null pointers should not be dereferenced

I suppose there is a question of "Is a pointer that points to 0 bytes valid?" can have the value zero on a call to that function. In C# and Java, all reference types can point to null. uninitialized reference-type class members. Is it possible to create a concave light? Thank you for clarifying your assertion until I understood it properly. Null pointer should not be dereferenced , extern char _etext; False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. Doing so will cause a NullPointerException to be thrown. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. 3.7. Sonar is ok. Are there tables of wastage rates for different fruit and veg? Mutually exclusive execution using std::atomic? In this case, the difference is the assumption thatmalloc() always returns non-nullfor the second NCCE, whereas the first NCCE has themalloc() abstracted away. Is there a single-word adjective for "having exceptionally strong moral principles"? sonar-java. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. I added an assertion to that compliant code example. Is there a proper earth ground point in this switch box? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. positive S2637 in SonarQube 6.7.1 LTS, SonarQube for MSBuild not reporting quality issues, getTextContent() through "Null pointers should not be dereferenced". (from res.getBody().getServiceResult() ). Likewise, pointers to freed memory are not valid. [4] For the time being, I would unfortunately recommend to mark as False Positive the issue. I would therefore assert that a platform whose memcpy() did anything besides a no-op when given n=0 and valid source/destination pointers was not C-standards-compliant. Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. There are many ways to resolve this. Then the reading of the buffer via bstr_printf() will then look at the pointer to process the final output. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I'd guess WG14 has considered these questions, but I haven't until now :). Two null pointers will always be equal to each other. Batch split images vertically in half, sequentially numbering the output files, Difficulties with estimation of epsilon-delta limit proof, Minimising the environmental effects of my dyson brain. 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" Pittsburgh, PA 15213-2612 If copying takes place between objects that overlap, the behavior is undefined. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Things go fine now. Ticket opened : Thanks a lot for the minimalized reproducer ! Sonar detects that res.getBody() can be null when you do the check res.getBody()==null. 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?) Issues Components. The only potential null is the return value of list(). Such long getter chains can also be replaced with Optional + map + ifPresent lambda style. 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. positive S2637 in SonarQube 6.7.1 LTS, Sonar false positive, "change condition so that it does not always evaluate to true. This issues is displayed by SonarQube. Why does Mister Mxyzptlk need to have a weakness in the comics? util.regex.Matcher, java - Swing .getParent() . I believe in this case, either expression would work. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. 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. 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. Is it possible to create a concave light? 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. ROSE does not handle cases where an allocation is assigned to an lvalue that is not a variable (such as a struct member or C++ function call returning a reference), Finds instances where a pointer is checked against NULL and then later dereferenced, Identifies functions that can return a null pointer but are not checked, Identifies code that dereferences a pointer and then checks the pointer against NULL, Can find the instances where NULL is explicitly dereferenced or a pointer is checked againstNULL but then dereferenced anyway. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I reordered that code example to do all the checks before allocations. Obviously the value of that pointer could have changed since the . By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. But no where in that particular idiom would a NULL pointer necessarily be deferenced. Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. The standard will simply copy 0 byteswhich is essentially a no-op. I have a sonar alert on this call minRating.getRatgCaam(). Is null check needed before calling instanceof? It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); I'd guess null pointers are not valid, even though they point to 0 bytes. Instead use String.valueOf (object). Your assertion is not backed by the wording in the standard, nor by common implementer understanding. When B is null, The control reaches inside the main if block only when length of A is 1. It's a modular system with the . 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. Software project. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Here is our source code: Sign in to download full-size image All content is copyright protected. validated for null in your method declaration with it: 2008-2023 SonarSource S.A., Switzerland. (C11, S7.24.2.1). Thanks for contributing an answer to Stack Overflow! That's true. return p == NULL || (char *)p < &_etext; 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. It could be non-null the first time but not the second time, sonar does not know this. 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 Why are physically impossible and logically impossible concepts considered separate in terms of probability? Asking for help, clarification, or responding to other answers. You need to benchmark. minimal code sample to reproduce (with analysis parameter, and potential instructions to compile). ", 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". This likely means that youre on an ancient version of the Java analyzer. With their flexibility, void pointers also bring some constraints. Find centralized, trusted content and collaborate around the technologies you use most. 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. ii. 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. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. Trying to understand how to get this basic Fourier Series. 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. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? Is it suspicious or odd to stand by the gate of a GA airport watching the planes? 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. 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. Doing so will cause a NullReferenceException to be thrown. The user_data pointer could be invalid in other ways, such as pointing to freed memory. Status: Dormant. All rights are expressly reserved. Recovering from a blunder I made while emailing a professor. 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! (/). In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. This code also violates ERR33-C. Detect and handle standard library errors. 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. Is it possible to rotate a window 90 degrees if it has the same length and width? So we have to check all the arguments before performing any actions. () Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. How do I align things in the following tabular environment? And if there is no pointer_default declaration, then the default default is ref. It's still illegal. A value is checked here to see whether it is null, but this value can't be null because it was previously dereferenced and if it were null a null pointer exception would have occurred at the earlier dereference. We really appreciate your help. 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. PS: I also tried the code in android studio which uses Lint and got no warnings. ), NPD.CHECK.CALL.MIGHTNPD.CHECK.CALL.MUSTNPD.CHECK.MIGHTNPD.CHECK.MUSTNPD.CONST.CALLNPD.CONST.DEREFNPD.FUNC.CALL.MIGHTNPD.FUNC.CALL.MUSTNPD.FUNC.MIGHTNPD.FUNC.MUSTNPD.GEN.CALL.MIGHTNPD.GEN.CALL.MUSTNPD.GEN.MIGHTNPD.GEN.MUSTRNPD.CALLRNPD.DEREF, 45 D, 123 D, 128 D, 129 D, 130 D, 131 D, 652 S, Checks for use of null pointers (rule partially covered). But even with this, the concerned object it tagged as a possible NullPointerException problem. Reports. So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). What is a serialVersionUID and why should I use it? That interpretation of the standard is not supported universally. Dereferencing a null pointer is undefined behavior. Using Kolmogorov complexity to measure difficulty of problems? Dereferencing > this null pointer may cause the kernel go wrong. Cause we need throw our own Runtime Exception, well-known methods wont help. SonarQube - Null Pointer Dereference Issue java simonsirak (Simon Sirak) June 14, 2018, 1:18pm 1 Hi! 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. http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html. SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. At worst, it could expose debugging information that would be useful to an attacker, or My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? We can see that at obj.run(), obj can not be null, but is pointed out by Sonar. Depending on whether the pointer is valid (i.e. This is a matter of style, and also following code walkthrough. sonarlint, sonarLint (3.2.) . How do you ensure that a red herring doesn't violate Chekhov's gun? What does it mean that a reference must refer to an object, not a dereferenced null pointer? The solution that I recommend is not work with null returns or variables on Java, try to avoid it. How can this new ban on drag possibly be considered constitutional? In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. 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. At worst, it could expose debugging information that would be useful to an attacker or it could allow an That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. How do you ensure that a red herring doesn't violate Chekhov's gun? Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. 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.) Styling contours by colour and by line thickness in QGIS. https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx to non-modifiable storage when the corresponding parameter is not const-qualified) or a type (after default argument promotion) not expected by a function with a variable number of arguments, the behavior is undefined. Doing so will at best cause abrupt program termination, without the 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. To learn more, see our tips on writing great answers. Off by one error: It is the third example. On many platforms, dereferencing a null pointer results in abnormal program termination, but this is not required by the standard. It also uses the unsigned type size_t to pass the length parameter, ensuring that negative values are not passed to func(). What is null pointer exception in android. How to deal with "java.lang.OutOfMemoryError: Java heap space" error? Explain about call by reference with an . The alert is related to the sonar rule : Null pointers should not be dereferenced. 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. If you preorder a special airline meal (e.g. void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. Hi Andreas, Thanks for the feedback. In C/C++ speak, 'dereferencing' simply means getting the object that a pointer . Thered be huge value in jumping onto the latest version of the ecosystem (notably SonarQube), and benefit from all latest analyzers (e.g. java 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). 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. Please explain: Without this, we wont be able to help you. I've changed it to say null pointer instead of invalid pointer. Thanks for contributing an answer to Stack Overflow! rev2023.3.3.43278. 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. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. . But passing 0 to memcpy() is not one of them. 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). In the complaint version, I like to make source code checking a little quicker by putting parenthesizes around arguments to |= or &= as. 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. If you call connect() function, it better do the connection, but failing simply because some ptr is NULL is not good behaviour -- failures should . Thus we should check > this kstrdup() operation. However there is no portable way to verify that the pointer is valid, other than checking for null.

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