null pointers should not be dereferenced

I've changed it to say null pointer instead of invalid pointer. static-code-analysis extern char _etext; 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. 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. Provide a self-contained reproducer (zipped project?) If copying takes place between objects that overlap, the behavior is undefined. Doing so will at best cause abrupt program termination, without the Seems the analizer don't recognice the logic with the funcional object Optional. 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. This likely means that youre on an ancient version of the Java analyzer. io.NotSerializableException : java. Trying to understand how to get this basic Fourier Series. [4] By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Dereferencing a null pointer results in undefined behavior. The issue arises when dereferenced pointers are used. 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. We have a false positive with the " Null pointers should not be dereferenced -squid:S2259" rule : We have a "NullPointerException" false positive for which we do not know how to solve it. Status: Dormant. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. @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. Is there a single-word adjective for "having exceptionally strong moral principles"? Solution 1, it looks like, today's solution tomorrow's problem. How can we prove that the supernatural or paranormal doesn't exist? 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. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. Accessing or modifying a null object's field. 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. And fwstr > is dereferenced in the following codes. 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. How do you ensure that a red herring doesn't violate Chekhov's gun? 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. Some Interesting Facts: 1) void pointers cannot be dereferenced. What are the effects of exceptions on performance in Java? When a variable is declared as being a pointer to type void, it is known as a generic pointer. That is only true if possibleNumbers contains no element.. BTW: none of these warnings are shown by . Find centralized, trusted content and collaborate around the technologies you use most. How do I align things in the following tabular environment? What sort of strategies would a medieval military use against a fantasy giant? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Asking for help, clarification, or responding to other answers. Im very new to sonar, is there a way to add methods to the whitelist? Haiku is a free and open-source operating system for PC designed to be binary compatible with the BeOS operating system and embodying the basic ideas of BeOS. Minimising the environmental effects of my dyson brain. This cross-file approach analysis can be quite resource-consuming, and we are not ready to openly enable the feature. assert(!invalid(p)); // or whatever, bool invalid(const void *p) { Im having trouble understanding your problem. // <------- 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. Making statements based on opinion; back them up with references or personal experience. 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. The final NCCE is actually more insidious than it seems at first. Linear regulator thermal information missing in datasheet, Identify those arcade games from a 1983 Brazilian music video. SonarQube - Null Pointer Dereference Issue java simonsirak (Simon Sirak) June 14, 2018, 1:18pm 1 Hi! At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . IMHO, the rule title should be changed to something less general. Are there tables of wastage rates for different fruit and veg? To learn more, see our tips on writing great answers. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? 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). I reordered that code example to do all the checks before allocations. Write a semantic patch to nd cases where the result of calling kmalloc is dereferenced with no previous NULL pointer test. As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. can have the value zero on a call to that function. Issues Components. When B is null, The control reaches inside the main if block only when length of A is 1. 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. res.getBody() == null || res.getBody().getServiceResult() == null). All rights are expressly reserved. Software Engineering Institute 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. Sonar is ok. Why are physically impossible and logically impossible concepts considered separate in terms of probability? that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Believing that dereferencing NULL shouldn't crash the system doesn't make it true. 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. Java Specification Participation Agreement version in use: 2.0. Ticket opened : Thanks a lot for the minimalized reproducer ! Batch split images vertically in half, sequentially numbering the output files, Recovering from a blunder I made while emailing a professor. 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. A reference to Nothing should never be dereferenced/accessed. To learn more, see our tips on writing great answers. Appropriate typecasting is necessary. Thanks for contributing an answer to Stack Overflow! Pittsburgh, PA 15213-2612 Dereferencing a null pointer is undefined behavior, typically abnormal program termination. I'd guess WG14 has considered these questions, but I haven't until now :). There are many ways to resolve this. 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. Null pointer should not be dereferenced , 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. 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. return p == NULL || (char *)p < &_etext; This will normally lead to an unhandled error, resulting in a segmentation fault. )}"); In C, dereferencing a null pointer is undefined behavior. 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. rev2023.3.3.43278. best, such an exception will cause abrupt program termination. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. Off by one error: It is the third example. 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 . What does it mean that a reference must refer to an object, not a dereferenced null pointer? The correct idiom is to only allocate storage if the pointer is currently NULL. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. 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. 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. The 4gig boundary will probably be important too with unsigned int in LP64, but since size_t will be 64-bit, there will have to be some truncation that compilers will be able to warn on. When exploring such methods, the engine then deduces behaviors regarding null-checking (among other things). Which @NotNull Java annotation should I use? in above code, These can be: Invoking a method from a null object. At Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. I feel my situation is not as complicated. What is generic pointer? Powered by Discourse, best viewed with JavaScript enabled. I would also guess that pointers that point to the one-past-the-end of an array are also invalid. 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. Find centralized, trusted content and collaborate around the technologies you use most. Is null check needed before calling instanceof? What is null pointer exception in android. ability to run any cleanup processes. Sonar is ok. Sonar can't determine that the helper method did the null validation. Find centralized, trusted content and collaborate around the technologies you use most. 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 common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. A reference to null should never be dereferenced/accessed. Cause we need throw our own Runtime Exception, well-known methods wont help. Find centralized, trusted content and collaborate around the technologies you use most. I suppose there is a question of "Is a pointer that points to 0 bytes valid?" By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. PS: I also tried the code in android studio which uses Lint and got no warnings. And if there is no pointer_default declaration, then the default default is ref. 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. (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). Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Null pointers should not be dereferenced. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. which version of SonarQube are you using? How do you ensure that a red herring doesn't violate Chekhov's gun? Mutually exclusive execution using std::atomic? Using Kolmogorov complexity to measure difficulty of problems? Asking for help, clarification, or responding to other answers. Hi @Michael! 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. Is there a proper earth ground point in this switch box? In C/C++ speak, 'dereferencing' simply means getting the object that a pointer . Is there a proper earth ground point in this switch box? ncdu: What's going on with this second size column? Report False-positive / False-negative [LTS] The new SonarQube LTS is here: SONARQUBE 9.9 LTS, SonarQube - Null Pointer Dereference Issue. ", Eclipse - Sonar S2629 possible false positive with new String, SonarQube null pointers should not be dereferenced on try/catch, getTextContent() through "Null pointers should not be dereferenced". It is still a pointer though, to use it you just have to cast it to another kind of pointer first. I believe in this case, either expression would work. When you have a variable of non-primitive type, it is a reference to an object. Thanks for contributing an answer to Stack Overflow! Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. context.RaiseException , (/) 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. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Should trycatch go inside or outside a loop? Identify where the allocation occurs. (C11, S7.24.2.1). Thanks, David! At worst, it could expose debugging information that would be useful to an attacker or it could allow an sonar-java. 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). NullPointerException is thrown when program attempts to use an object reference that has the null value. java That interpretation of the standard is not supported universally. Passing ownership of something also requires pointers. ii. ), Does not guess that return values from malloc(), strchr(), etc., can be NULL (The return value from malloc() is NULL only if there is OOMo and the dev might not care to handle that. 1 Null pointers should not be dereferenced @CheckForNull String getName(){.} I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). In order to fix this, just do the following: If you are absolutely sure that res.getBody() stays null and is also not modified by another thread, you could also use a //NOSONAR comment in order to suppress the warning. 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. The same problem we will have with "Add at least one assertion to this test case." sonarlint, sonarLint (3.2.) SonarLint: A "NullPointerException" could be thrown; "getBody()" can return null. Using platform-specific means (e.g. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. I don't need to do this validation again. As for copy vs pointer/reference - it depends. Can you please start a new thread and be more explicit about the issue you are observing. Please explain: Without this, we wont be able to help you. 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. Check whether a String is not Null and not Empty. rev2023.3.3.43278. 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. 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. > Further, if kstrdup() returns NULL, we should return ERR_PTR(-ENOMEM) to > the caller site. NULL vs Uninitialized pointer - An uninitialized pointer stores an undefined value. The only potential null is the return value of list(). The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. Explain about call by reference with an . . Obviously the value of that pointer could have changed since the . However there is no portable way to verify that the pointer is valid, other than checking for null. Recovering from a blunder I made while emailing a professor. Connect and share knowledge within a single location that is structured and easy to search. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. vegan) just to try it, does this inconvenience the caterers and staff? Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. 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. Optimizers are optimizing based on this latitude and have been for years. }. EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. 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. This sounds indeed like a bug in the flow when an exception is raised. . JCP version in use: 2.6. I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. The null pointer check for writing or dereferencing should be a compiler flag or library setting. - the incident has nothing to do with me; can I use this this way? The test was added to catch the possibly theoretical situation where the length of input_str was somehow the maximum size for size_t, and adding one to this size in the malloc expression (to allocated space for the trailing null byte) results in an integer overflow. context.RaiseException . 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 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. 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. 3.Null pointers should not be derefer enced/accessed. 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 adds assertions to document that certain other pointers must not be null. 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. Carnegie Mellon University On many platforms, dereferencing a null pointer results in abnormal program termination, but this is not required by the standard. We. The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. Making statements based on opinion; back them up with references or personal experience. Trying to understand how to get this basic Fourier Series. IDE extension that lets you fix coding issues before they exist! So, this code should address the Sonar problem: You can also eliminate the null check using Optional>, like: Even I don't recommend this, you can just check the null responseDto without any use of Optional: Thanks for contributing an answer to Stack Overflow! All rights are expressly reserved. At best, such an exception will cause abrupt program termination. Software project. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. Sonar detects that res.getBody() can be null when you do the check res.getBody()==null. versions used (SonarQube, Scanner, language analyzer) In the meantime, Im locking this thread. The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. - the incident has nothing to do with me; can I use this this way? At this point we define size as strlen(input_str) + 1. Unlike reference types, pointer types are not tracked by the default garbage . NullPointerException is a RuntimeException. This issues is displayed by SonarQube. 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. 11 Sep, 2006. A reference to null should never be dereferenced/accessed. Whoops, you're right. minimal code sample to reproduce (with analysis parameter, and potential instructions to compile). 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"). But no where in that particular idiom would a NULL pointer necessarily be deferenced. . 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(). which would allow us to systematically observe what you are having. Revert Update S2259: "Null pointer dereference" CFG should ignore expressions in Debug.Assert #397 Introduce means to not raise "Expression always true/false" on values that were checked with Debug.Assert.