This solution also ensures that theuser_data pointer is not null. . Goal Unfortunately, its actual state also has some limitations, like the one you are hitting here. Can you please start a new thread and be more explicit about the issue you are observing. At this point we define size as strlen(input_str) + 1. 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. Cause we need throw our own Runtime Exception, well-known methods wont help. 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. Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. And the semantics, as I said, are different. When you have a variable of non-primitive type, it is a reference to an object. Can I tell police to wait and call a lawyer when served with a search warrant? Does a summoned creature play immediately after being summoned by a ready action? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. versions used (SonarQube, Scanner, language analyzer) Thered be huge value in jumping onto the latest version of the ecosystem (notably SonarQube), and benefit from all latest analyzers (e.g. assert(!invalid(p)); // or whatever, bool invalid(const void *p) { 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]. Reports. Not the answer you're looking for? I have checked on multiple . But what exactly does it mean to "dereference a null pointer"? How can we prove that the supernatural or paranormal doesn't exist? Which @NotNull Java annotation should I use? Thanks for contributing an answer to Stack Overflow! So Bar might not be initialized but then the last line of your example should not be evaluated in this case. Using Kolmogorov complexity to measure difficulty of problems? Dereferencing a null pointer results in undefined behavior. 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. Believing that dereferencing NULL shouldn't crash the system doesn't make it true. This code also violates ERR33-C. Detect and handle standard library errors. 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. IMHO, the rule title should be changed to something less general. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. Depending on whether the pointer is valid (i.e. 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. I added a comment to explain that SIZE_MAX is the limit of size_t. 11 Sep, 2006. which would allow us to systematically observe what you are having. There are many ways to resolve this. Hi @Michael! Just a few words about the rule now. This is indeed an obvious False Positive from the rule. Is it possible to rotate a window 90 degrees if it has the same length and width? What is generic pointer? As for copy vs pointer/reference - it depends. Reports. Just because something is a pointer does not mean you should call delete . I am a student implementing stack with singly linked list using C, following a book called Fundamentals of Data Structures in C.. I'd guess null pointers are not valid, even though they point to 0 bytes. best, such an exception will cause abrupt program termination. I have a sonar alert on this call minRating.getRatgCaam(). isEmpty(Collection collection) Provide a self-contained reproducer (zipped project?) 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(). Why does the second compliant example permit using possibly-null pointers? Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. This topic was automatically closed 7 days after the last reply. All content is copyright protected. As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. specifies the length of the array for a function. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. This sounds indeed like a bug in the flow when an exception is raised. You can compare a pointer with NULL to test for the special condition. How do I align things in the following tabular environment? Is there a single-word adjective for "having exceptionally strong moral principles"? In C, dereferencing a null pointer is undefined behavior. the Java one). 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. The method isNR(minRating) is a helper method that validate among other things, if the object minRating is null. 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. When a variable is declared as being a pointer to type void, it is known as a generic pointer. rev2023.3.3.43278. So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . How can I check before my flight that the cloud separation requirements in VFR flight rules are met? 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. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? 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. I believe in this case, either expression would work. In the code, we check the not nullity with java.util.Objects.nonNull(). Dereferencing a null pointer can lead to a denial of service. Such long getter chains can also be replaced with Optional + map + ifPresent lambda style. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures. When exploring such methods, the engine then deduces behaviors regarding null-checking (among other things). I'd guess WG14 has considered these questions, but I haven't until now :). Is there a proper earth ground point in this switch box? 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. At But when length of A is 1, the control never reaches the else block. Thus we should check > this kstrdup() operation. There is a missing check for the return value from . Calls to extension methods are not reported because they can still operate on null values. It also uses the unsigned type size_t to pass the length parameter, ensuring that negative values are not passed to func(). My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? The only potential null is the return value of list(). A bug can cause them never to be reassigned. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Does it just mean failing to correctly check if a value is null? I suggest that this topic needs to include calloc() and realloc() Refer to Linux man pages online for more enlightenment about malloc(), and friends. Rule squid:S2259 is based on a Symbolic Execution (SE) engine. The SonarJava SE engine is however, by default, not configured to explore methods declared in other files (in your case, your utility class CheckUtils). 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. Agreed. Does Counterspell prevent from any further spells being cast on a given turn? We can see that at obj.run(), obj can not be null, but is pointed out by Sonar. Appropriate typecasting is necessary. Im very new to sonar, is there a way to add methods to the whitelist? This compliant solution ensures that the pointer returned by png_malloc() is not null. However there is no portable way to verify that the pointer is valid, other than checking for null. Why are physically impossible and logically impossible concepts considered separate in terms of probability? uninitialized reference-type class members. 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. very old code or C code being worked into c++ may have functions that expect the user to delete the data. I could've fixed this by changing else to else if (B != null && B.length == 1), but doing so rewards me with warning "condition(B != null && B.length == 1) is always true". Doing so will cause a NullPointerException to be thrown. If you say [in] or [out] without a modifier, then the modifier defaults to the pointer_default for the enclosing class. - the incident has nothing to do with me; can I use this this way? Using Kolmogorov complexity to measure difficulty of problems? The null pointer check for writing or dereferencing should be a compiler flag or library setting. The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. You need to benchmark. Styling contours by colour and by line thickness in QGIS. Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). IDE extension that lets you fix coding issues before they exist! , . That interpretation of the standard is not supported universally. attacker to bypass security measures. You can use Optional instead. Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. . Put a new ResponseEntity is wrong because I won't know what will be the answer for the status of http. Finally my method is returning a response with value of restTemplate. What is a NullPointerException, and how do I fix it?,What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? SIZE_MAX is the largest possible value that a size_t could take, so it is not possible to have anything larger than SIZE_MAX. 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. Made code more compliant with other rules. io.NotSerializableException : java. Shouldn't the function check all pointers before dereferencing them or passing them to another function? Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? The solution that I recommend is not work with null returns or variables on Java, try to avoid it. I say "theoretical" because I have not successfully produced strings of this length in testing. 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. 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. Recovering from a blunder I made while emailing a professor. Unlike reference types, pointer types are not tracked by the default garbage . Thanks for the feedback. If malloc() fails, it returns a null pointer that is assigned to c_str. 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. 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). This cross-file approach analysis can be quite resource-consuming, and we are not ready to openly enable the feature. The correct idiom is to only allocate storage if the pointer is currently NULL. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). If copying takes place between objects that overlap, the behavior is undefined. 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. Things go fine now. The result of calling such a helper function should be . Not the answer you're looking for? sonarLint (3.2.) This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. Dereferencing a null pointer is undefined behavior. positive S2637 in SonarQube 6.7.1 LTS, SonarQube for MSBuild not reporting quality issues, getTextContent() through "Null pointers should not be dereferenced". Dereferencing > this null pointer may cause the kernel go wrong. Making statements based on opinion; back them up with references or personal experience. Find centralized, trusted content and collaborate around the technologies you use most. 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. Pittsburgh, PA 15213-2612 Minimising the environmental effects of my dyson brain. To create a custom null validation method declare an attribute with name ValidatedNotNullAttribute and mark the parameter that is Asking for help, clarification, or responding to other answers. How do I align things in the following tabular environment? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. But even with this, the concerned object it tagged as a possible NullPointerException problem. NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. 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?) Connect and share knowledge within a single location that is structured and easy to search. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. The method takes a relation name r as input, executes the query "select * from r," and prints the result out in tabular format with the attribute names displayed in the table's header; the attribute names are displayed in the table's header. EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. Issues Components. How can we let this pass? 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). Pointer members in structs are not checked. How do you ensure that a red herring doesn't violate Chekhov's gun? 3.7. The final NCCE is actually more insidious than it seems at first. With their flexibility, void pointers also bring some constraints. 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. Whoops, you're right. 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. Solution 1, it looks like, today's solution tomorrow's problem. ability to run any cleanup processes. name result . 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. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. The same problem we will have with "Add at least one assertion to this test case."
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