coverity null pointer dereference

NIST Workshop on Software Security Assurance Tools Techniques and Metrics. My guess is it is telling you "you are doing the NULL check now, but you have already dereferenced it before. Configure coverity to check that a declared variable is initialized before usage as a pointer. 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. This is in the key management code which converts passwords. If it wasn't for coverity Resource leaks: I hate them, especially in libc, which is code you expect to be hot. Our code base contains a lot of copy paste mistakes, we are glad that there is a tool like coverity that can help to detect them. The n=0 is a mildly interesting edge case: Clearly a pointer that points to at least one valid byte could be used as the src or dest pointer to a call to memcpy(, 0). It does not give the pointer a new value. 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." Hence the error. This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. How to remove elements from a generic list while iterating over it? I added a comment to explain that SIZE_MAX is the limit of size_t. This fault is buried deep within some complex logic that makes it really hard to track. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Will the ordering matter a bit more for the safe evaluation of involved expressions? Setting an incorrect jump target leads to a certain crash if the code is exercised. NULL Pointer Dereference in mrb_vm_exec with super in GitHub. At best ISO C is under-specified in this regard, and perhaps should explicitly say so. That exception could have rendered the entire feature non operational (And many log messages that the user wouldn't understand). Variable "var" was uninitialized, then function that was supposed to fill it in was called. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. What is it that I did not understand? However there is no portable way to verify that the pointer is valid, other than checking for null. 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. CWE is sponsored by the U.S. Department of Homeland Security (DHS) Cybersecurity and Infrastructure Security Agency (CISA) and managed by the Homeland Security Systems Engineering and Development Institute (HSSEDI) which is operated by The MITRE Corporation (MITRE). accesses memory stored at its address. ssh component for Go allows clients to cause a denial of service (nil pointer dereference) against SSH servers. Thanks for contributing an answer to Stack Overflow! It is kind of funny, though. Did the drapes in old theatres actually say "ASBESTOS" on them? Either the check against null is unnecessary, or there may be a null pointer dereference. Off by one error: It is the third example. Markus:Unfortunately, your link also points to code that violates this rule, and is thus undefined behavior. Only irrelevant information has been removed. Would My Planets Blue Sun Kill Earth-Life? 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. This is a matter of style, and also following code walkthrough. For users who are concerned with the practical application and details about the nature of a weakness and how to prevent it from happening. Find centralized, trusted content and collaborate around the technologies you use most. (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). This pointer was the resaon of a memory leak Realy nice catch by Coverity. Ubuntu won't accept my choice of password, Passing negative parameters to a wolframscript, Folder's list view has different sized fonts in different folders, Image of minimal degree representation of quasisimple group unique up to conjugacy. it may still not be enough to satisfy Coverity. Dereferencing a null pointer is undefined behavior. I suggest that this topic needs to include calloc() and realloc() Refer to Linux man pages online for more enlightenment about malloc(), and friends. Apple. If the operand is the result of a unary * operator, neither that operator nor the & operator is evaluated and the result is as if both were omitted, except that the constraints on the operators still apply and the result is not an lvalue. Explicitly initialize all your variables and other data stores, either during declaration or just before the first usage. Finding the distance from a corner of a cube to the midpoint of an edge. Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. Canadian of Polish descent travel to Poland with Canadian passport. then the UB is not in your code, you just may be searching for code with potential UB. The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. For example, run the program under low memory conditions, run with insufficient privileges or permissions, interrupt a transaction before it is completed, or disable connectivity to basic network services such as DNS. Making statements based on opinion; back them up with references or personal experience. This does not have any impact, because it is just an assert. Relatively low, but also relatively hilarious - someone decided to "shut up" a GCC warning in 2006 by putting parentheses around an assignment used as a truth value, but misplaced Impact is low, just wanted to commend you! Assign an array of Swift strings to a C structure variable taking a char ** value. In this scenario, by the time, I come in 'cond2', I already have 'q' set. I would also guess that pointers that point to the one-past-the-end of an array are also invalid. It would have been terrible to A simple decrement that wraps around causing an array overflow on lsm->lsm_oinfo[i[. I'll just provide a few references to back up my beliefs. The two languages try to maximize compatibility, and occasionally succeed. Unexpected behavior can be pain to hunt down when one of these is involved. I'd guess null pointers are not valid, even though they point to 0 bytes. 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. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation. IMHO, the rule title should be changed to something less general. first, a null assignment, or a comparison with null will give Coverity an evidence to believe the variable could be null. This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. That's true. repository mruby/mruby prior to 3.2. New feature implementation got stuck for days because old code had obscure implementation which caused debuging nightmare. 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. But no where in that particular idiom would a NULL pointer necessarily be deferenced. 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). A pointer should be made to point to some valid memory location before writing something to it. No affinity group collision detected for cluster {}. Wikipedia. Asking for help, clarification, or responding to other answers. But passing 0 to memcpy() is not one of them. This information is often useful in understanding where a weakness fits within the context of external information sources. That makes sense. Carnegie Mellon University This bug ONLY surfaces when debugging or running the program with her verbosity. Game allows remote attackers to cause a denial of service (server crash) via a missing argument, which triggers a null pointer dereference. Parabolic, suborbital and ballistic trajectories all follow elliptic paths. More specific than a Pillar Weakness, but more general than a Base Weakness. Image of minimal degree representation of quasisimple group unique up to conjugacy. Dereferencing a pointer that might be null " findVmViolatingPositiveAg(affinityGroup, vmToHost) " when calling " getVmsByIds . 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. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. I've changed it to say null pointer instead of invalid pointer. Negative index used in the code could result in a totally wrong behavior in the application. Good question! How to force Unity Editor/TestRunner to run at full speed when in background? . Identify error conditions that are not likely to occur during normal usage and trigger them. Yes -> horrible false positive No -> You removed an important piece of information. What are the arguments for/against anonymous authorship of the Gospels, Two MacBook Pro with same model number (A1286) but different year, Simple deform modifier is deforming my object. The format With two string literals, "SGI_ACL_FILE" and "SGI_ACL_DEFAULT", the addition of the (unsigned char *) cast resulted in sizeof returning 7 (size of pointer minus one), rather than the length of Impacts a highly used used area of our code which could cause problems when running for extended time. Pointer members in structs are not checked. 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. patch id. Embedded hyperlinks in a thesis or research paper, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A). Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. As a result, the optimizer may remove null . Specifically, it understands that Equals is meant to test equality, and that you're comparing x to null as if they might be the same (the "check"), but you can't get into Equals (the "path") at all because of the NullReferenceException. What is this brick with a round back and a stud on the side used for? void host_lookup(char *user_supplied_addr){, if("com.example.URLHandler.openURL".equals(intent.getAction())) {. The user_data pointer could be invalid in other ways, such as pointing to freed memory. Simple and excellent job. Hence the error. And this error has been in the codebase for the last 9 Coverty scan correctly understood the logic of this code, and reported that the loop condition is wrong. This fixed weird behaviour that was really hard to find. unity3d - C# Coverity giving "Dereference before null check (REVERSE Various developers and code reviewers are struggling also with evolution of the specifications for such programming languages. 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. 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! Null pointer dereferences: This code will definitely crash due to a null pointer dereference in certain cases.. View Defect : wazuh/ossec-wazuh: USE_AFTER_FREE: C/C++: Memory - illegal accesses: This pointer was the resaon of a memory leak. Chains can involve more than two weaknesses, and in some cases, they might have a tree-like structure. Chain - a Compound Element that is a sequence of two or more separate weaknesses that can be closely linked together within software. The HandleRequest function is intended to perform a request and use a defer to close the connection whenever the function returns. What's the rationale for null terminated strings? 4500 Fifth Avenue The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. Identify all variables and data stores that receive information from external sources, and apply input validation to make sure that they are only initialized to expected values.

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