Dereferencing a null pointer results in undefined behavior. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. PDF Fourth Coccinelle Workshop { Exercises 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. Find centralized, trusted content and collaborate around the technologies you use most. In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. 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. 4. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures. 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. The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. All rights are expressly reserved. The correct idiom is to only allocate storage if the pointer is currently NULL. I'd guess null pointers are not valid, even though they point to 0 bytes. There is a missing check for the return value from . Thanks, David! Shouldn't the function check all pointers before dereferencing them or passing them to another function? Why does Mister Mxyzptlk need to have a weakness in the comics? 3.7. 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 . These can be: Invoking a method from a null object. Dereferencing a null pointer can lead to a denial of service. The expected result here is solve the issue with sonarqube. Could I capture, and I would be able to glean much security information from the dump? I added an assertion to that compliant code example. When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. This issues is displayed by SonarQube. 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. Im very new to sonar, is there a way to add methods to the whitelist? Is it possible to create a concave light? Thus we should check > this kstrdup() operation. Using Kolmogorov complexity to measure difficulty of problems? In the simplest case, this function just returns the result of calling kmalloc. And if there is no pointer_default declaration, then the default default is ref. In the meantime, Im locking this thread. If you write [ref], then a null pointer is not allowed, but if you write [unique], then a null pointer is permitted. return p == NULL || (char *)p < &_etext; What is the point of Thrower's Bandolier? And the semantics, as I said, are different. All rights are expressly reserved. The fact that you can't pass a null (no object) with a reference parameter can be a reason to use a pointer instead. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? , . 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 What is a NullPointerException, and how do I fix it?,What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? rev2023.3.3.43278. You need to benchmark. Thanks for contributing an answer to Stack Overflow! [JAVA] 3.9 - FP for S2259 Null pointers should not be dereferenced This cross-file approach analysis can be quite resource-consuming, and we are not ready to openly enable the feature. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. 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. Aaron:I suspect we are talking past each other. Share Improve this answer Follow answered Oct 5, 2017 at 16:27 rev2023.3.3.43278. please explain null pointer dereference [Solved] (Java in General forum Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. sonarlint, sonarLint (3.2.) Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? 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. References, C++ FAQ 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>. But even with this, the concerned object it tagged as a possible NullPointerException problem. NULL POINTERS SHOULD NOT BE DEREFERENCED - jobhuntley.com Asking for help, clarification, or responding to other answers. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. Why do academics stay as adjuncts for years rather than move around? Status: Dormant. There are other problems with this code, as is noted in the rule. 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. The alert is related to the sonar rule : Null pointers should not be dereferenced. 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. Even if the object is null in this case, it will not give an exception and will print ' null ' to the output stream. 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. Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. Iflengthhas the value1, the addition yields 0, and png_malloc() subsequently returns a null pointer, which is assigned to chunkdata. We cannot understand how there could be a null pointer exception at the reported line. (I think you cover that in a different rule.) 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 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. Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Then we hit memcpy with length 0. Calls to extension methods are not reported because they can still operate on null values. Note that it doesn't know how to check for non-heap, non-stack. 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]. 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. This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. We really appreciate your help. Asking for help, clarification, or responding to other answers. static-code-analysis Sonar violation: Null pointers should not be dereferenced #7459 - GitHub When length is zero, it is probably unusable condition for this function. LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. By 'valid pointers' I mean that both src and dest pointers are not null and they both point to non-overlapping arrays containing at least n bytes each. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? JCP version in use: 2.6. 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. 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. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). Believing that dereferencing NULL shouldn't crash the system doesn't make it true. S2259: Null pointers should not be dereferenced - Sonar Community By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Is there a single-word adjective for "having exceptionally strong moral principles"? Is there a single-word adjective for "having exceptionally strong moral principles"? C static code analysis: Null pointers should not be dereferenced Trying to understand how to get this basic Fourier Series. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. Avoid Returning null from Methods. In C, dereferencing a null pointer is undefined behavior. res.getBody() == null || res.getBody().getServiceResult() == null). 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. Doing so will cause a NullReferenceException to be thrown. A null pointer in this position causes the read system call to fail with -EINVAL ("Invalid argument"). Null pointer - Wikipedia How do you ensure that a red herring doesn't violate Chekhov's gun? 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. @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. the Java one). 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 Pittsburgh, PA 15213-2612 Void pointers cannot be dereferenced as any other pointer. Ah, gotcha. 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). Much like dereferencing a dangling (or wild) pointer leads to undefined behavior, dereferencing a null pointer also leads to undefined behavior. Fix S2583/S2589 FP: On null check if instance is used in try block - GitHub This code also violates ERR33-C. Detect and handle standard library errors. In C++, does dereferencing a nullptr itself cause undefined behaviour One could argue that all code examples would be redundant with the first pair. VB.NET static code analysis: Null pointers should not be dereferenced IMHO, the rule title should be changed to something less general. Depending on whether the pointer is valid (i.e. Reports. EXP34-C. Do not dereference null pointers - Confluence 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. Is the God of a monotheism necessarily omnipotent? So Bar might not be initialized but then the last line of your example should not be evaluated in this case. This rule applies to all null pointers, regardless of which function returned them. At best, such an exception will cause abrupt program termination. What is generic pointer? 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. Cause we need throw our own Runtime Exception, well-known methods wont help. Unfortunately the problem is much more complex, and generally unsolvable within standard C. Consider the following example: There's no way f can check whether x points into valid memory or not. Two null pointers will always be equal to each other. Off by one error: It is the third example. To learn more, see our tips on writing great answers. Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. 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. If you call connect() function, it better do the connection, but failing simply because some ptr is NULL is not good behaviour -- failures should . This sounds indeed like a bug in the flow when an exception is raised. We resolved it by adding our tools path in the white list, and repackaging it. Java Specification Participation Agreement version in use: 2.0. How to convert the address of a dereferenced pointer from C to C# That makes sense. The result of calling such a helper function should be . 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. What is a NullPointerException, and how do I fix it? Sonar detects that res.getBody() can be null when you do the check res.getBody()==null. I've changed it to say null pointer instead of invalid pointer. Linear regulator thermal information missing in datasheet, Identify those arcade games from a 1983 Brazilian music video.