identify where the allocation occurs. SonarQube Version 6.7.2 (build 37468) In Java, a special null value can be assigned to an object reference. 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" (from res.getBody().getServiceResult() ). 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). We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) Just because something is a pointer does not mean you should call delete . False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. Key here (explains table format and definitions), EXP34-C = Union( CWE-690, list) where list =. 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. the Java one). (I think you cover that in a different rule.) 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. I added an assertion to that compliant code example. I reordered that code example to do all the checks before allocations. At worst, it could expose debugging information that would be useful to an attacker, or Unlike reference types, pointer types are not tracked by the default garbage . Recovering from a blunder I made while emailing a professor. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures. IDE extension that lets you fix coding issues before they exist! There are other problems with this code, as is noted in the rule. Also, the term 'pointer' is bad (but maybe it comes from the FindBugs tool): Java doesn't have pointers, it has references. Two null pointers will always be equal to each other. that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. That makes sense. 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. Aaron:I suspect we are talking past each other. 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. That is, sets equivalent to a proper subset via an all-structure-preserving bijection. I am a student implementing stack with singly linked list using C, following a book called Fundamentals of Data Structures in C.. And fwstr > is dereferenced in the following codes. Making statements based on opinion; back them up with references or personal experience. And the semantics, as I said, are different. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. I feel my situation is not as complicated. public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. "After the incident", I started to be more careful not to trip over things. Unfortunately, its actual state also has some limitations, like the one you are hitting here. res.getBody() == null || res.getBody().getServiceResult() == null). At best, such an exception will cause abrupt program termination. . Maybe one of these methods is already doing what your methods is doing, and could be considered as replacement. Depending on whether the pointer is valid (i.e. This cross-file approach analysis can be quite resource-consuming, and we are not ready to openly enable the feature. A NULL pointer can be dereferenced when signatures are being verified on PKCS7 signed or signedAndEnveloped data. 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 learn more, see our tips on writing great answers. One could argue that all code examples would be redundant with the first pair. Is there a proper earth ground point in this switch box? A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. 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. can have the value zero on a call to that function. I added a comment to explain that SIZE_MAX is the limit of size_t. (C11, S7.24.2.1). , NPE : null-, . Likewise, pointers to freed memory are not valid. How do I align things in the following tabular environment? Perhaps this could be done with a special constraint that will notify the SE engine that we learned from a Debug.Assert call. 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]. 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. Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. So the SIZE_MAX check was unnecessary. I believe in this case, either expression would work. 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 To be precise, once length is changed to a size_t and cannot take negative values, it cannot have an invalid value. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. At This is a matter of style, and also following code walkthrough. At best, such an exception will cause abrupt program termination. Doing so will cause a NullReferenceException to be thrown. Sonar is ok. The result of calling such a helper function should be . name result . rev2023.3.3.43278. All content is copyright protected. http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The correct idiom is to only allocate storage if the pointer is currently NULL. Hello. Why does the second compliant example permit using possibly-null pointers? What is a NullPointerException, and how do I fix it?,What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? 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. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. SonarJava Version 5.9.2 (build 16552). By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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]. So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). It also uses the unsigned type size_t to pass the length parameter, ensuring that negative values are not passed to func(). Instead use String.valueOf (object). Description The program can potentially dereference a null pointer, thereby raising a NullPointerException. Can I tell police to wait and call a lawyer when served with a search warrant? sonarqube Find centralized, trusted content and collaborate around the technologies you use most. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Write a semantic patch to nd cases where the result of calling kmalloc is dereferenced with no previous NULL pointer test. The SonarJava SE engine is however, by default, not configured to explore methods declared in other files (in your case, your utility class CheckUtils). A null pointer stores a defined value, but one that is defined by the environment to not be a valid address for any member or object. This code also violates ERR33-C. Detect and handle standard library errors. 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. Appropriate typecasting is necessary. 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. Making statements based on opinion; back them up with references or personal experience. 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. sonarLint (3.2.) I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). Share Improve this answer Follow answered Oct 5, 2017 at 16:27 I have a sonar alert on this call minRating.getRatgCaam(). When B is null, The control reaches inside the main if block only when length of A is 1. There is a missing check for the return value from . Thanks, David! A pointer to null (the 0 memory address) should never be dereferenced/accessed. We resolved it by adding our tools path in the white list, and repackaging it. . If you say [in] or [out] without a modifier, then the modifier defaults to the pointer_default for the enclosing class. What does it mean that a reference must refer to an object, not a dereferenced null pointer? ), 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. Not the answer you're looking for? My question is; is my solution incorrect? in above code, If you try to access any member variables or methods with that variable, you are trying to dereference it. (/). > Further, if kstrdup() returns NULL, we should return ERR_PTR(-ENOMEM) to > the caller site. which version of SonarQube are you using? 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. assert(!invalid(p)); // or whatever, bool invalid(const void *p) { 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. I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? 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(). This issues is displayed by SonarQube. Ticket opened : Thanks a lot for the minimalized reproducer ! Some Interesting Facts: 1) void pointers cannot be dereferenced. In the meantime, Im locking this thread. The only potential null is the return value of list(). Thanks for contributing an answer to Stack Overflow! Alternate Terms Relationships How can we prove that the supernatural or paranormal doesn't exist? At this point we define size as strlen(input_str) + 1. The user_data pointer could be invalid in other ways, such as pointing to freed memory. What are the effects of exceptions on performance in Java? 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. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. sometimes FP occurs. That is only true if possibleNumbers contains no element.. BTW: none of these warnings are shown by . 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). very old code or C code being worked into c++ may have functions that expect the user to delete the data. How can this new ban on drag possibly be considered constitutional? 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 My below code where I'm calling a stored procedure is giving a null pointer exception. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. Then the reading of the buffer via bstr_printf() will then look at the pointer to process the final output. But passing 0 to memcpy() is not one of them. We can see that at obj.run(), obj can not be null, but is pointed out by Sonar. Pittsburgh, PA 15213-2612 Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. }. I suppose there is a question of "Is a pointer that points to 0 bytes valid?" Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. 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 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. What sort of strategies would a medieval military use against a fantasy giant? 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. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). 3.7. That is why I explicitly check for this in my attempted solution. 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>. When you have a variable of non-primitive type, it is a reference to an object. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Recovering from a blunder I made while emailing a professor. Is there a single-word adjective for "having exceptionally strong moral principles"? All rights are expressly reserved. Batch split images vertically in half, sequentially numbering the output files, Recovering from a blunder I made while emailing a professor. Optimizers are optimizing based on this latitude and have been for years. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How do I align things in the following tabular environment? I think that checking for user_data being NULL would be an improvement to the CS so long as there is an explicit mention that user_data being NULL is invalid even if length == 0. Provide a self-contained reproducer (zipped project?) The expected result here is solve the issue with sonarqube. Is it possible to create a concave light? specifies the length of the array for a function. In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. Iflengthhas the value1, the addition yields 0, and png_malloc() subsequently returns a null pointer, which is assigned to chunkdata. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Issues Components. Seems the analizer don't recognice the logic with the funcional object Optional. Why does Mister Mxyzptlk need to have a weakness in the comics? What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? IDE extension that lets you fix coding issues before they exist! 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. 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. On many platforms, dereferencing a null pointer results in abnormal program termination, but this is not required by the standard. Can you please start a new thread and be more explicit about the issue you are observing. Connect and share knowledge within a single location that is structured and easy to search. Is there a solution to add special characters from software and how to do it, Acidity of alcohols and basicity of amines. I've changed it to say null pointer instead of invalid pointer. 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. After that, you call res.getBody() again. 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. But no where in that particular idiom would a NULL pointer necessarily be deferenced. It looks like a logic bug, which can cause a memory leaking. Doing so will cause a NullPointerException to be thrown. https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx 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. Is null check needed before calling instanceof? void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. This likely means that youre on an ancient version of the Java analyzer. Shouldn't the function check all pointers before dereferencing them or passing them to another function? I don't need to do this validation again. Possible fix: Assign a valid address to the pointer in all branches of the conditional statement.. Pointer can point to dynamically allocated memory. A reference to null should never be dereferenced/accessed. What is generic pointer? If you preorder a special airline meal (e.g. This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. Not the answer you're looking for? In the code, we check the not nullity with java.util.Objects.nonNull(). In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. 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. Now, you can find the list of whitelisted methods here. Trying to understand how to get this basic Fourier Series. For the time being, I would unfortunately recommend to mark as False Positive the issue. Issues Components. Interactions/interfaces with C can't use references. A reference to null should never be dereferenced/accessed. Powered by Discourse, best viewed with JavaScript enabled. Asking for help, clarification, or responding to other answers. (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). How to tell which packages are held back due to phased updates. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? extern char _etext; 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.

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