null pointers should not be dereferenced
Trying to understand how to get this basic Fourier Series. I added a comment to explain that SIZE_MAX is the limit of size_t. To learn more, see our tips on writing great answers. which would allow us to systematically observe what you are having. We cannot understand how there could be a null pointer exception at the reported line. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. 3.7. Just because something is a pointer does not mean you should call delete . As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. My below code where I'm calling a stored procedure is giving a null pointer exception. This code also violates ERR33-C. Detect and handle standard library errors. "After the incident", I started to be more careful not to trip over things. 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. A pointer is simply a variable that contains a memory address. That's true. 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. I believe in this case, either expression would work. 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. To create a custom null validation method declare an attribute with name ValidatedNotNullAttribute and mark the parameter that is As for copy vs pointer/reference - it depends. Seems the analizer don't recognice the logic with the funcional object Optional. 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). This noncompliant code example is derived from a real-world example taken from a vulnerable version of the libpng library as deployed on a popular ARM-based cell phone [Jack 2007]. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. 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. What is generic pointer? Doing so will cause a NullReferenceException to be thrown. positive S2637 in SonarQube 6.7.1 LTS, SonarQube for MSBuild not reporting quality issues, getTextContent() through "Null pointers should not be dereferenced". The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures. 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. The value 0 for the number of bytes to copy is not what causes the UB, it's the null pointer value which triggers it. And if there is no pointer_default declaration, then the default default is ref. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? 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. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. If not, this might be a bug. To learn more, see our tips on writing great answers. Dereferencing a null pointer results in undefined behavior. Put a new ResponseEntity is wrong because I won't know what will be the answer for the status of http. I would also guess that pointers that point to the one-past-the-end of an array are also invalid. Many platforms can support testing for those also. In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. 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. ii. [4] If you call connect() function, it better do the connection, but failing simply because some ptr is NULL is not good behaviour -- failures should . I reordered that code example to do all the checks before allocations. What is the point of Thrower's Bandolier? I feel my situation is not as complicated. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). The expected result here is solve the issue with sonarqube. Passing ownership of something also requires pointers. Solution 1, it looks like, today's solution tomorrow's problem. extern char _etext; Sonar detects that res.getBody() can be null when you do the check res.getBody()==null. Does Counterspell prevent from any further spells being cast on a given turn? Is null check needed before calling instanceof? You're in a company-managed project. Whats the grammar of "For those whose stories they are"? Instead use String.valueOf (object). Java Specification Participation Agreement version in use: 2.0. If the project is not compiled, and without sonar.java.binaries whether the white list takes effect? That is, sets equivalent to a proper subset via an all-structure-preserving bijection. 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 think you cover that in a different rule.) If you say [in] or [out] without a modifier, then the modifier defaults to the pointer_default for the enclosing class. A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. sonarlint complains that Could I capture, and I would be able to glean much security information from the dump? It could be non-null the first time but not the second time, sonar does not know this. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Please explain: Without this, we wont be able to help you. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. Are there tables of wastage rates for different fruit and veg? But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. Software project. SonarQube Version 6.7.2 (build 37468) How can we prove that the supernatural or paranormal doesn't exist? return p == NULL || (char *)p < &_etext; Do "superinfinite" sets exist? Then we hit memcpy with length 0. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. What methods/tools can be used to determine the cause so that you stop the exception from causing the progra. Trying to understand how to get this basic Fourier Series. In the simplest case, this function just returns the result of calling kmalloc. Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. Does Java have support for multiline strings? We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. 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. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. That makes sense. Isn't easier just to check valid range of length? 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(). Is the God of a monotheism necessarily omnipotent? I have checked on multiple . 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 This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. After that, you call res.getBody() again. Provide a self-contained reproducer (zipped project?) To subscribe to this RSS feed, copy and paste this URL into your RSS reader. ability to run any cleanup processes. Making statements based on opinion; back them up with references or personal experience. A value is checked here to see whether it is null, but this value can't be null because it was previously dereferenced and if it were null a null pointer exception would have occurred at the earlier dereference. isEmpty(Collection collection) The only potential null is the return value of list(). public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . It also adds assertions to document that certain other pointers must not be null. Doing so will cause a NullPointerException to be thrown. validated for null in your method declaration with it: 2008-2023 SonarSource S.A., Switzerland. Appropriate typecasting is necessary. 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. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Hi @Michael! I suppose there is a question of "Is a pointer that points to 0 bytes valid?" 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). So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. The Clang Static Analyzer already has a checker to find the null pointer dereference in code, however it is not sufficient for higher abstractions such as C++ smart pointers or optionals. 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. very old code or C code being worked into c++ may have functions that expect the user to delete the data. SonarQube null pointers should not be dereferenced on try/catch, Sonarcube :Null pointers should not be dereferenced, How do you get out of a corner when plotting yourself into a corner. context.RaiseException . Ah, gotcha. positive S2637 in SonarQube 6.7.1 LTS, Sonar false positive, "change condition so that it does not always evaluate to true. Depending on whether the pointer is valid (i.e. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Trying to understand how to get this basic Fourier Series. Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. A pointer to null (the 0 memory address) should never be dereferenced/accessed. Small typo nit: "such as if i t pointed to freed memory" meant to say "if it" instead (removing whitespace). Find centralized, trusted content and collaborate around the technologies you use most. 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 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. Key here (explains table format and definitions), EXP34-C = Union( CWE-690, list) where list =. Why is there a voltage on my HDMI and coaxial cables? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. CWE-476: NULL Pointer Dereference: 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. This is a matter of style, and also following code walkthrough. 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. That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. . Trying to understand how to get this basic Fourier Series. This code also violates ERR33-C. Detect and handle standard library errors. Alternate Terms Relationships - the incident has nothing to do with me; can I use this this way? EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. Not the answer you're looking for? 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). How do I align things in the following tabular environment? This cross-file approach analysis can be quite resource-consuming, and we are not ready to openly enable the feature. The same problem we will have with "Add at least one assertion to this test case." See the "Null pointer checks may be optimized away more aggressively" section inhttps://gcc.gnu.org/gcc-4.9/porting_to.htmlas an example with one common implementation. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. A NULL pointer can be dereferenced when signatures are being verified on PKCS7 signed or signedAndEnveloped data. Making statements based on opinion; back them up with references or personal experience. What does it mean that a reference must refer to an object, not a dereferenced null pointer? Extended Description NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. 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. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? best, such an exception will cause abrupt program termination. Such long getter chains can also be replaced with Optional + map + ifPresent lambda style. Recovering from a blunder I made while emailing a professor. It's a modular system with the . By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. it could allow an attacker to bypass security measures. Goal int changed to size_t and if size_t parameter's is zero, allocate one word. Share Improve this answer Follow answered Oct 5, 2017 at 16:27 And the semantics, as I said, are different. Ticket opened : Thanks a lot for the minimalized reproducer ! SIZE_MAX is the largest possible value that a size_t could take, so it is not possible to have anything larger than SIZE_MAX. I'd guess WG14 has considered these questions, but I haven't until now :). How do you ensure that a red herring doesn't violate Chekhov's gun? You can use Optional instead. 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. Two null pointers will always be equal to each other. And fwstr > is dereferenced in the following codes. 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. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); So, this code should address the Sonar problem: You can also eliminate the null check using Optional
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