I suppose there is a question of "Is a pointer that points to 0 bytes valid?" 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. Note that it doesn't know how to check for non-heap, non-stack. SonarJava Version 5.9.2 (build 16552). Can you please start a new thread and be more explicit about the issue you are observing. Mutually exclusive execution using std::atomic? java 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. What is null pointer exception in android. 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. Can I tell police to wait and call a lawyer when served with a search warrant? 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. EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. Whats the grammar of "For those whose stories they are"? IMHO, the rule title should be changed to something less general. A bug can cause them never to be reassigned. And if there is no pointer_default declaration, then the default default is ref. 4. sonarqube To learn more, see our tips on writing great answers. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. That is only true if possibleNumbers contains no element.. BTW: none of these warnings are shown by . 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. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. . Null pointer should not be dereferenced , io.NotSerializableException : java. Not the answer you're looking for? 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. Thanks for contributing an answer to Stack Overflow! The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. When a variable is declared as being a pointer to type void, it is known as a generic pointer. As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. I guess you could write a proposal to modify the C Standard, but our coding standard is meant to provide guidance for the existing language. Off by one error: It is the third example. I've changed it to say null pointer instead of invalid pointer. Such long getter chains can also be replaced with Optional + map + ifPresent lambda style. Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). Hi Andreas, Thanks for the feedback. The problem is that something like %*pbl which reads a bitmask, will save the pointer to the bitmask in the buffer. Why do academics stay as adjuncts for years rather than move around? If copying takes place between objects that overlap, the behavior is undefined. Thanks for contributing an answer to Stack Overflow! Made code more compliant with other rules. How to use java.net.URLConnection to fire and handle HTTP requests, Why should Java 8's Optional not be used in arguments, sonarLint complains "Null pointers should not be dereferenced (squid:S2259)" despite that possibility being handled. My below code where I'm calling a stored procedure is giving a null pointer exception. What sort of strategies would a medieval military use against a fantasy giant? Reports. The issue arises when dereferenced pointers are used. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. specifies the length of the array for a function. Much like dereferencing a dangling (or wild) pointer leads to undefined behavior, dereferencing a null pointer also leads to undefined behavior. Null pointer should not be dereferenced . best, such an exception will cause abrupt program termination. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. Good question! 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). 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. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. At this point we define size as strlen(input_str) + 1. 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. When and how should I use a ThreadLocal variable? 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. When B is null, The control reaches inside the main if block only when length of A is 1. One could argue that all code examples would be redundant with the first pair. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. . Dereferencing a null pointer can lead to a denial of service. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. But what exactly does it mean to "dereference a null pointer"? LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. 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). All rights are expressly reserved. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 3.7. I believe in this case, either expression would work. Depending on whether the pointer is valid (i.e. In C/C++ speak, 'dereferencing' simply means getting the object that a pointer . What is generic pointer? Connect and share knowledge within a single location that is structured and easy to search. Report False-positive / False-negative [LTS] The new SonarQube LTS is here: SONARQUBE 9.9 LTS, SonarQube - Null Pointer Dereference Issue. Why does Mister Mxyzptlk need to have a weakness in the comics? But even with this, the concerned object it tagged as a possible NullPointerException problem. Do "superinfinite" sets exist? Many platforms can support testing for those also. In the simplest case, this function just returns the result of calling kmalloc. As for copy vs pointer/reference - it depends. Trying to understand how to get this basic Fourier Series. 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. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The final NCCE is actually more insidious than it seems at first. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. SonarQube Version 6.7.2 (build 37468) This code also violates ERR33-C. Detect and handle standard library errors. Goal Software project. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This sounds indeed like a bug in the flow when an exception is raised. 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. , NPE : null-, . Instead use String.valueOf (object). Now (sonarqube java analyzer version 4.3.0.7717) it's supported and works fine. (C11, S7.24.2.1). A reference to Nothing should never be dereferenced/accessed. Finally my method is returning a response with value of restTemplate. Seems the analizer don't recognice the logic with the funcional object Optional. Check whether a String is not Null and not Empty. 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. Put a new ResponseEntity is wrong because I won't know what will be the answer for the status of http. rev2023.3.3.43278. 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. 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. 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. In the meantime, Im locking this thread. Appropriate typecasting is necessary. Here is our source code: Sign in to download full-size image That interpretation of the standard is not supported universally. 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. To learn more, see our tips on writing great answers. 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>. We can get a reference to point to null in the following ways: "uninitialized" reference type variables variables which are initialized with nulls and are assigned their real value afterward. Thank you for clarifying your assertion until I understood it properly. This compliant solution ensures that the pointer returned by png_malloc() is not null. I'd guess WG14 has considered these questions, but I haven't until now :). Is the God of a monotheism necessarily omnipotent? Dereferencing a null pointer results in undefined behavior. Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. 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 Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. Is there a single-word adjective for "having exceptionally strong moral principles"? SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. Share Improve this answer Follow answered Oct 5, 2017 at 16:27 This is a matter of style, and also following code walkthrough. Thus we should check > this kstrdup() operation. [4] Trying to understand how to get this basic Fourier Series. 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. Making statements based on opinion; back them up with references or personal experience. 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. Does Java have support for multiline strings? This code also violates ERR33-C. Detect and handle standard library errors. If you say [in] or [out] without a modifier, then the modifier defaults to the pointer_default for the enclosing class. Im very new to sonar, is there a way to add methods to the whitelist? This topic was automatically closed 7 days after the last reply. 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. 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. Is the God of a monotheism necessarily omnipotent? () 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]. A pointer is simply a variable that contains a memory address. Why are physically impossible and logically impossible concepts considered separate in terms of probability? When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. So the SIZE_MAX check was unnecessary. In C# and Java, all reference types can point to null. The user_data pointer could be invalid in other ways, such as pointing to freed memory. context.RaiseException , (/) Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. My question is; is my solution incorrect? If you try to access any member variables or methods with that variable, you are trying to dereference it. 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 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 approximation of the try catch flow is such that we consider an exception can be thrown just after the curly brace of the try. 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. public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . The same problem we will have with "Add at least one assertion to this test case." For the time being, I would unfortunately recommend to mark as False Positive the issue. Trying to understand how to get this basic Fourier Series. SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. Software project. Null pointers should not be dereferenced. The method isNR (minRating) is a helper method that validate among other things, if the object minRating is null public boolean isNR (AgencyRating rating) { return rating == null || isNR (rating.getRatgCaam ()); } When I added the not null validation as sonar suggest. Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. At worst, it could expose debugging information that would be useful to an attacker, or Are there tables of wastage rates for different fruit and veg? 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. Aaron:I suspect we are talking past each other. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. At Is it possible to create a concave light? Not the answer you're looking for? If you write [ref], then a null pointer is not allowed, but if you write [unique], then a null pointer is permitted. You can use Optional instead. These can be: Invoking a method from a null object. I feel my situation is not as complicated. 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 there a proper earth ground point in this switch box? 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. How to use Slater Type Orbitals as a basis functions in matrix method correctly? the Java one). 2008-2023 SonarSource S.A., Switzerland. Identify where the allocation occurs. We. - the incident has nothing to do with me; can I use this this way? Solution 1, it looks like, today's solution tomorrow's problem. Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. Is there a single-word adjective for "having exceptionally strong moral principles"? Thanks, David! 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). (from res.getBody().getServiceResult() ). rev2023.3.3.43278. 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. it could allow an attacker to bypass security measures. 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 . 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. can have the value zero on a call to that function. Recovering from a blunder I made while emailing a professor. extern char _etext; Now, you can find the list of whitelisted methods here. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. https://stackoverflow.com/questions/47534436/, https://stackoverflow.com/questions/47534436/, java - Jenkins groovy : Error: java. 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. ii. 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 issue of passing n=0 to memcpy() is distinct from null or invalid pointers. Phew, we're agreed here. When exploring such methods, the engine then deduces behaviors regarding null-checking (among other things). Trying to understand how to get this basic Fourier Series. The correct idiom is to only allocate storage if the pointer is currently NULL. And the semantics, as I said, are different. )}"); In this case, the difference is the assumption thatmalloc() always returns non-nullfor the second NCCE, whereas the first NCCE has themalloc() abstracted away. Just a few words about the rule now. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). Optimizers are optimizing based on this latitude and have been for years. which would allow us to systematically observe what you are having. Linear regulator thermal information missing in datasheet, Identify those arcade games from a 1983 Brazilian music video. Is null check needed before calling instanceof? 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. 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! Why does the second compliant example permit using possibly-null pointers? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. This rule applies to all null pointers, regardless of which function returned them. I have checked on multiple . The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. }. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) What methods/tools can be used to determine the cause so that you stop the exception from causing the progra. Not the answer you're looking for? Hi @Michael! sonarLint (3.2.) Asking for help, clarification, or responding to other answers. There is no guarantee that subsequent invocations are returning the same value, thats why issue is raised. ability to run any cleanup processes. Some Interesting Facts: 1) void pointers cannot be dereferenced. PS: I also tried the code in android studio which uses Lint and got no warnings. Extended Description NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. static-code-analysis In case the hash algorithm used for the signature is known to the OpenSSL library but the implementation of the hash algorithm is not available the digest initialization will fail. rev2023.3.3.43278. I suggest that this topic needs to include calloc() and realloc() Refer to Linux man pages online for more enlightenment about malloc(), and friends. Hello. This issues is displayed by SonarQube. C# static code analysis: Null pointers should not be dereferenced Products In-IDE IDE extension that lets you fix coding issues before they exist! isEmpty(Map map) Believing that dereferencing NULL shouldn't crash the system doesn't make it true. All content is copyright protected. ", 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". How do I align things in the following tabular environment? 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 Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. Obviously the value of that pointer could have changed since the . 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. Your assertion is not backed by the wording in the standard, nor by common implementer understanding. 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. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. Thered be huge value in jumping onto the latest version of the ecosystem (notably SonarQube), and benefit from all latest analyzers (e.g. Asking for help, clarification, or responding to other answers.
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