Dereferencing a null pointer is undefined behavior. You need to benchmark. Can I tell police to wait and call a lawyer when served with a search warrant? ), 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). What does it mean that a reference must refer to an object, not a dereferenced null pointer? This latter use of pointers is a combined boolean/satellite: the pointer being non-null indicates "I have this sister object", and it provides that object. raiseException() return, Sonar You can compare a pointer with NULL to test for the special condition. Does Counterspell prevent from any further spells being cast on a given turn? Identify where the allocation occurs. 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. Thus we should check > this kstrdup() operation. [4] My main problem is because I'm doing a restTemplate.exchange with try-catch and declaring a variable with null value before the clause try and then using it inside the try. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. At best, such an exception will cause abrupt program termination. Making statements based on opinion; back them up with references or personal experience. Why are physically impossible and logically impossible concepts considered separate in terms of probability? I reordered that code example to do all the checks before allocations. 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. Dereferencing a null pointer is undefined behavior, typically abnormal program termination. Does a summoned creature play immediately after being summoned by a ready action? rev2023.3.3.43278. 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. We can see that at obj.run(), obj can not be null, but is pointed out by Sonar. Why does the second compliant example permit using possibly-null pointers? How do you ensure that a red herring doesn't violate Chekhov's gun? Unfortunately, its actual state also has some limitations, like the one you are hitting here. It also adds assertions to document that certain other pointers must not be null. Solution 1, it looks like, today's solution tomorrow's problem. Extended Description NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. (I think you cover that in a different rule.) Im having trouble understanding your problem. - the incident has nothing to do with me; can I use this this way? uninitialized reference-type class members. Is there a single-word adjective for "having exceptionally strong moral principles"? sonarLint (3.2.) Thanks for your relpy. 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. Connect and share knowledge within a single location that is structured and easy to search. 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. Why do academics stay as adjuncts for years rather than move around? When length is zero, it is probably unusable condition for this function. 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. 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. 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 return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. How handle the initialization of "responseDto" without "null" because is throwing the issue on sonar. Issues Components. I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. The standard will simply copy 0 byteswhich is essentially a no-op. 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.) Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Sonar false-positive on rule: Null pointers should not be dereferenced, Null Pointer Dereference issue not detected when the pointer is returned by another function. It is still a pointer though, to use it you just have to cast it to another kind of pointer first. sometimes FP occurs. Using platform-specific means (e.g. Off by one error: It is the third example. 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. 2008-2023 SonarSource S.A., Switzerland. What is pointed to should only be deleted if it was created with new. That is why I explicitly check for this in my attempted solution. When B is null, The control reaches inside the main if block only when length of A is 1. As for copy vs pointer/reference - it depends. To learn more, see our tips on writing great answers. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? In this case, the difference is the assumption thatmalloc() always returns non-nullfor the second NCCE, whereas the first NCCE has themalloc() abstracted away. Do not dereference null pointers Created by Jeffrey Gennari, last modified by Jill Britton on Jan 18, 2023 Dereferencing a null pointer is undefined behavior. ability to run any cleanup processes. 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. ROSE does not handle cases where an allocation is assigned to an lvalue that is not a variable (such as a struct member or C++ function call returning a reference), Finds instances where a pointer is checked against NULL and then later dereferenced, Identifies functions that can return a null pointer but are not checked, Identifies code that dereferences a pointer and then checks the pointer against NULL, Can find the instances where NULL is explicitly dereferenced or a pointer is checked againstNULL but then dereferenced anyway. Now (sonarqube java analyzer version 4.3.0.7717) it's supported and works fine. This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. And the semantics, as I said, are different. Software project. return p == NULL || (char *)p < &_etext; res.getBody() == null || res.getBody().getServiceResult() == null). Doing so will cause a NullPointerException to be thrown. In C, dereferencing a null pointer is undefined behavior. Batch split images vertically in half, sequentially numbering the output files, Difficulties with estimation of epsilon-delta limit proof, Minimising the environmental effects of my dyson brain. Trying to understand how to get this basic Fourier Series. At best, such an exception will cause abrupt program termination. Finally my method is returning a response with value of restTemplate. Automated Detection Null pointer dereferences can happen in path-dependent ways. When and how should I use a ThreadLocal variable? Instead use String.valueOf (object). This issues is displayed by SonarQube. Can you please start a new thread and be more explicit about the issue you are observing. Issues Components. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); Currently I'm working with SonarQube solving issues but I'm facing a trouble to how handle null pointers that shouldn't be dereferenced. context.RaiseException . There are other problems with this code, as is noted in the rule. I have a sonar alert on this call minRating.getRatgCaam(). . Carnegie Mellon University Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Styling contours by colour and by line thickness in QGIS. Doing so will at best cause abrupt program termination, without the At Such long getter chains can also be replaced with Optional + map + ifPresent lambda style. 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. I am a student implementing stack with singly linked list using C, following a book called Fundamentals of Data Structures in C.. I've changed it to say null pointer instead of invalid pointer. There is no guarantee that subsequent invocations are returning the same value, thats why issue is raised. Now, you can find the list of whitelisted methods here. validated for null in your method declaration with it: 2008-2023 SonarSource S.A., Switzerland. In C# and Java, all reference types can point to null. Dereferencing > this null pointer may cause the kernel go wrong. We cannot understand how there could be a null pointer exception at the reported line. 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. A null pointer in this position causes the read system call to fail with -EINVAL ("Invalid argument"). Put a new ResponseEntity is wrong because I won't know what will be the answer for the status of http. All rights are expressly reserved. SonarQube - Null Pointer Dereference Issue java simonsirak (Simon Sirak) June 14, 2018, 1:18pm 1 Hi! 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. 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. 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 . https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx Find centralized, trusted content and collaborate around the technologies you use most. util.regex.Matcher, java - Swing .getParent() . Making statements based on opinion; back them up with references or personal experience. 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). 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. Is there a proper earth ground point in this switch box? Thanks for contributing an answer to Stack Overflow! Coverity Prevent cannot discover all violations of this rule, so further verification is necessary, Detects when NULL is dereferenced (Array of pointers is not checked. // <------- 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. But even with this, the concerned object it tagged as a possible NullPointerException problem. that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. Shouldn't the function check all pointers before dereferencing them or passing them to another function? 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. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. 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). 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(). The same problem we will have with "Add at least one assertion to this test case." (from res.getBody().getServiceResult() ). Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. Cause we need throw our own Runtime Exception, well-known methods wont help. (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). 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). Not the answer you're looking for? The only potential null is the return value of list(). The expected result here is solve the issue with sonarqube. Not the answer you're looking for? Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. I suppose there is a question of "Is a pointer that points to 0 bytes valid?" A reference to null should never be dereferenced/accessed. Isn't easier just to check valid range of length? 0 is certainly within the 'domain of the function' (a phrase defined by mathematics but not by C11), as copying 0 bytes is well-understood (although silly). A bug can cause them never to be reassigned. Then the reading of the buffer via bstr_printf() will then look at the pointer to process the final output. rev2023.3.3.43278. IMHO, the rule title should be changed to something less general. Is it possible to create a concave light? extern char _etext; Recovering from a blunder I made while emailing a professor. So the SIZE_MAX check was unnecessary. 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. Making statements based on opinion; back them up with references or personal experience. Iflengthhas the value1, the addition yields 0, and png_malloc() subsequently returns a null pointer, which is assigned to chunkdata. rev2023.3.3.43278. Is there a proper earth ground point in this switch box? This is a matter of style, and also following code walkthrough. 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. My question is; is my solution incorrect? However there is no portable way to verify that the pointer is valid, other than checking for null. SonarQube Version 6.7.2 (build 37468) 3.Null pointers should not be derefer enced/accessed. Explain about call by reference with an . Unlike reference types, pointer types are not tracked by the default garbage . 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. 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 We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. Since you cannot have a variable of type void, the pointer will not point to any data and therefore cannot be dereferenced. The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. Please explain: Without this, we wont be able to help you. Agreed. 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. 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 . Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. it could allow an attacker to bypass security measures. Im currently using SonarQube version 5.6.6. better way to handle this is to store the result of method invocation in a variable. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Obviously the value of that pointer could have changed since the . Good question! ncdu: What's going on with this second size column? But when length of A is 1, the control never reaches the else block. 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. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? Ah, gotcha. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . . Key here (explains table format and definitions), EXP34-C = Union( CWE-690, list) where list =. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) Hi Andreas, Thanks for the feedback. Is it possible to rotate a window 90 degrees if it has the same length and width? A NULL pointer can be dereferenced when signatures are being verified on PKCS7 signed or signedAndEnveloped data. 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, how to handle Sonarlint java:S2259 (Null pointers should not be dereferenced), How Intuit democratizes AI development across teams through reusability. Mutually exclusive execution using std::atomic? attacker to bypass security measures. Interactions/interfaces with C can't use references. ncdu: What's going on with this second size column? In the meantime, Im locking this thread. 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.

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