null pointers should not be dereferenced

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C# static code analysis: Null pointers should not be dereferenced Products In-IDE IDE extension that lets you fix coding issues before they exist! In layman's terms, a null pointer is a pointer to an address in the memory space that does not have a meaningful value and cannot be referenced by the calling program, for whatever reason. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures. In Java, a special null value can be assigned to an object reference. If the pointer is not NULL, see if the assignment occurs only in a branch of a conditional statement.Investigate when that branch does not execute. Trying to understand how to get this basic Fourier Series. Not the answer you're looking for? Doing so will at best cause abrupt program termination, without the Unlike reference types, pointer types are not tracked by the default garbage . 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. How can we let this pass? 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. We. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. What is null pointer exception in android. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. However, memory allocation > functions such as kstrdup() may fail and returns NULL. (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). My question is; is my solution incorrect? On many platforms, dereferencing a null pointer results inabnormal program termination, but this is not required by the standard. Asking for help, clarification, or responding to other answers. Appropriate typecasting is necessary. 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?) My below code where I'm calling a stored procedure is giving a null pointer exception. isEmpty(Collection collection) Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. I'd guess WG14 has considered these questions, but I haven't until now :). If not, this might be a bug. What is generic pointer? I feel my situation is not as complicated. The expected result here is solve the issue with sonarqube. - the incident has nothing to do with me; can I use this this way? It's still illegal. LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. SonarJava Version 5.9.2 (build 16552). This topic was automatically closed 7 days after the last reply. Could I capture, and I would be able to glean much security information from the dump? Good question! 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. An awesome tip to avoid NPE is to return empty strings or empty collections rather than null. The method isNR(minRating) is a helper method that validate among other things, if the object minRating is null. On many platforms, dereferencing a null pointer results in abnormal program termination, but this is not required by the standard. Pointer members in structs are not checked. rev2023.3.3.43278. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. attacker to bypass security measures. Do "superinfinite" sets 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. Provide a self-contained reproducer (zipped project?) As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. ", 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 proper earth ground point in this switch box? 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. 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. 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). Shouldn't the function check all pointers before dereferencing them or passing them to another function? Does Counterspell prevent from any further spells being cast on a given turn? Null pointers should not be dereferenced. Maybe one of these methods is already doing what your methods is doing, and could be considered as replacement. that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. At best, such an exception will cause abrupt program termination. extern char _etext; The result of calling such a helper function should be . One could argue that all code examples would be redundant with the first pair. That is why I explicitly check for this in my attempted solution. Is there a solution to add special characters from software and how to do it, Acidity of alcohols and basicity of amines. A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. 4500 Fifth Avenue A reference to null should never be dereferenced/accessed. I have checked on multiple . By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. 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. Identify where the allocation occurs. 1 Null pointers should not be dereferenced @CheckForNull String getName(){.} By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 2008-2023 SonarSource S.A., Switzerland. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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. 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 sonarlint complains that Solution 1, it looks like, today's solution tomorrow's problem. Is there a single-word adjective for "having exceptionally strong moral principles"? Not the answer you're looking for? To create a custom null validation method declare an attribute with name ValidatedNotNullAttribute and mark the parameter that is Batch split images vertically in half, sequentially numbering the output files, Recovering from a blunder I made while emailing a professor. Using Kolmogorov complexity to measure difficulty of problems? With their flexibility, void pointers also bring some constraints. Do not use a null in a case where an object is required, https://gcc.gnu.org/gcc-4.9/porting_to.html, Prior to 2018-01-12: CERT: Unspecified Relationship, Pointer Casting and Pointer Type Changes [HFC], Dereferencing an out-of-domain pointer [nullref], Section 5.2.18, "Null-Pointer Dereference", Dereferencing null pointers that were not returned by a function. 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 fact that you can't pass a null (no object) with a reference parameter can be a reason to use a pointer instead. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. In C, dereferencing a null pointer is undefined behavior. Making statements based on opinion; back them up with references or personal experience. This will normally lead to an unhandled error, resulting in a segmentation fault. Likewise, pointers to freed memory are not valid. Can I tell police to wait and call a lawyer when served with a search warrant? IMHO, the rule title should be changed to something less general. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. Why does the second compliant example permit using possibly-null pointers? Explain about call by reference with an . 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. Phew, we're agreed here. Does a summoned creature play immediately after being summoned by a ready action? 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. SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. This sounds indeed like a bug in the flow when an exception is raised. Thanks, David! For example the following program doesn't compile. I would also guess that pointers that point to the one-past-the-end of an array are also invalid. Dereferencing > this null pointer may cause the kernel go wrong. Even if the object is null in this case, it will not give an exception and will print ' null ' to the output stream. So the first execution of ValidateNumber inside the foreach works fine and valid is set to true.The second execution throws the exception and exception is set in the catch-Block.. positive S2637 in SonarQube 6.7.1 LTS, SonarQube for MSBuild not reporting quality issues, getTextContent() through "Null pointers should not be dereferenced". At worst, it could expose debugging information that would be useful to an attacker or it could allow an Made code more compliant with other rules. 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. At Connect and share knowledge within a single location that is structured and easy to search. 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. Software project. Accessing or modifying a null object's field. NullPointerException is thrown when program attempts to use an object reference that has the null value. Believing that dereferencing NULL shouldn't crash the system doesn't make it true. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Automated Detection Null pointer dereferences can happen in path-dependent ways. . 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. What sort of strategies would a medieval military use against a fantasy giant? 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. Is the God of a monotheism necessarily omnipotent? NullPointerException is a RuntimeException. )}"); That is only true if possibleNumbers contains no element.. BTW: none of these warnings are shown by . uninitialized reference-type class members. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? These can be: Invoking a method from a null object. Extended Description NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. Just because something is a pointer does not mean you should call delete . The correct idiom is to only allocate storage if the pointer is currently NULL. Minimising the environmental effects of my dyson brain. Ah, gotcha. Void pointers cannot be dereferenced as any other 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. Isn't easier just to check valid range of length? Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. IDE extension that lets you fix coding issues before they exist! Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? SonarQube Version 6.7.2 (build 37468) 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?) 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. ncdu: What's going on with this second size column? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. I am a student implementing stack with singly linked list using C, following a book called Fundamentals of Data Structures in C.. 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. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? To learn more, see our tips on writing great answers. Is there a single-word adjective for "having exceptionally strong moral principles"? This is indeed a false positive because, at time of writing, the sonarqube java analyzer (version 4.2.1 at time of writing) does not support cross procedural analysis and so it is not able to determine that indeed, for the condition to be true, the value of minRating has to be non null. , . What are the effects of exceptions on performance in Java? ), 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). 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 Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. SonarJava. Aaron:I suspect we are talking past each other. 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. (C11, S7.24.2.1). This cross-file approach analysis can be quite resource-consuming, and we are not ready to openly enable the feature. I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. PS: I also tried the code in android studio which uses Lint and got no warnings. Avoid Returning null from Methods. If you say [in] or [out] without a modifier, then the modifier defaults to the pointer_default for the enclosing class. Linear regulator thermal information missing in datasheet, Identify those arcade games from a 1983 Brazilian music video. Pittsburgh, PA 15213-2612 This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. 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. You can use Optional instead. (/). Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. java So let me be more precise in my wording: I assert that a platform whose memcpy() did anything besides copy zero bytes when given n=0 and valid src and dest pointers was not C-standards-compliant. 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. Calls to extension methods are not reported because they can still operate on null values. Not the answer you're looking for? 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. What is pointed to should only be deleted if it was created with new. This code also violates ERR33-C. Detect and handle standard library errors. Reports. Carnegie Mellon University Dereferencing a null pointer can lead to a denial of service. 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. Making statements based on opinion; back them up with references or personal experience. Why are physically impossible and logically impossible concepts considered separate in terms of probability? But when length of A is 1, the control never reaches the else block. Possible fix: Assign a valid address to the pointer in all branches of the conditional statement.. Pointer can point to dynamically allocated memory. I suggest that this topic needs to include calloc() and realloc() Refer to Linux man pages online for more enlightenment about malloc(), and friends. 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. You're in a company-managed project. How can we prove that the supernatural or paranormal doesn't exist? 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 . Key here (explains table format and definitions), EXP34-C = Union( CWE-690, list) where list =. And if there is no pointer_default declaration, then the default default is ref. Thanks for your relpy. The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. 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. Put a new ResponseEntity is wrong because I won't know what will be the answer for the status of http. 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. Which @NotNull Java annotation should I use? 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" Then we hit memcpy with length 0. - the incident has nothing to do with me; can I use this this way? Connect and share knowledge within a single location that is structured and easy to search. We might set a pointer to null even if we are not freeing a object, simply to dissociate one object from another: tty_driver->tty = NULL; /* detach low level driver from the tty device */ 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.) Many platforms can support testing for those also. You can compare a pointer with NULL to test for the special condition. It is still a pointer though, to use it you just have to cast it to another kind of pointer first. {"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. After that, you call res.getBody() again. Check whether a String is not Null and not Empty. 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! res.getBody() == null || res.getBody().getServiceResult() == null). All content is copyright protected. It could be non-null the first time but not the second time, sonar does not know this. What does it mean that a reference must refer to an object, not a dereferenced null pointer? Goal which version of SonarQube are you using? So Bar might not be initialized but then the last line of your example should not be evaluated in this case. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. There are other problems with this code, as is noted in the rule. Basically, yes. 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. Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. context.RaiseException , (/) How can this new ban on drag possibly be considered constitutional? Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null.

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