The article easily misleads the reader into believeing that ensuring pointer validity boils down to checking for pointer being not equal to NULL. :). }. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. I'm getting a warning while doing a Static Analysis (SA) on my code. Can corresponding author withdraw a paper after it has accepted without permission/acceptance of first author. and Gary McGraw. accesses memory stored at its address. Find centralized, trusted content and collaborate around the technologies you use most. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In your case you are not doing it,so you have a segmentation fault(or crash) . * @param affinityGroup broken affinity rule 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. To learn more, see our tips on writing great answers. 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. Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). Coverity Collector User Votes: 0 Vote for this issue Watchers: 1 Start watching this issue. Right? Typical "easy to spot if you know there is a problem error". It evaluates to true if a_ptr is not NULL. Phew, we're agreed here. "Signpost" puzzle from Tatham's collection. 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). 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. Connect and share knowledge within a single location that is structured and easy to search. Consider the following example of a typical client server exchange. In this scenario, by the time, I come in 'cond2', I already have 'q' set. then the UB is not in your code, you just may be searching for code with potential UB. 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. This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. If malloc() fails, it returns a null pointer that is assigned to c_str. <<< CID 102061: Null pointer dereferences REVERSE_INULL <<< Null-checking " doc_bv " suggests that it may be null, but it has already been dereferenced on all paths leading to the check. If an attacker can control the program's environment so that "cmd" is not defined, the program throws a NULL pointer exception when it attempts to call the trim() method. The NULL check is unnecessary because the pointer can't be NULL, so the NULL check should be removed. And in this case, there is no pointed-to data. 2021-12-15T00:00:00 Description. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. rev2023.5.1.43405. Simple and excellent job. 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. It looks like a logic bug, which can cause a memory leaking. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Making statements based on opinion; back them up with references or personal experience. Good question! Identify error conditions that are not likely to occur during normal usage and trigger them. Thanks for the reference to Julia Lawall's response to your question. 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. Possible Null Pointer exception was found in a feature in which I'm the feature owner. * Asking for help, clarification, or responding to other answers. Coverity issue : Explicit Null dereferenced, How a top-ranked engineering school reimagined CS curriculum (Ep. NIST. The platform does add offsetof( struct_type, member) to input and dereferences that. The code processes a physics modification option line given either from the command line or file. CPE Name Name Version; mruby: 3.1.0: Products. 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. Checker. First if executes for cond1 and else executes for cond2.. Only one of them could be true at a time. Do you find another previous clarification approach interesting and helpful? This code also violates ERR33-C. Detect and handle standard library errors. Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. What is it that I did not understand? And in this step. 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. This HandleRequest Function evaluates the close before checking the error. patch id. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. of making the mruby interpreter crash, thus affecting the. 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. NULL can't point to data. Variable "var" was uninitialized, then function that was supposed to fill it in was called. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. That exception could have rendered the entire feature non operational (And many log messages that the user wouldn't understand). Various developers and code reviewers are struggling also with evolution of the specifications for such programming languages. At best ISO C is under-specified in this regard, and perhaps should explicitly say so. Common logic to perform in the middle? 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! 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? In the complaint version, I like to make source code checking a little quicker by putting parenthesizes around arguments to |= or &= as. This solution also ensures that theuser_data pointer is not null. rev2023.5.1.43405. Chains can involve more than two weaknesses, and in some cases, they might have a tree-like structure. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. How do the interferometers on the drag-free satellite LISA receive power without altering their geodesic trajectory? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Buffer overflow and possibly corrupting the module database. Before assigning a value you need to allocate a memory and make the pointers to point to that memory location and then assign a value. What is the symbol (which looks similar to an equals sign) called? Buffer overflow difficult to find by reading the code that would result a crash if path is too long. .. Would it be ok if I write !cond1 just like this: Logically, based on what you've said, and assuming that code1 and code2 are mutually exclusive, this is a false positive. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I added an assertion to that compliant code example. Canadian of Polish descent travel to Poland with Canadian passport. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). But no where in that particular idiom would a NULL pointer necessarily be deferenced. Ah, gotcha. Thus I became a bit more curious about involved technical details. We've been getting report on the random crashes, and here it is, the swapped check for index and actual indexed array value. 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. Monitor the software for any unexpected behavior. with solve of this bug problems have gone. Can this be fixed if I reassign the *var1 to NULL again. Base - a weakness 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. It seems that my understanding needs also to grow for such information. The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. What is the symbol (which looks similar to an equals sign) called? int changed to size_t and if size_t parameter's is zero, allocate one word. Security Intelligence; Non-intrusive assessment; Developers SDK; Database . It also adds assertions to document that certain other pointers must not be null. Is it safe to publish research papers in cooperation with Russian academics? This error detected by CoverityScan detected a case where the driver would never run at the maximum CPI clock speed. Example: tool developers, security researchers, pen-testers, incident response analysts. 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. Not the answer you're looking for? 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. Variant - a weakness Allowing it to be removed. The occurrence of this wrong index was not seen in the code. 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. VM {} is a viable candidate for solving affinity group violation situation. Either the check against null is unnecessary, or there may be a null pointer dereference. It can never evaluate to true (unless Equals has been overridden to do something screwy). SSL software allows remote attackers to cause a denial of service (crash) via a crafted SSL/TLS handshake that triggers a null dereference. How a top-ranked engineering school reimagined CS curriculum (Ep. 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. 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). Possible Null Pointer exception was found in a feature in which I'm the feature owner. Coverity complains below message: I do not understand why coverity complains here. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. * Select VMs from the broken affinity group that are running on the same host. It could cause e-mails stored with incorrect names. You have defined pointers var1 and var2 of type uint64_t and char respectively which are pointing to NULL . 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. Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). Game allows remote attackers to cause a denial of service (server crash) via a missing argument, which triggers a null pointer dereference. But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. What REALLY happens when you don't free after malloc before program termination? 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. 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. That interpretation of the standard is not supported universally. Example: educators, technical writers, and project/program managers. When the URL is not present, the call to getStringExtra() will return null, thus causing a null pointer exception when length() is called. See C23 (n3096) s6.5.3.2p3: The unary & operator yields the address of its operand. Category. 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 compliant solution ensures that the pointer returned by png_malloc() is not null. This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. 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. http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html. LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. Without coverity i probably would not have found this copy&paste error. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. Not the answer you're looking for? 33615. I got the impression that 31 source files of Linux modules will need further adjustments. 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. So the SIZE_MAX check was unnecessary. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. What is this brick with a round back and a stud on the side used for? I reordered that code example to do all the checks before allocations. My guess is it is telling you "you are doing the NULL check now, but you have already dereferenced it before. Made code more compliant with other rules. Search for vulnerabilities resulting from the violation of this rule on the CERT website. Correct; a null pointer is not a valid pointer for the C library functions. <, [REF-18] Secure Software, Inc.. "The CLASP Application Security Process". When this happens, CWE refers to X as "primary" to Y, and Y is "resultant" from X. 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]. The two languages try to maximize compatibility, and occasionally succeed. Coverity is giving you a warning because you are in fact doing a NULL check: Here, a_ptr is evaluated in a boolean context. The correct idiom is to only allocate storage if the pointer is currently NULL. An extremely nice thing which was discovered only by Coverity. And in this case, there is no pointed-to data. I've posted an example for the sake of completion-. There are other problems with this code, as is noted in the rule.
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