coverity null pointer dereference

More information is available Please edit the custom filter or select a different filter. <, [REF-1031] "Null pointer / Null dereferencing". Isn't easier just to check valid range of length? Possible Null Pointer exception was found in a feature in which I'm the feature owner. Thanks for contributing an answer to Stack Overflow! (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). you are trying to make your var1 to point to the same location as that of var2 and casting it to uint64_t.So from the above two sections var1 and var2 are pointing to NULL pointer ie nothing in simple terms. I'm getting a warning while doing a Static Analysis (SA) on my code. You need to show more code along with what static analysis tool you are using for us to be able to give an answer to you. 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. So we have to check all the arguments before performing any actions. Your assertion is not backed by the wording in the standard, nor by common implementer understanding. Chain - a Compound Element that is a sequence of two or more separate weaknesses that can be closely linked together within software. VM {} is NOT a viable candidate for solving affinity group violation situation. *var1 = 0; this dereferences the pointer, i.e. 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. This fixed weird behaviour that was really hard to find. I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. Why don't we use the 7805 for car phone chargers? NIST Workshop on Software Security Assurance Tools Techniques and Metrics. }. What's the cheapest way to buy out a sibling's share of our parents house if I have no cash and want to pay less than the appraised value? And Coverity will tend to interpret your code rather than reading your mind. Common logic to perform in the middle? Not the answer you're looking for? Avast and AVG Antivirus for Windows were susceptible to a NULL pointer dereference issue via RPC-interface. The NULL check is unnecessary because the pointer can't be NULL, so the NULL check should be removed. Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. Why does Acts not mention the deaths of Peter and Paul? The article easily misleads the reader into believeing that ensuring pointer validity boils down to checking for pointer being not equal to NULL. However, I must add a few qualifications: First of all, there is the question of whether this is for C or for C++. Dates. Making statements based on opinion; back them up with references or personal experience. Description. Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. in this line you are trying to assign a value 0 to a location pointed by var1 which is NUll location ie invalid address and de-referencing a invalid /Null address will result in crash. A boy can regenerate, so demons eat him for years. A pointer should be made to point to some valid memory location before writing something to it. We should Zoom if you wish to talk more. rev2023.5.1.43405. ', referring to the nuclear power plant in Ignalina, mean? Copy the n-largest files from a certain directory to the current one. This bug was quite hard to spot! To learn more, see our tips on writing great answers. It evaluates to true if a_ptr is not NULL. "Signpost" puzzle from Tatham's collection. that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. . The issue was fixed with Avast and AVG Antivirus version 22.11 Publish Date : 2023-04-19 Last Update Date : 2023-04-19 Collapse All Expand All Select Select&Copy Scroll To Vendor . Copyright 20062023, The MITRE Corporation. NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. second, a de-reference of that variable. What's the rationale for null terminated strings? Standing by. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. . NULL can't point to data. Can this be fixed if I reassign the *var1 to NULL again ?? CPE Name Name Version; mruby: 3.1.0: Products. Search for vulnerabilities resulting from the violation of this rule on the CERT website. Buffer overflow difficult to find by reading the code that would result a crash if path is too long. I'm learning and will appreciate any help, Embedded hyperlinks in a thesis or research paper. Which language's style guidelines should be used when writing code that is supposed to be called from another language? 2005-11-07. 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). Even documented "we don't need to care, I think" issue can become an issue when one does not check the background implementation. This was the kind of error that most likely would never cause a problem during development but could have wreaked havoc after a release. It is always true that if E is a function designator or an lvalue that is a valid operand of the unary & operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. 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? Making statements based on opinion; back them up with references or personal experience. Synopsys, Inc. | Policy Statement | Contact, // Create a set of all VMs in affinity groups, // There is no need to migrate when no collision was detected. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Not sure if this is directly related to the error/warning you get but in general I think you should rather use, C# Coverity giving "Dereference before null check (REVERSE_INULL)" on a RemoveAll call to remove null entries from a list, How a top-ranked engineering school reimagined CS curriculum (Ep. Possibly Clang/LLVM may choose to always return a valid value for &NULL->member. 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. Asking for help, clarification, or responding to other answers. *var1 = 0; this dereferences the pointer, i.e. Unless explicitly stated otherwise in the description of a particular function in this subclause, pointer arguments on such a call shall still have valid values, as described in 7.1.4. In some situations, however, dereferencing a null pointer can lead to the execution of arbitrary code [Jack 2007,van Sprundel 2006]. . You probably don't understand that the * in a pointer declaration and the * in a pointer arithmetics expression mean completely opposite things. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things. <, [REF-1033] "NULL Pointer Dereference [CWE-476]". Typical "easy to spot if you know there is a problem error". Loading. Asking for help, clarification, or responding to other answers. Unless explicitly stated otherwise in the description of a particular function in this subclause, pointer arguments on such a call shall still have valid values, as described in 7.1.4. What is the symbol (which looks similar to an equals sign) called? 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. I'll add that right now, but I feel it's pointless, since it will only clutter up the question. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc. Using platform-specific means (e.g. 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. The purpose of that line of code is to read through the current values in the list and strip out any that have become null, there's no null check happening as far as I can tell. How a top-ranked engineering school reimagined CS curriculum (Ep. Category. This check identifies such situation by checking all possible paths where such NULL dereferences can occur. Hence the error. Carnegie Mellon University The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. See C23 (n3096) s6.5.3.2p3: The unary & operator yields the address of its operand. DATABASE RESOURCES PRICING ABOUT US. race condition causes a table to be corrupted if a timer activates while it is being modified, leading to resultant NULL dereference; also involves locking. Markus:AFAICT the respponses to this StackOverflow question agree with my previous assertions. This means one of two things: The pointer could in fact be NULL and any dereference prior to that NULL check could result in a NULL pointer dereference, so you need to either do the NULL check sooner or don't deereference at that point. Either the check against null is unnecessary, or there may be a null pointer dereference. Optimizers are optimizing based on this latitude and have been for years. More specific than a Base weakness. Which language's style guidelines should be used when writing code that is supposed to be called from another language? For users who are mapping an issue to CWE/CAPEC IDs, i.e., finding the most appropriate CWE for a specific issue (e.g., a CVE record). Why did DOS-based Windows require HIMEM.SYS to boot? (C11, S7.24.2.1). Why are players required to record the moves in World Championship Classical games? So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Network monitor allows remote attackers to cause a denial of service (crash) via a malformed RADIUS packet that triggers a null dereference. 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. In 5e D&D and Grim Hollow, how does the Specter transformation affect a human PC in regards to the 'undead' characteristics and spells? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Asside - I would suggest initialising your pointers to, It's impossible to tell from that code whether. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Canadian of Polish descent travel to Poland with Canadian passport. If all pointers that could have been modified are sanity-checked previous to use, nearly all NULL pointer dereferences can be prevented. Believing that dereferencing NULL shouldn't crash the system doesn't make it true. Right? Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. Base - a weakness Extended Description NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. 2012-09-11. Note that this code is also vulnerable to a buffer overflow (CWE-119). Various developers and code reviewers are struggling also with evolution of the specifications for such programming languages. In this scenario, by the time, I come in 'cond2', I already have 'q' set. New feature implementation got stuck for days because old code had obscure implementation which caused debuging nightmare. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. "Signpost" puzzle from Tatham's collection, Image of minimal degree representation of quasisimple group unique up to conjugacy. 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. How to force Unity Editor/TestRunner to run at full speed when in background? Is there any known 80-bit collision attack? That makes sense. 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. It is kind of funny, though. If your code examples are simply searching for instances of C code of this nature. 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. In your code example, the p1my_item will be evaluated before t he & operator, and so this rule is violated, although you are really trying to do pointer arithmetic rather than see what the pointer points to. Example: tool developers, security researchers, pen-testers, incident response analysts. Pittsburgh, PA 15213-2612 that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Variable "var" was uninitialized, then function that was supposed to fill it in was called. Now it seems that I can inform also Linux contributors with higher confidence about further change possibilities (which I detected by the means of the Coccinelle software again recently). Possible Null Pointer exception was found in a feature in which I'm the feature owner. 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! Connect and share knowledge within a single location that is structured and easy to search. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore. At this point we define size as strlen(input_str) + 1. If you are working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the if statement; and unlock when it has finished. If copying takes place between objects that overlap, the behavior is undefined. * Select VMs from the broken affinity group that are running on the same host. 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. Ah, gotcha. I've posted an example for the sake of completion-. It worked normally, but sometimes devices had cryptic types. I'll just provide a few references to back up my beliefs. CWE, CWSS, CWRAF, and the CWE logo are trademarks of The MITRE Corporation. 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. Customer's opinion is that it is always a good practice to check a pointer for a NULL Value before freeing it. Similarly, if the operand is the result of a [] operator, neither the & operator nor the unary * that is implied by the [] is evaluated and the result is as if the & operator were removed and the [] operator were changed to a + operator. To fix the bug in the code and also make Coverity happy, as suggested by derHugo in a comment, change the RemoveAll line to something like this: Thanks for contributing an answer to Stack Overflow! {"serverDuration": 277, "requestCorrelationId": "e2a1d936a1543fbd"}, EXP34-C. Do not dereference null pointers, Clever Attack Exploits Fully-Patched Linux Kernel, ERR33-C. Detect and handle standard library errors, one compliant and one non-compliant example, CERT Oracle Secure Coding Standard for Java, EXP01-J. Off by one error: It is the third example. This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. In Coverity, FORWARD_NULL reports defects when there are enough evidences to be sure the null access will (can) happen. 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. I reordered that code example to do all the checks before allocations. Coverity complains below message: CID 25469 (#1 of 1): Explicit null dereferenced (FORWARD_NULL) 9. var_deref_op: Dereferencing null pointer q. I do not understand why coverity complains here. Aaron:I suspect we are talking past each other. Find centralized, trusted content and collaborate around the technologies you use most. What is this brick with a round back and a stud on the side used for? Allowing it to be removed. Assign an array of Swift strings to a C structure variable taking a char ** value. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). . Can corresponding author withdraw a paper after it has accepted without permission/acceptance of first author. It does not give the pointer a new value. The choice could be made to use a language that is not susceptible to these issues. Would My Planets Blue Sun Kill Earth-Life? That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. WG21 (the C++ working group) may wish to define 0->y, and they are within their right to do so. Generating points along line with specifying the origin of point generation in QGIS. When the URL is not present, the call to getStringExtra() will return null, thus causing a null pointer exception when length() is called. 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. Without coverity i probably would not have found this copy&paste error. Coverity Collector User Votes: 0 Vote for this issue Watchers: 1 Start watching this issue. The correct idiom is to only allocate storage if the pointer is currently NULL. 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. The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. For users who want to customize what details are displayed. I would, at the very least, put an assert(q) inside if (code2), but: Ideally you'd stick with that one if/else and put all your logic in there. Identify error conditions that are not likely to occur during normal usage and trigger them. It also permits &x[y] to translate to x + y, but that is still UB if x is null because of ARR38-C. ISO C just has no similar wording for x->member. NIST. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); Security Intelligence; Non-intrusive assessment; Developers SDK; Database . This is in the key management code which converts passwords. Embedded hyperlinks in a thesis or research paper. Chains can involve more than two weaknesses, and in some cases, they might have a tree-like structure. How do the interferometers on the drag-free satellite LISA receive power without altering their geodesic trajectory? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. Chat client allows remote attackers to cause a denial of service (crash) via a passive DCC request with an invalid ID number, which causes a null dereference. Why does the narrative change back and forth between "Isabella" and "Mrs. John Knightley" to refer to Emma's sister? If code1 and code2 may both be true, though, then you do have a substantial bug here. 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. This bug ONLY surfaces when debugging or running the program with her verbosity. If your code examples are simply searching for instances of C code of this nature, then the UB is not in your code, you just may be searching for code with potential UB. An extremely nice thing which was discovered only by Coverity. mruby is vulnerable to NULL Pointer. Coverity scan helps our developers finding issues like these. Network monitor allows remote attackers to cause a denial of service (crash) via a malformed Q.931, which triggers a null dereference. What REALLY happens when you don't free after malloc before program termination? The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results. This warning thrown by Coverity if you dereference a pointer and then later on do a NULL check on it. Full description here: http://curl.haxx.se/docs/adv_20150617B.html It could make a malicious server fool a client to send off data from Prototypical copy-paste error. 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. 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. If an invalid value has been assigned to the pointer, the behavior of the unary * operator is undefined.115). And in this case, there is no pointed-to data. /** 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. There are other problems with this code, as is noted in the rule. Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? If you want to change the value of your pointer, just do var1 = 0; This code also violates ERR33-C. Detect and handle standard library errors. but we still consider it a violation of this rule for practicality, although to be anal, it is instead a violation of ARR30-C. 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 believe in this case, either expression would work. EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. Software Engineering Institute LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. 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. This means one of two things: In this particular case, you're explicitly setting a_ptr to the address of a variable, so it can't possibly be NULL at that point. Separate it into a different function that you can call. Are these quarters notes or just eighth notes? Example: educators, technical writers, and project/program managers. The added benefit of this is that you probably no longer require both p and q and so the entire function becomes far more lean.

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