I would also guess that pointers that point to the one-past-the-end of an array are also invalid. Your assertion is not backed by the wording in the standard, nor by common implementer understanding. Does Java have support for multiline strings? It could be non-null the first time but not the second time, sonar does not know this. Then we hit memcpy with length 0. How do I align things in the following tabular environment? In C# and Java, all reference types can point to null. void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. C static code analysis: Null pointers should not be dereferenced C static code analysis Unique rules to find Bugs, Vulnerabilities, Security Hotspots, and Code Smells in your C code All rules 311 Vulnerability 13 Bug 74 Security Hotspot 18 Code Smell 206 Quick Fix 14 Tags "memset" should not be used to delete sensitive data Vulnerability Correct; a null pointer is not a valid pointer for the C library functions. sonarlint complains that Is there a proper earth ground point in this switch box? A bug can cause them never to be reassigned. You're in a company-managed project. sonarLint (3.2.) 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. 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. I'd guess WG14 has considered these questions, but I haven't until now :). 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. Depending on whether the pointer is valid (i.e. 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. The article easily misleads the reader into believeing that ensuring pointer validity boils down to checking for pointer being not equal to NULL. Even if the object is null in this case, it will not give an exception and will print ' null ' to the output stream. ability to run any cleanup processes. I feel my situation is not as complicated. To learn more, see our tips on writing great answers. Please direct comments on this JSR to the Spec Lead (s) Team. Dereferencing a null pointer results in undefined behavior. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 2008-2023 SonarSource S.A., Switzerland. 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). IDE extension that lets you fix coding issues before they exist! The final NCCE is actually more insidious than it seems at first. 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. When and how should I use a ThreadLocal variable? Thank you for clarifying your assertion until I understood it properly. EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. static-code-analysis A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures. Unlike reference types, pointer types are not tracked by the default garbage . can have the value zero on a call to that function. 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 . By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. In the meantime, Im locking this thread. 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. raiseException() return, Sonar isEmpty(Collection collection) Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. Thanks for contributing an answer to Stack Overflow! Now, you can find the list of whitelisted methods here. (I think you cover that in a different rule.) This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. A reference to null should never be dereferenced/accessed. Using platform-specific means (e.g. How can we prove that the supernatural or paranormal doesn't exist? isEmpty(Map map) attacker to bypass security measures. Instead use String.valueOf (object). Provide a self-contained reproducer (zipped project?) Explain about call by reference with an . Doing so will cause a NullReferenceException to be thrown. Thanks for the feedback. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. How can we let this pass? 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. As a result, this noncompliant code example is vulnerable to a null pointer dereference exploit, because null pointer dereferencing can be permitted on several platforms, for example, by using mmap(2) with the MAP_FIXED flag on Linux and Mac OS X, or by using the shmat() POSIX function with the SHM_RND flag [Liu 2009]. I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. And if there is no pointer_default declaration, then the default default is ref. java 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. 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). Im very new to sonar, is there a way to add methods to the whitelist? 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. Not the answer you're looking for? Passing ownership of something also requires pointers. Ticket opened : Thanks a lot for the minimalized reproducer ! This code also violates ERR33-C. Detect and handle standard library errors. . It looks like a logic bug, which can cause a memory leaking. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. With their flexibility, void pointers also bring some constraints. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. As for copy vs pointer/reference - it depends. If you preorder a special airline meal (e.g. assert(!invalid(p)); // or whatever, bool invalid(const void *p) { Things go fine now. To be precise, once length is changed to a size_t and cannot take negative values, it cannot have an invalid value. What does it mean that a reference must refer to an object, not a dereferenced null pointer? What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? But when length of A is 1, the control never reaches the else block. 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. Isn't easier just to check valid range of length? Software project. The null pointer check for writing or dereferencing should be a compiler flag or library setting. Share Improve this answer Follow answered Oct 5, 2017 at 16:27 It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); Can you please start a new thread and be more explicit about the issue you are observing. SonarLint: A "NullPointerException" could be thrown; "getBody()" can return null. https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx Solution 1, it looks like, today's solution tomorrow's problem. To learn more, see our tips on writing great answers. The correct idiom is to only allocate storage if the pointer is currently NULL. minimal code sample to reproduce (with analysis parameter, and potential instructions to compile). return p == NULL || (char *)p < &_etext; Should trycatch go inside or outside a loop? The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. Asking for help, clarification, or responding to other answers. In C/C++ speak, 'dereferencing' simply means getting the object that a pointer . It does not point to any area of memory. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. How can this new ban on drag possibly be considered constitutional? There is a missing check for the return value from . Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. Styling contours by colour and by line thickness in QGIS. How do I align things in the following tabular environment? Just a few words about the rule 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. NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. You're in a company-managed project. 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. When and how should I use a ThreadLocal variable? context.RaiseException , (/) PS: I also tried the code in android studio which uses Lint and got no warnings. But what exactly does it mean to "dereference a null pointer"? public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . Is the God of a monotheism necessarily omnipotent? Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? I suppose there is a question of "Is a pointer that points to 0 bytes valid?" Not the answer you're looking for? 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. Agreed. . I have a sonar alert on this call minRating.getRatgCaam(). But passing 0 to memcpy() is not one of them. There is no guarantee that subsequent invocations are returning the same value, thats why issue is raised. Good question! rev2023.3.3.43278. 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. I reordered that code example to do all the checks before allocations. In C, dereferencing a null pointer is undefined behavior. We cannot understand how there could be a null pointer exception at the reported line. For example the following program doesn't compile. 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). Is there a single-word adjective for "having exceptionally strong moral principles"? The result of calling such a helper function should be . 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. Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). The user_data pointer could be invalid in other ways, such as pointing to freed memory. 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. IDE extension that lets you fix coding issues before they exist! Hello. Currently I'm working with SonarQube solving issues but I'm facing a trouble to how handle null pointers that shouldn't be dereferenced. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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.. 1 Answer Sorted by: 2 Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. 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. 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 really appreciate your help. The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. It's still illegal. "After the incident", I started to be more careful not to trip over things. Carnegie Mellon University Connect and share knowledge within a single location that is structured and easy to search. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? We can see that at obj.run(), obj can not be null, but is pointed out by Sonar. How to use Slater Type Orbitals as a basis functions in matrix method correctly? I'd guess null pointers are not valid, even though they point to 0 bytes. It could be non-null the first time but not the second time, sonar does not know this. What is the point of Thrower's Bandolier? To create a custom null validation method declare an attribute with name ValidatedNotNullAttribute and mark the parameter that is Find centralized, trusted content and collaborate around the technologies you use most. It also adds assertions to document that certain other pointers must not be null. A reference to Nothing should never be dereferenced/accessed. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Find centralized, trusted content and collaborate around the technologies you use most. 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. 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. This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. 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 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. It is still a pointer though, to use it you just have to cast it to another kind of pointer first. NullPointerException is thrown when program attempts to use an object reference that has the null value. The issue arises when dereferenced pointers are used. However there is no portable way to verify that the pointer is valid, other than checking for null. Why does the second compliant example permit using possibly-null pointers? Connect and share knowledge within a single location that is structured and easy to search. 1 Answer Sorted by: 1 Your code is ok. 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, It is a false positive, but it might be a good idea not to do the, Sonar false-positive on rule: Null pointers should not be dereferenced, How Intuit democratizes AI development across teams through reusability. After that, you call res.getBody() again. Thanks for your relpy. positive S2637 in SonarQube 6.7.1 LTS, Sonar false positive, "change condition so that it does not always evaluate to true. I have checked on multiple . What does "Could not find or load main class" mean? That is why I explicitly check for this in my attempted solution. very old code or C code being worked into c++ may have functions that expect the user to delete the data. Alternate Terms Relationships Reports. 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" [4] Do "superinfinite" sets exist? There are many ways to resolve this. Minimising the environmental effects of my dyson brain. Sonar detects that res.getBody() can be null when you do the check res.getBody()==null. We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. 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. Aaron:I suspect we are talking past each other. Powered by Discourse, best viewed with JavaScript enabled. 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 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. int changed to size_t and if size_t parameter's is zero, allocate one word. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. Two null pointers will always be equal to each other. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. I added an assertion to that compliant code example. 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. I say "theoretical" because I have not successfully produced strings of this length in testing. 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. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? Powered by Discourse, best viewed with JavaScript enabled. This issues is displayed by SonarQube. Doing so will cause a NullPointerException to be thrown. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). Interactions/interfaces with C can't use references. What is null pointer exception in android. Making statements based on opinion; back them up with references or personal experience. 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. name result . I added a comment to explain that SIZE_MAX is the limit of size_t. Can I tell police to wait and call a lawyer when served with a search warrant? SonarQube Version 6.7.2 (build 37468) 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. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. 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. 3.Null pointers should not be derefer enced/accessed. How to tell which packages are held back due to phased updates. Connect and share knowledge within a single location that is structured and easy to search. What sort of strategies would a medieval military use against a fantasy giant? 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. What are the effects of exceptions on performance in Java? 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]. I believe in this case, either expression would work. And the semantics, as I said, are different. An awesome tip to avoid NPE is to return empty strings or empty collections rather than null. Some Interesting Facts: 1) void pointers cannot be dereferenced. That makes sense. I suggest that this topic needs to include calloc() and realloc() Refer to Linux man pages online for more enlightenment about malloc(), and friends. A pointer to null (the 0 memory address) should never be dereferenced/accessed.
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