null pointers should not be dereferenced

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. NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. The alert is related to the sonar rule : Null pointers should not be dereferenced. Just a few words about the rule now. Is the God of a monotheism necessarily omnipotent? What sort of strategies would a medieval military use against a fantasy giant? Accessing or modifying a null object's field. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); Whoops, you're right. Finally my method is returning a response with value of restTemplate. Find centralized, trusted content and collaborate around the technologies you use most. Avoid Returning null from Methods. 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 Which version of SonarJava plugin do you have? Thanks for the feedback. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. Since you cannot have a variable of type void, the pointer will not point to any data and therefore cannot be dereferenced. See "Clever Attack Exploits Fully-Patched Linux Kernel" [Goodin 2009] for an example of a code execution exploit that resulted from a null pointer dereference. I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. Why are physically impossible and logically impossible concepts considered separate in terms of probability? Write a semantic patch to nd cases where the result of calling kmalloc is dereferenced with no previous NULL pointer test. Ah, gotcha. It also adds assertions to document that certain other pointers must not be null. It also reinforces the notion to the reader that any time you see arithmetic in an allocation expression, you need to think about corner-cases. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Sonar: Null pointers should not be dereferenced, Why should Java 8's Optional not be used in arguments, Sonar alert : "private" methods that don't access instance data should be "static", sonarLint complains "Null pointers should not be dereferenced (squid:S2259)" despite that possibility being handled, Java: (false?) [4] Is there a single-word adjective for "having exceptionally strong moral principles"? Made code more compliant with other rules. However, memory allocation > functions such as kstrdup() may fail and returns NULL. ), 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. By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. If the project is not compiled, and without sonar.java.binaries whether the white list takes effect? Asking for help, clarification, or responding to other answers. I don't need to do this validation again. These can be: Invoking a method from a null object. I'd guess WG14 has considered these questions, but I haven't until now :). That is only true if possibleNumbers contains no element.. BTW: none of these warnings are shown by . 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. Why is there a voltage on my HDMI and coaxial cables? 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. In the meantime, Im locking this thread. Dereferencing > this null pointer may cause the kernel go wrong. The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. SonarJava Version 5.9.2 (build 16552). Dereferencing a null pointer can lead to a denial of service. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. In Java, a special null value can be assigned to an object reference. On many platforms, dereferencing a null pointer results inabnormal program termination, but this is not required by the standard. You do not have permission to delete messages in this group, Either email addresses are anonymous for this group or you need the view member email addresses permission to view the original message. res.getBody() == null || res.getBody().getServiceResult() == null). Trying to understand how to get this basic Fourier Series. Whats the grammar of "For those whose stories they are"? But when length of A is 1, the control never reaches the else block. Doing so will cause a NullPointerException to be thrown. If malloc() fails, it returns a null pointer that is assigned to c_str. The final NCCE is actually more insidious than it seems at first. points to memory allocated to the process) and what exactly was allocated there after the public key was freed, this may cause a segmentation fault or even execute code, which could again cause a segmentation fault, but might potentially be under the attacker's control. minimal code sample to reproduce (with analysis parameter, and potential instructions to compile). Shouldn't the function check all pointers before dereferencing them or passing them to another function? Solution 1, it looks like, today's solution tomorrow's problem. Powered by Discourse, best viewed with JavaScript enabled. 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. Put a new ResponseEntity is wrong because I won't know what will be the answer for the status of http. {"serverDuration": 214, "requestCorrelationId": "084acdc104f21c51"}, EXP34-C. Do not dereference null pointers, Clever Attack Exploits Fully-Patched Linux Kernel, ERR33-C. Detect and handle standard library errors, one compliant and one non-compliant example, CERT Oracle Secure Coding Standard for Java, EXP01-J. For the time being, I would unfortunately recommend to mark as False Positive the issue. But passing 0 to memcpy() is not one of them. 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. That interpretation of the standard is not supported universally. I suppose there is a question of "Is a pointer that points to 0 bytes valid?" . 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 After that, you call res.getBody() again. Calls to extension methods are not reported because they can still operate on null values. 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). Identify where the allocation occurs. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. isEmpty(Map map) A pointer to null (the 0 memory address) should never be dereferenced/accessed. On such a call, a function that locates a character finds no occurrence, a function that compares two character sequences returns zero, and a function that copies characters copies zero characters. ", 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". Thanks, David! 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). Alternate Terms Relationships 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 . Explain about call by reference with an . 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 approximation of the try catch flow is such that we consider an exception can be thrown just after the curly brace of the try. If not, this might be a bug. Correct; a null pointer is not a valid pointer for the C library functions. An awesome tip to avoid NPE is to return empty strings or empty collections rather than null. Off by one error: It is the third example. Hi Andreas, Thanks for the feedback. The correct idiom is to only allocate storage if the pointer is currently NULL. Sonar is ok. Sonar can't determine that the helper method did the null validation. There are other problems with this code, as is noted in the rule. Does Counterspell prevent from any further spells being cast on a given turn? In particular, ROSE ensures that any pointer returned by malloc(), calloc(), or realloc() is first checked for NULL before being used (otherwise, it is free()-ed). "After the incident", I started to be more careful not to trip over things. We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. 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. . At best, such an exception will cause abrupt program termination. Why does Mister Mxyzptlk need to have a weakness in the comics? IMHO, the rule title should be changed to something less general. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Which @NotNull Java annotation should I use? Connect and share knowledge within a single location that is structured and easy to search. Styling contours by colour and by line thickness in QGIS. Im very new to sonar, is there a way to add methods to the whitelist? 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. We can see that at obj.run(), obj can not be null, but is pointed out by Sonar. 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. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Perhaps this could be done with a special constraint that will notify the SE engine that we learned from a Debug.Assert call. (from res.getBody().getServiceResult() ). What is generic pointer? The n=0 is a mildly interesting edge case: Clearly a pointer that points to at least one valid byte could be used as the src or dest pointer to a call to memcpy(, 0). Replacing broken pins/legs on a DIP IC package, Bulk update symbol size units from mm to map units in rule-based symbology, How do you get out of a corner when plotting yourself into a corner. 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. How can we prove that the supernatural or paranormal doesn't exist? At best, such an exception will cause abrupt program termination. There are many ways to resolve this. rev2023.3.3.43278. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. It's still illegal. This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Can I tell police to wait and call a lawyer when served with a search warrant? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Things go fine now. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. When B is null, The control reaches inside the main if block only when length of A is 1. Dereferencing a null pointer results in undefined behavior. public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . 4. it could allow an attacker to bypass security measures. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) 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?) The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. Is it possible to create a concave light? Doing so will cause a NullReferenceException to be thrown. For example the following program doesn't compile. How can we let this pass? I have a sonar alert on this call minRating.getRatgCaam(). 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. - the incident has nothing to do with me; can I use this this way? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Now (sonarqube java analyzer version 4.3.0.7717) it's supported and works fine. Optimizers are optimizing based on this latitude and have been for years. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Two null pointers will always be equal to each other. A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. In the simplest case, this function just returns the result of calling kmalloc. null(java.lang.NullPointerException) . Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. , . At worst, it could expose debugging information that would be useful to an attacker, or 3.7. As for copy vs pointer/reference - it depends. 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 (?,?,?,?,?,?,?,? 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. We resolved it by adding our tools path in the white list, and repackaging it. I feel my situation is not as complicated. 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 . Likewise, pointers to freed memory are not valid. It does not point to any area of memory. If copying takes place between objects that overlap, the behavior is undefined. Void pointers cannot be dereferenced as any other pointer. All content is copyright protected. A NULL pointer can be dereferenced when signatures are being verified on PKCS7 signed or signedAndEnveloped data. Then we hit memcpy with length 0. One could argue that all code examples would be redundant with the first pair. If you try to access any member variables or methods with that variable, you are trying to dereference it. Please explain: Without this, we wont be able to help you. 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. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I have checked on multiple . Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. The only potential null is the return value of list(). attacker to bypass security measures. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. 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. All rights are expressly reserved. Now, you can find the list of whitelisted methods here. 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. Does a summoned creature play immediately after being summoned by a ready action? 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. 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. specifies the length of the array for a function. 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. . This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. - the incident has nothing to do with me; can I use this this way? That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. 4500 Fifth Avenue 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. This is indeed an obvious False Positive from the rule. NullPointerException is a RuntimeException. It also uses the unsigned type size_t to pass the length parameter, ensuring that negative values are not passed to func(). 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. In the code, we check the not nullity with java.util.Objects.nonNull(). IDE extension that lets you fix coding issues before they exist! uninitialized reference-type class members. Is there a proper earth ground point in this switch box? The result of calling such a helper function should be . False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. How to deal with "java.lang.OutOfMemoryError: Java heap space" error? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, SonarQube null pointers should not be dereferenced on try/catch, How Intuit democratizes AI development across teams through reusability. Note that it doesn't know how to check for non-heap, non-stack. NullPointerException is thrown when program attempts to use an object reference that has the null value. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. It means this is illegal: T* p = nullptr; T& r = *p; // illegal NOTE: Please do not email us saying the above works on your particular version of your particular compiler. How can this new ban on drag possibly be considered constitutional? This code also violates ERR33-C. Detect and handle standard library errors. What methods/tools can be used to determine the cause so that you stop the exception from causing the progra. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, It is a false positive, but it might be a good idea not to do the, Sonar false-positive on rule: Null pointers should not be dereferenced, How Intuit democratizes AI development across teams through reusability. SonarQube Version 6.7.2 (build 37468) Software project. Description The program can potentially dereference a null pointer, thereby raising a NullPointerException. I reordered that code example to do all the checks before allocations. A reference to null should never be dereferenced/accessed. When a variable is declared as being a pointer to type void, it is known as a generic pointer. Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. 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 the pointer returned by png_malloc() is not null. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. in above code, Asking for help, clarification, or responding to other answers. What is a serialVersionUID and why should I use it? sonarLint (3.2.) To learn more, see our tips on writing great answers. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . which version of SonarQube are you using? SonarLint IntelliJ 4.0.0.2916 Java Rule 'Null pointers should not be dereferenced' I'm getting this fault in the next code when obj can't be null in any scenario. Best to cite C11 s7.24.2.1 here: The memcpy function copies n characters from the object pointed to by s2 into the object pointed to by s1. A 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. It is still a pointer though, to use it you just have to cast it to another kind of pointer first. SonarLint: A "NullPointerException" could be thrown; "getBody()" can return null. 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.) What does "Could not find or load main class" mean? Provide a self-contained reproducer (zipped project?) 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. The user_data pointer could be invalid in other ways, such as pointing to freed memory. To learn more, see our tips on writing great answers. In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. java 1 Answer Sorted by: 2 Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? Interactions/interfaces with C can't use references. We cannot understand how there could be a null pointer exception at the reported line. Im currently using SonarQube version 5.6.6. better way to handle this is to store the result of method invocation in a variable. Software project. This topic was automatically closed 7 days after the last reply. I suggest that this topic needs to include calloc() and realloc() Refer to Linux man pages online for more enlightenment about malloc(), and friends. 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(). It's a modular system with the . best, such an exception will cause abrupt program termination. 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. Not the answer you're looking for? Connect and share knowledge within a single location that is structured and easy to search. Thanks for contributing an answer to Stack Overflow! 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. So we have to check all the arguments before performing any actions. the Java one). Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. 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. At worst, it could expose debugging information that would be useful to an attacker or it could allow an I believe in this case, either expression would work.