null pointers should not be dereferenced

ncdu: What's going on with this second size column? If you write [ref], then a null pointer is not allowed, but if you write [unique], then a null pointer is permitted. 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. Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. In order to fix this, just do the following: BodyType body=res.getBody (); if (body == null || body.getServiceResult () == null) { return; } You can then even reuse body after that. The article easily misleads the reader into believeing that ensuring pointer validity boils down to checking for pointer being not equal to NULL. When and how should I use a ThreadLocal variable? Connect and share knowledge within a single location that is structured and easy to search. How handle the initialization of "responseDto" without "null" because is throwing the issue on sonar. Phew, we're agreed here. 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. Making statements based on opinion; back them up with references or personal experience. That is, sets equivalent to a proper subset via an all-structure-preserving bijection. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. But even with this, the concerned object it tagged as a possible NullPointerException problem. In order to fix this, just do the following: If you are absolutely sure that res.getBody() stays null and is also not modified by another thread, you could also use a //NOSONAR comment in order to suppress the warning. NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . The correct idiom is to only allocate storage if the pointer is currently NULL. All rights are expressly reserved. Key here (explains table format and definitions), EXP34-C = Union( CWE-690, list) where list =. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). This issues is displayed by SonarQube. assert(!invalid(p)); // or whatever, bool invalid(const void *p) { 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. Avoid Returning null from Methods. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) As a result, this noncompliant code example is vulnerable to a null pointer dereference exploit, because null pointer dereferencing can be permitted on several platforms, for example, by using mmap(2) with the MAP_FIXED flag on Linux and Mac OS X, or by using the shmat() POSIX function with the SHM_RND flag [Liu 2009]. specifies the length of the array for a function. very old code or C code being worked into c++ may have functions that expect the user to delete the data. 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). 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 . 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. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. validated for null in your method declaration with it: 2008-2023 SonarSource S.A., Switzerland. I reordered that code example to do all the checks before allocations. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. 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). Does it just mean failing to correctly check if a value is null? Dereferencing a null pointer is undefined behavior, typically abnormal program termination. Aaron:I suspect we are talking past each other. Check whether a String is not Null and not Empty. So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). In the complaint version, I like to make source code checking a little quicker by putting parenthesizes around arguments to |= or &= as. @Tibor SonarQube version 5.6.6, IntelliJ SonarLint plugin 3.0.0.2041, Sonar: Null pointers should not be dereferenced, How Intuit democratizes AI development across teams through reusability. That's true. Mutually exclusive execution using std::atomic? static-code-analysis Thanks for contributing an answer to Stack Overflow! Your assertion is not backed by the wording in the standard, nor by common implementer understanding. After that, you call res.getBody() again. It could be non-null the first time but not the second time, sonar does not know this. 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. Here is our source code: Sign in to download full-size image How to tell which packages are held back due to phased updates. 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. It looks like a logic bug, which can cause a memory leaking. Note that it doesn't know how to check for non-heap, non-stack. vegan) just to try it, does this inconvenience the caterers and staff? This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. () How to use Slater Type Orbitals as a basis functions in matrix method correctly? 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). Pittsburgh, PA 15213-2612 Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? What are the effects of exceptions on performance in Java? However, memory allocation > functions such as kstrdup() may fail and returns NULL. Is there a proper earth ground point in this switch box? attacker to bypass security measures. This rule applies to all null pointers, regardless of which function returned them. Possible fix: Assign a valid address to the pointer in all branches of the conditional statement.. Pointer can point to dynamically allocated memory. 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. It could be non-null the first time but not the second time, sonar does not know this. Null pointers should not be dereferenced. 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>. SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. The problem is that something like %*pbl which reads a bitmask, will save the pointer to the bitmask in the buffer. Im very new to sonar, is there a way to add methods to the whitelist? You need to benchmark. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Issues Components. And if there is no pointer_default declaration, then the default default is ref. Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. All rights are expressly reserved. I'd guess WG14 has considered these questions, but I haven't until now :). which version of SonarQube are you using? What does it mean that a reference must refer to an object, not a dereferenced null pointer? Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. 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. I'd guess null pointers are not valid, even though they point to 0 bytes. positive S2637 in SonarQube 6.7.1 LTS, SonarQube for MSBuild not reporting quality issues, getTextContent() through "Null pointers should not be dereferenced". So Bar might not be initialized but then the last line of your example should not be evaluated in this case. Trying to understand how to get this basic Fourier Series. How can we prove that the supernatural or paranormal doesn't exist? 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. Java Specification Participation Agreement version in use: 2.0. With their flexibility, void pointers also bring some constraints. LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. Please direct comments on this JSR to the Spec Lead (s) Team. IMHO, the rule title should be changed to something less general. 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. Obviously the value of that pointer could have changed since the . While the engine is in practice already able to explore code from other files if needed (relying solely on bytecode), we restrain this approach to a limited set of well-known methods from standard libraries, for which we know that behaviors are correctly produced. It does not point to any area of memory. ), 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). Doing so will cause a NullReferenceException to be thrown. 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" Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? Dereferencing a null pointer is undefined behavior. Im currently using SonarQube version 5.6.6. better way to handle this is to store the result of method invocation in a variable. The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. When a variable is declared as being a pointer to type void, it is known as a generic pointer. Does Counterspell prevent from any further spells being cast on a given turn? 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. We resolved it by adding our tools path in the white list, and repackaging it. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 3.7. 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. If malloc() fails, it returns a null pointer that is assigned to c_str. The approximation of the try catch flow is such that we consider an exception can be thrown just after the curly brace of the try. I have a sonar alert on this call minRating.getRatgCaam(). A pointer is simply a variable that contains a memory address. If copying takes place between objects that overlap, the behavior is undefined. NullPointerException is a RuntimeException. But passing 0 to memcpy() is not one of them. Calls to extension methods are not reported because they can still operate on null values. res.getBody() == null || res.getBody().getServiceResult() == null). Does a summoned creature play immediately after being summoned by a ready action? Styling contours by colour and by line thickness in QGIS. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 1 Answer Sorted by: 1 Your code is ok. public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . 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). (C11, S7.24.2.1). Powered by Discourse, best viewed with JavaScript enabled. )}"); 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. To learn more, see our tips on writing great answers. rev2023.3.3.43278. What does "Could not find or load main class" mean? The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. 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. Then we hit memcpy with length 0. best, such an exception will cause abrupt program termination. Carnegie Mellon University What sort of strategies would a medieval military use against a fantasy giant? Status: Dormant. What is a serialVersionUID and why should I use it? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. Does Java have support for multiline strings? 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). What is the point of Thrower's Bandolier? What methods/tools can be used to determine the cause so that you stop the exception from causing the progra. The user_data pointer could be invalid in other ways, such as pointing to freed memory. How can we let this pass? It is generally accepted that zeroing a pointer is a good way to mark it as invalid and dereferencing an invalid pointer is a bug. Whats the grammar of "For those whose stories they are"? 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 it could allow an attacker to bypass security measures. Seems the analizer don't recognice the logic with the funcional object Optional. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. And fwstr > is dereferenced in the following codes. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? // <------- reported violation: NullPointerException might be thrown as 'bar' is nullable here, https://jira.sonarsource.com/browse/SONARJAVA-1490, https://groups.google.com/d/msgid/sonarqube/4752a999-246e-42c2-bbdc-8a44a5564ce9%40googlegroups.com. rev2023.3.3.43278. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. 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 The solution that I recommend is not work with null returns or variables on Java, try to avoid it. Passing ownership of something also requires pointers. Description The program can potentially dereference a null pointer, thereby raising a NullPointerException. Thanks for your relpy. Batch split images vertically in half, sequentially numbering the output files, Recovering from a blunder I made while emailing a professor. All content is copyright protected. (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). Alternate Terms Relationships It's still illegal. I would also guess that pointers that point to the one-past-the-end of an array are also invalid. A reference to Nothing should never be dereferenced/accessed. raiseException() return, Sonar An awesome tip to avoid NPE is to return empty strings or empty collections rather than null. Trying to understand how to get this basic Fourier Series. Is it possible to create a concave light? Ah, gotcha. That makes sense. SonarJava Version 5.9.2 (build 16552). 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 there a single-word adjective for "having exceptionally strong moral principles"? "After the incident", I started to be more careful not to trip over things. 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. Shouldn't the function check all pointers before dereferencing them or passing them to another function? rev2023.3.3.43278. For example the following program doesn't compile. 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. (/). To learn more, see our tips on writing great answers. 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.) 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. What is pointed to should only be deleted if it was created with new. To create a custom null validation method declare an attribute with name ValidatedNotNullAttribute and mark the parameter that is What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? What is a NullPointerException, and how do I fix it?,What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? That interpretation of the standard is not supported universally. It is still a pointer though, to use it you just have to cast it to another kind of pointer first. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. sonarlint, sonarLint (3.2.) Now, you can find the list of whitelisted methods here. Can I tell police to wait and call a lawyer when served with a search warrant? 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. But when length of A is 1, the control never reaches the else block. When B is null, The control reaches inside the main if block only when length of A is 1. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? sonarLint (3.2.) Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. But no where in that particular idiom would a NULL pointer necessarily be deferenced. positive S2637 in SonarQube 6.7.1 LTS, Sonar false positive, "change condition so that it does not always evaluate to true. NULL vs Uninitialized pointer - An uninitialized pointer stores an undefined value. Software project. We cannot understand how there could be a null pointer exception at the reported line. 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. Which version of SonarJava plugin do you have? Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. 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 Is there a single-word adjective for "having exceptionally strong moral principles"? isEmpty(Map map) http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html. 2008-2023 SonarSource S.A., Switzerland. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. You can use Optional instead. That is only true if possibleNumbers contains no element.. BTW: none of these warnings are shown by . Is a PhD visitor considered as a visiting scholar? Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. A NULL pointer can be dereferenced when signatures are being verified on PKCS7 signed or signedAndEnveloped data. We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); This is indeed an obvious False Positive from the rule. Using platform-specific means (e.g. The final NCCE is actually more insidious than it seems at first. return p == NULL || (char *)p < &_etext; Instead use String.valueOf (object). 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. Made code more compliant with other rules. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. 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. 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. Is it possible to create a concave light? Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). The alert is related to the sonar rule : Null pointers should not be dereferenced. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This code also violates ERR33-C. Detect and handle standard library errors. And the semantics, as I said, are different. Dereferencing a null pointer can lead to a denial of service. The result of calling such a helper function should be . This likely means that youre on an ancient version of the Java analyzer. 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. 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. 1 Null pointers should not be dereferenced @CheckForNull String getName(){.} that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. Why are physically impossible and logically impossible concepts considered separate in terms of probability? sonarqube I feel my situation is not as complicated. The expected result here is solve the issue with sonarqube. 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. Ticket opened : Thanks a lot for the minimalized reproducer ! How can we prove that the supernatural or paranormal doesn't exist? How can this new ban on drag possibly be considered constitutional? Trying to understand how to get this basic Fourier Series. When length is zero, it is probably unusable condition for this function. 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. Why do academics stay as adjuncts for years rather than move around? Just because something is a pointer does not mean you should call delete . Asking for help, clarification, or responding to other answers. context.RaiseException . When I added the not null validation as sonar suggest. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). It also adds assertions to document that certain other pointers must not be null. The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. Do "superinfinite" sets exist? 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. 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. Reports. In the simplest case, this function just returns the result of calling kmalloc. Recovering from a blunder I made while emailing a professor. Why does Mister Mxyzptlk need to have a weakness in the comics? Im having trouble understanding your problem. JCP version in use: 2.6.