This one is pretty awesome. View - a subset of CWE entries that provides a way of examining CWE content. first, a null assignment, or a comparison with null will give Coverity an evidence to believe the variable could be null. Copy the n-largest files from a certain directory to the current one. This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. * Category - a CWE entry that contains a set of other entries that share a common characteristic. ROSE does not handle cases where an allocation is assigned to an lvalue that is not a variable (such as a struct member or C++ function call returning a reference), Finds instances where a pointer is checked against NULL and then later dereferenced, Identifies functions that can return a null pointer but are not checked, Identifies code that dereferences a pointer and then checks the pointer against NULL, Can find the instances where NULL is explicitly dereferenced or a pointer is checked againstNULL but then dereferenced anyway. Find centralized, trusted content and collaborate around the technologies you use most. In your case you are not doing it,so you have a segmentation fault(or crash) . Find centralized, trusted content and collaborate around the technologies you use most. A boy can regenerate, so demons eat him for years. I see coverity defect with bold/italic code. * @param affinityGroup broken affinity rule I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. rev2023.5.1.43405. NULL can't point to data. What is the symbol (which looks similar to an equals sign) called? NIST Workshop on Software Security Assurance Tools Techniques and Metrics. There are other problems with this code, as is noted in the rule. If malloc() fails, it returns a null pointer that is assigned to c_str. Find centralized, trusted content and collaborate around the technologies you use most. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. EXP34-C. Do not dereference null pointers - Confluence Improve INSERT-per-second performance of SQLite. The code is dead and will be never processed because 'decoded' outside the scope and redefined in local. Interpreting non-statistically significant results: Do we have "no evidence" or "insufficient evidence" to reject the null? Expressions (EXP), SEI CERT C Coding Standard - Guidelines 03. If you put the code above in a c file, run the analysis, does it report the warning? If all pointers that could have been modified are sanity-checked previous to use, nearly all NULL pointer dereferences can be prevented. This table shows the weaknesses and high level categories that are related to this weakness. Coverity Scan - Static Analysis Would My Planets Blue Sun Kill Earth-Life? FORWARD_NULL. In Coverity, FORWARD_NULL reports defects when there are enough evidences to be sure the null access will (can) happen. But passing 0 to memcpy() is not one of them. But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. uint64_t *var1 = NULL; this declares a uint64_t pointer (type uint64_t*). It should be an ingrained practice. Chains can involve more than two weaknesses, and in some cases, they might have a tree-like structure. Assign an array of Swift strings to a C structure variable taking a char ** value. VM {} is NOT a viable candidate for solving affinity group violation situation. How come an array's address is equal to its value in C? This rule applies to all null pointers, regardless of which function returned them. The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. No affinity group collision detected for cluster {}. Coverity - forward null dereference #1747 - Github I've changed it to say null pointer instead of invalid pointer. What's the rationale for null terminated strings? 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. uint64_t *var1 = malloc(sizeof(uint64_t)); /* Allocate memory for one uint64_t on the heap and set var1 to point at it */. Pointer members in structs are not checked. Thanks for contributing an answer to Stack Overflow! 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). Coverity Collector User Votes: 0 Vote for this issue Watchers: 1 Start watching this issue. Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? Why does the narrative change back and forth between "Isabella" and "Mrs. John Knightley" to refer to Emma's sister? The expression x.Equals(null) will throw NullReferenceException if x is null. <, [REF-18] Secure Software, Inc.. "The CLASP Application Security Process". rev2023.5.1.43405. 2019-07-15. Unexpected behavior can be pain to hunt down when one of these is involved. Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). Loading. Configure coverity to check that a declared variable is initialized before usage as a pointer. While there are no complete fixes aside from conscientious programming, the following steps will go a long way to ensure that NULL pointer dereferences do not occur. When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. Why don't we use the 7805 for car phone chargers? We didn't figure ourselves where those threading issues came from and tried to hide them with hacks. Setting an incorrect jump target leads to a certain crash if the code is exercised. 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. I have simplified it below (with the first warning)-, The code goes on to do several operations with a_ptr. You probably don't understand that the * in a pointer declaration and the * in a pointer arithmetics expression mean completely opposite things. REVERSE_INULL False Positive "Dereference before NULL check" Not the answer you're looking for? Could I capture, and I would be able to glean much security information from the dump? This bug was quite hard to spot! Event var_deref_model: | Passing null pointer "master_uri_env" to "operator =", which dereferences it. Many modern techniques use data flow analysis to minimize the number of false positives. The occurrence of this wrong index was not seen in the code. I would therefore assert that a platform whose memcpy() did anything besides a no-op when given n=0 and valid source/destination pointers was not C-standards-compliant. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. rev2023.5.1.43405. It evaluates to true if a_ptr is not NULL. Why did DOS-based Windows require HIMEM.SYS to boot? The user_data pointer could be invalid in other ways, such as pointing to freed memory. 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. Solution 1, it looks like, today's solution tomorrow's problem. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. It even looked as a false positive at first. Found logically dead code that would never have been accessed. When this happens, CWE refers to X as "primary" to Y, and Y is "resultant" from X. Thanks for the reference to Julia Lawall's response to your question. Which language's style guidelines should be used when writing code that is supposed to be called from another language? 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 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. 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. Optimizers are optimizing based on this latitude and have been for years. Since the code does not check the return value from gethostbyaddr (CWE-252), a NULL pointer dereference (CWE-476) would then occur in the call to strcpy(). Why does this example of what compilers aren't allowed to do cause null pointer dereferencing using cmov? 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 choice could be made to use a language that is not susceptible to these issues. These types of problems usually lead to insidious correctness errors since exceptions are caught at a higher level. Separate it into a different function that you can call. Right? 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. In the following code, the programmer assumes that the system always has a property named "cmd" defined. 0->member is undefined behavior. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results. However, I must add a few qualifications: First of all, there is the question of whether this is for C or for C++. Thank you for clarifying your assertion until I understood it properly. How do the interferometers on the drag-free satellite LISA receive power without altering their geodesic trajectory? Avast and AVG Antivirus for Windows were susceptible to a NULL pointer dereference issue via RPC-interface. It is pretty easy to miss such things when adding a new feature. Standing by. 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. 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). Unfortunately, your link also points to code that violates this rule, and is thus undefined behavior. mruby is vulnerable to NULL Pointer Dereference Affected Software. then the UB is not in your code, you just may be searching for code with potential UB. How to force Unity Editor/TestRunner to run at full speed when in background? Connect and share knowledge within a single location that is structured and easy to search. 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. I'll add that right now, but I feel it's pointless, since it will only clutter up the question. Identify error conditions that are not likely to occur during normal usage and trigger them. But no where in that particular idiom would a NULL pointer necessarily be deferenced. 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. If the operand has type "type", the result has type "pointer to type". In my experience, there are reasons to check for a NULL pointer other than dereferencing it. I reordered that code example to do all the checks before allocations. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. ), [REF-6] Katrina Tsipenyuk, Brian Chess 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. If your code examples are simply searching for instances of C code of this nature. 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. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? 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. 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. This has been there for decade, and was shipped in a real product. I'm sorry if I have misunderstood the intent in your question. Dereferencing a null pointer is undefined behavior. To learn more, see our tips on writing great answers. The platform does add offsetof( struct_type, member) to input and dereferences that.