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. On many platforms, dereferencing a null pointer results inabnormal program termination, but this is not required by the standard. Dereferencing a null pointer is undefined behavior, typically abnormal program termination. 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). Could I capture, and I would be able to glean much security information from the dump? SonarQube - Null Pointer Dereference Issue java simonsirak (Simon Sirak) June 14, 2018, 1:18pm 1 Hi! However there is no portable way to verify that the pointer is valid, other than checking for null. That is only true if possibleNumbers contains no element.. BTW: none of these warnings are shown by . And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). How do I align things in the following tabular environment? 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. ncdu: What's going on with this second size column? Is a PhD visitor considered as a visiting scholar? This compliant solution ensures that the pointer returned by png_malloc() is not null. Dereferencing a null pointer is undefined behavior. the Java one). What methods/tools can be used to determine the cause so that you stop the exception from causing the progra. C# static code analysis: Null pointers should not be dereferenced Products In-IDE IDE extension that lets you fix coding issues before they exist! I reordered that code example to do all the checks before allocations. However, memory allocation > functions such as kstrdup() may fail and returns NULL. The result of calling such a helper function should be . All rights are expressly reserved. What is generic pointer? 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. I'd guess WG14 has considered these questions, but I haven't until now :). 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. 1 Answer Sorted by: 1 Your code is ok. How do you ensure that a red herring doesn't violate Chekhov's gun? rev2023.3.3.43278. Find centralized, trusted content and collaborate around the technologies you use most. 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 . By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. In C# and Java, all reference types can point to null. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Trying to understand how to get this basic Fourier Series. Void pointers cannot be dereferenced as any other pointer. Is it possible to create a concave light? Java Specification Participation Agreement version in use: 2.0. 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. A pointer to null (the 0 memory address) should never be dereferenced/accessed. This code also violates ERR33-C. Detect and handle standard library errors. 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. Mutually exclusive execution using std::atomic? IMHO, the rule title should be changed to something less general. IDE extension that lets you fix coding issues before they exist! Batch split images vertically in half, sequentially numbering the output files, Recovering from a blunder I made while emailing a professor. Calls to extension methods are not reported because they can still operate on null values. Believing that dereferencing NULL shouldn't crash the system doesn't make it true. A reference to null should never be dereferenced/accessed. rev2023.3.3.43278. SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. Styling contours by colour and by line thickness in QGIS. If you call connect() function, it better do the connection, but failing simply because some ptr is NULL is not good behaviour -- failures should . But when length of A is 1, the control never reaches the else block. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx Null pointer should not be dereferenced . very old code or C code being worked into c++ may have functions that expect the user to delete the data. 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" By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Some Interesting Facts: 1) void pointers cannot be dereferenced. SonarQube Version 6.7.2 (build 37468) Making statements based on opinion; back them up with references or personal experience. Is the God of a monotheism necessarily omnipotent? This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? Provide a self-contained reproducer (zipped project?) Minimising the environmental effects of my dyson brain. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. Why does the second compliant example permit using possibly-null pointers? The method isNR(minRating) is a helper method that validate among other things, if the object minRating is null. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . As for copy vs pointer/reference - it depends. 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. 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. Iflengthhas the value1, the addition yields 0, and png_malloc() subsequently returns a null pointer, which is assigned to chunkdata. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. There is no guarantee that subsequent invocations are returning the same value, thats why issue is raised. vegan) just to try it, does this inconvenience the caterers and staff? 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. 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.. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. But what exactly does it mean to "dereference a null pointer"? Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. When and how should I use a ThreadLocal variable? rev2023.3.3.43278. It could be non-null the first time but not the second time, sonar does not know this. When length is zero, it is probably unusable condition for this function. 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. Connect and share knowledge within a single location that is structured and easy to search. NULL vs Uninitialized pointer - An uninitialized pointer stores an undefined value. 11 Sep, 2006. NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. I added a comment to explain that SIZE_MAX is the limit of size_t. Such long getter chains can also be replaced with Optional + map + ifPresent lambda style. When B is null, The control reaches inside the main if block only when length of A is 1. Making statements based on opinion; back them up with references or personal experience. That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. sonar-java. {"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. 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. 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. A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. https://stackoverflow.com/questions/47534436/, https://stackoverflow.com/questions/47534436/, java - Jenkins groovy : Error: java. This code also violates ERR33-C. Detect and handle standard library errors. http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html. At best, such an exception will cause abrupt program termination. Small typo nit: "such as if i t pointed to freed memory" meant to say "if it" instead (removing whitespace). In Java, a special null value can be assigned to an object reference. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Appropriate typecasting is necessary. 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. Making statements based on opinion; back them up with references or personal experience. io.NotSerializableException : java. 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 */ return p == NULL || (char *)p < &_etext; A reference to Nothing should never be dereferenced/accessed. This sounds indeed like a bug in the flow when an exception is raised. it could allow an attacker to bypass security measures. Issues Components. It looks like a logic bug, which can cause a memory leaking. I'd guess null pointers are not valid, even though they point to 0 bytes. It also adds assertions to document that certain other pointers must not be null. Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. For the time being, I would unfortunately recommend to mark as False Positive the issue. 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. We resolved it by adding our tools path in the white list, and repackaging it. 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. Does Java have support for multiline strings? Just a few words about the rule now. A bug can cause them never to be reassigned. ), 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). 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. Is there a proper earth ground point in this switch box? 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 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. If you try to access any member variables or methods with that variable, you are trying to dereference it. To learn more, see our tips on writing great answers. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. How handle the initialization of "responseDto" without "null" because is throwing the issue on sonar. ncdu: What's going on with this second size column? Not the answer you're looking for? Can I tell police to wait and call a lawyer when served with a search warrant? 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. That makes sense. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. It does not point to any area of memory. I guess you could write a proposal to modify the C Standard, but our coding standard is meant to provide guidance for the existing language. Aaron:I suspect we are talking past each other. Thank you for clarifying your assertion until I understood it properly. 1 Null pointers should not be dereferenced @CheckForNull String getName(){.} As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. util.regex.Matcher, java - Swing .getParent() . I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). Basically, yes. Off by one error: It is the third example. Recovering from a blunder I made while emailing a professor. In case the hash algorithm used for the signature is known to the OpenSSL library but the implementation of the hash algorithm is not available the digest initialization will fail. In C, dereferencing a null pointer is undefined behavior. But when length of A is 1, the control never reaches the else block. Linear regulator thermal information missing in datasheet, Identify those arcade games from a 1983 Brazilian music video. This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. , NPE : null-, . Good question! . 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.