Consider the following example of a typical client server exchange. This code also violates ERR33-C. Detect and handle standard library errors. The description The sk pointer is initialized to tun->sk before checking if tun is a null pointer. is provided for a non-compliant code example.Thus it seems that the arrow operator (member access through pointer) is usually treated also as a dereference operation. Fixed by setting name to Oh joy. 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. One situation this can happen is when the pointer has been checked against NULL and is dereferenced later. Find centralized, trusted content and collaborate around the technologies you use most. Variant - a weakness NULL Pointer Dereference in mrb_vm_exec with super in GitHub. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). If you don't set it again before the above if statement, that means that the NULL check is unnecessary and should be removed. It should be an ingrained practice. Why refined oil is cheaper than cold press oil? Example: educators, technical writers, and project/program managers. This defect on our template caused null pointer deferencing in over hundred use cases. What is this brick with a round back and a stud on the side used for? It modifies the pointed-to data. Ah, gotcha. These types of problems usually lead to insidious correctness errors since exceptions are caught at a higher level. CWE, CWSS, CWRAF, and the CWE logo are trademarks of The MITRE Corporation. EXP34-C. Do not dereference null pointers - Confluence Furthermore, the C++20 draft (N4860) s7.6.2.1p1 says: The unary * operator performs indirection: the expression to which it is applied shall be a pointer to an object type, or a pointer to a function type and the result is an lvalue referring to the object or function to which the expression points. Without coverity i probably would not have found this copy&paste error. Coverity Scan - Static Analysis The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. Developer Description. Why does Acts not mention the deaths of Peter and Paul? Embedded hyperlinks in a thesis or research paper. So we have to check all the arguments before performing any actions. Otherwise, the result is a pointer to the object or function designated by its operand. return p == NULL || (char *)p < &_etext; VM {} is NOT a viable candidate for solving affinity group violation situation. LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. This check identifies such situation by checking all possible paths where such NULL dereferences can occur. So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). Asking for help, clarification, or responding to other answers. This was potentially problematic, due to the assert on an uninitialized variable. (where the weakness is a quality issue that might indirectly make it easier to introduce security-relevant weaknesses or make them more difficult to detect). 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. May it be expected that the address of operator will eventually be evaluated only after a pointer dereference for a desirable access to a data structure member? If malloc() fails, it returns a null pointer that is assigned to c_str. 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. ImmuniWeb. Dereferencing a null pointer is undefined behavior, typically abnormal program termination. Is there a generic term for these trajectories? 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) FORWARD_NULL. A deferred call's arguments are evaluated immediately, so the defer statement panics due to a nil response. 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. Best to cite C11 s7.24.2.1 here: The memcpy function copies n characters from the object pointed to by s2 into the object pointed to by s1. assert(!invalid(p)); // or whatever, bool invalid(const void *p) { In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Yes -> horrible false positive No -> You removed an important piece of information. In your case you are not doing it,so you have a segmentation fault(or crash) . Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. User without create permission can create a custom object from Managed package using Custom Rest API. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Expressions (EXP), Weaknesses in the 2019 CWE Top 25 Most Dangerous Software Errors, Weaknesses in the 2021 CWE Top 25 Most Dangerous Software Weaknesses, Weaknesses in the 2020 CWE Top 25 Most Dangerous Software Weaknesses, Weaknesses in the 2022 CWE Top 25 Most Dangerous Software Weaknesses, Comprehensive Categorization: Poor Coding Practices, https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf, https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf, https://en.wikipedia.org/wiki/Null_pointer#Null_dereferencing, https://developer.apple.com/documentation/xcode/null-reference-creation-and-null-pointer-dereference, https://www.immuniweb.com/vulnerability/null-pointer-dereference.html, Cybersecurity and Infrastructure Security Agency, Homeland Security Systems Engineering and Development Institute, Null Dereference (Null Pointer Dereference), updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities, updated Common_Consequences, Demonstrative_Examples, Other_Notes, Potential_Mitigations, Weakness_Ordinalities, updated Potential_Mitigations, Relationships, updated Demonstrative_Examples, Description, Detection_Factors, Potential_Mitigations, updated Demonstrative_Examples, Observed_Examples, Relationships, updated Related_Attack_Patterns, Relationships, updated Observed_Examples, Related_Attack_Patterns, Relationships, updated Relationships, Taxonomy_Mappings, White_Box_Definitions, updated Demonstrative_Examples, Observed_Examples, updated Alternate_Terms, Applicable_Platforms, Observed_Examples, updated Demonstrative_Examples, Detection_Factors, References, Relationships. Aaron:I suspect we are talking past each other. Copy the n-largest files from a certain directory to the current one. Why is this claimed dereferencing type-punned pointer warning compiler-specific? A boy can regenerate, so demons eat him for years. Running through Coverity reports and it is having issues with the "onsSelectedCredentials.RemoveAll(x => x.Equals(null));" line here, stating "check_after_deref: Null-checking x suggests that it may be null, but it has already been dereferenced on all paths leading to the check." (I think you cover that in a different rule.) This vulnerability is capable. that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. There are only two condidtions in my code, cond1 and cond2. It was causing glusterd daemon crash for glusterfs. Thanks for the reference to Julia Lawall's response to your question. If an attacker provides an address that appears to be well-formed, but the address does not resolve to a hostname, then the call to gethostbyaddr() will return NULL. 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. If you want to change the value of your pointer, just do var1 = 0; In that case, if you want to change the value of the pointed-to data, well, have the pointer point to some writeable memory first! 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. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. Right? The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. However there is no portable way to verify that the pointer is valid, other than checking for null. I'd guess WG14 has considered these questions, but I haven't until now :). It even looked as a false positive at first. Found logically dead code that would never have been accessed. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. On many platforms, dereferencing a null pointer results inabnormal program termination, but this is not required by the standard. How to force Unity Editor/TestRunner to run at full speed when in background? Thank you for clarifying your assertion until I understood it properly. The two languages try to maximize compatibility, and occasionally succeed. . SSL software allows remote attackers to cause a denial of service (crash) via a crafted SSL/TLS handshake that triggers a null dereference. ', referring to the nuclear power plant in Ignalina, mean? There are other problems with this code, as is noted in the rule. large number of packets leads to NULL dereference, packet with invalid error status value triggers NULL dereference, Chain: race condition for an argument value, possibly resulting in NULL dereference. c - Coverity issue : Explicit Null dereferenced - Stack Overflow We've been getting report on the random crashes, and here it is, the swapped check for index and actual indexed array value. Not the answer you're looking for? Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an address inappropriately aligned for the type of object pointed to, and the address of an object after the end of its lifetime. Why does the narrative change back and forth between "Isabella" and "Mrs. John Knightley" to refer to Emma's sister? Why does this example of what compilers aren't allowed to do cause null pointer dereferencing using cmov? Network monitor allows remote attackers to cause a denial of service (crash) or execute arbitrary code via malformed packets that cause a NULL pointer dereference. This was the kind of error that most likely would never cause a problem during development but could have wreaked havoc after a release. Why don't we use the 7805 for car phone chargers? I'd really love to know why I'm being downvoted. One could argue that all code examples would be redundant with the first pair. One of the Coccinelle software maintainers expressed opposite development views today. rev2023.5.1.43405. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Using LINQ to remove elements from a List