I added an assertion to that compliant code example. 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. 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. 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. However there is no portable way to verify that the pointer is valid, other than checking for null. Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. IDE extension that lets you fix coding issues before they exist! 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). . Maybe one of these methods is already doing what your methods is doing, and could be considered as replacement. 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. To learn more, see our tips on writing great answers. "After the incident", I started to be more careful not to trip over things. Software Engineering Institute Good question! sonar-java. At worst, it could expose debugging information that would be useful to an attacker, or I'd guess WG14 has considered these questions, but I haven't until now :). 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. So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). int changed to size_t and if size_t parameter's is zero, allocate one word. If malloc() fails, it returns a null pointer that is assigned to c_str. This solution also ensures that theuser_data pointer is not 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. PS: I also tried the code in android studio which uses Lint and got no warnings. Thus we should check > this kstrdup() operation. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); This likely means that youre on an ancient version of the Java analyzer. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. 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. 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" I feel my situation is not as complicated. Thanks for contributing an answer to Stack Overflow! Is there a single-word adjective for "having exceptionally strong moral principles"? But when length of A is 1, the control never reaches the else block. 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). In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. SonarJava. 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. Why does Mister Mxyzptlk need to have a weakness in the comics? 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. Does a summoned creature play immediately after being summoned by a ready action? Im very new to sonar, is there a way to add methods to the whitelist? validated for null in your method declaration with it: 2008-2023 SonarSource S.A., Switzerland. That is, sets equivalent to a proper subset via an all-structure-preserving bijection. This sounds indeed like a bug in the flow when an exception is raised. The correct idiom is to only allocate storage if the pointer is currently NULL. Possible fix: Assign a valid address to the pointer in all branches of the conditional statement.. Pointer can point to dynamically allocated memory. Find centralized, trusted content and collaborate around the technologies you use most. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. I say "theoretical" because I have not successfully produced strings of this length in testing. 3.7. , RemoteContext new ExceptionType() RemoteContext , SonarLintJava (), java - sonarLint "Null pointers should not be dereferenced (squid:S2259)"Stack Overflow return p == NULL || (char *)p < &_etext; A pointer is simply a variable that contains a memory address. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. Is there a single-word adjective for "having exceptionally strong moral principles"? 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. Even if the object is null in this case, it will not give an exception and will print ' null ' to the output stream. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. How do I align things in the following tabular environment? 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. Not the answer you're looking for? Are there tables of wastage rates for different fruit and veg? When B is null, The control reaches inside the main if block only when length of A is 1. 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. Reports. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. 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. 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. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . Issues Components. This compliant solution ensures that the pointer returned by png_malloc() is not null. But what exactly does it mean to "dereference a null pointer"? Accessing or modifying a null object's field. Connect and share knowledge within a single location that is structured and easy to search. Making statements based on opinion; back them up with references or personal experience. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. My question is; is my solution incorrect? Just a few words about the rule now. 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. It could be non-null the first time but not the second time, sonar does not know this. 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. This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. Dereferencing a null pointer is undefined behavior. 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. Is the God of a monotheism necessarily omnipotent? How do you ensure that a red herring doesn't violate Chekhov's gun? How do I align things in the following tabular environment? LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. 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 . In my experience, there are reasons to check for a NULL pointer other than dereferencing it. Is a PhD visitor considered as a visiting scholar? A bug can cause them never to be reassigned. Can I tell police to wait and call a lawyer when served with a search warrant? Issues Components. 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. That is why I explicitly check for this in my attempted solution. How handle the initialization of "responseDto" without "null" because is throwing the issue on sonar. Can I tell police to wait and call a lawyer when served with a search warrant? Calls to extension methods are not reported because they can still operate on null values. Put a new ResponseEntity is wrong because I won't know what will be the answer for the status of http. Share Improve this answer Follow answered Oct 5, 2017 at 16:27 To subscribe to this RSS feed, copy and paste this URL into your RSS reader. NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. 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.