Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. It can never evaluate to true (unless Equals has been overridden to do something screwy). This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. Buffer overflow difficult to find by reading the code that would result a crash if path is too long. What should I follow, if two altimeters show different altitudes? CPE Name Name Version; mruby: 3.1.0: Products. Is this a false positive from Coverity or should I do something to fix this? * Select VMs from the broken affinity group that are running on the same host. Making statements based on opinion; back them up with references or personal experience. May be you need to do this null check much before. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. Would you like to help any further according to different understanding and expectations for affected implementation details. In this scenario, by the time, I come in 'cond2', I already have 'q' set. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. It seems that my understanding needs also to grow for such information. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. ), [REF-6] Katrina Tsipenyuk, Brian Chess Markus:Unfortunately, your link also points to code that violates this rule, and is thus undefined behavior. mruby is vulnerable to NULL Pointer. 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. 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. (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). 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. Making statements based on opinion; back them up with references or personal experience. This listing shows possible areas for which the given weakness could appear. I've changed it to say null pointer instead of invalid pointer. However, I must add a few qualifications: First of all, there is the question of whether this is for C or for C++. What's the rationale for null terminated strings? SSL software allows remote attackers to cause a denial of service (crash) via a crafted SSL/TLS handshake that triggers a null dereference. This turned out to be a security flaw, now known as CVE-2015-3237. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. Category - a CWE entry that contains a set of other entries that share a common characteristic. Dereferencing a null pointer is undefined behavior. Good question! My guess is it is telling you "you are doing the NULL check now, but you have already dereferenced it before. Consider the following example of a typical client server exchange. Using platform-specific means (e.g. 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. 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? Horizontal and vertical centering in xltabular. COVERITY checker description | The STAR experiment 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. Coverity analysis defect 116994: Dereference after null check - MongoDB <<< 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. patch id. I think that checking for user_data being NULL would be an improvement to the CS so long as there is an explicit mention that user_data being NULL is invalid even if length == 0. Right? Find centralized, trusted content and collaborate around the technologies you use most. Is it safe to publish research papers in cooperation with Russian academics? DATABASE RESOURCES PRICING ABOUT US. If the operand has type "type", the result has type "pointer to type". I'll add that right now, but I feel it's pointless, since it will only clutter up the question. 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(). You have defined pointers var1 and var2 of type uint64_t and char respectively which are pointing to NULL . In your case you are not doing it,so you have a segmentation fault(or crash) . Coverity complains below message: I do not understand why coverity complains here. Note that this code is also vulnerable to a buffer overflow (CWE-119). This error detected by CoverityScan detected a case where the driver would never run at the maximum CPI clock speed. 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 find it interesting in this case how you think in another direction. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. The value 0 for the number of bytes to copy is not what causes the UB, it's the null pointer value which triggers it. "Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors". 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. Are these quarters notes or just eighth notes? To learn more, see our tips on writing great answers. There are other problems with this code, as is noted in the rule. 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! <, [REF-1033] "NULL Pointer Dereference [CWE-476]". It should be an ingrained practice. Chain - a Compound Element that is a sequence of two or more separate weaknesses that can be closely linked together within software. Optimizers are optimizing based on this latitude and have been for years. When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. * @return a list of vms which are candidates for migration Thus I became a bit more curious about involved technical details. If all pointers that could have been modified are sanity-checked previous to use, nearly all NULL pointer dereferences can be prevented. NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. Unfortunately the problem is much more complex, and generally unsolvable within standard C. Consider the following example: There's no way f can check whether x points into valid memory or not. 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. Shouldn't the function check all pointers before dereferencing them or passing them to another function? CVE-2023-1587 : Avast and AVG Antivirus for Windows were susceptible to 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. It even looked as a false positive at first. Found logically dead code that would never have been accessed. It worked normally, but sometimes devices had cryptic types. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore. NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Thanks for contributing an answer to Stack Overflow! What REALLY happens when you don't free after malloc before program termination? Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? Various developers and code reviewers are struggling also with evolution of the specifications for such programming languages. 2012-09-11. This table specifies different individual consequences associated with the weakness. In Coverity, FORWARD_NULL reports defects when there are enough evidences to be sure the null access will (can) happen. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. "Signpost" puzzle from Tatham's collection, Image of minimal degree representation of quasisimple group unique up to conjugacy. it may still not be enough to satisfy Coverity. Agreed. then the UB is not in your code, you just may be searching for code with potential UB. It would have been terrible to A simple decrement that wraps around causing an array overflow on lsm->lsm_oinfo[i[. This code also violates ERR33-C. Detect and handle standard library errors. There are only two condidtions in my code, cond1 and cond2. View - a subset of CWE entries that provides a way of examining CWE content. This is not a perfect solution, since 100% accuracy and coverage are not feasible. NULL can't point to data. I say "theoretical" because I have not successfully produced strings of this length in testing. Generating points along line with specifying the origin of point generation in QGIS. The NULL check is unnecessary because the pointer can't be NULL, so the NULL check should be removed. Where does the version of Hamapil that is different from the Gemara come from? specifies the length of the array for a function. NIST Workshop on Software Security Assurance Tools Techniques and Metrics. with solve of this bug problems have gone. At this point we define size as strlen(input_str) + 1. Avast and AVG Antivirus for Windows were susceptible to a NULL pointer dereference issue via RPC-interface. Use automated static analysis tools that target this type of weakness. Parabolic, suborbital and ballistic trajectories all follow elliptic paths. REVERSE_INULL False Positive "Dereference before NULL check" Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Suppressing a null dereference warning in static analysis coming from stub implementations in tests, Visual Studios giving me Dereferencing Null Pointer warning. NULL Pointer Dereference in mruby/mruby- vulnerability database . Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? 412-268-5800, 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 pointer. 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. 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). In Xcode 9 and later, you can use this check to detect the creation of null references and null pointer dereferences. /** Finally, there is the matter of the compliant solution. Chain: Use of an unimplemented network socket operation pointing to an uninitialized handler function (, Chain: race condition might allow resource to be released before operating on it, leading to NULL dereference, Chain: some unprivileged ioctls do not verify that a structure has been initialized before invocation, leading to NULL dereference, Chain: IP and UDP layers each track the same value with different mechanisms that can get out of sync, possibly resulting in a NULL dereference, Chain: uninitialized function pointers can be dereferenced allowing code execution, Chain: improper initialization of memory can lead to NULL dereference, Chain: game server can access player data structures before initialization has happened leading to NULL dereference, Chain: The return value of a function returning a pointer is not checked for success (, Chain: a message having an unknown message type may cause a reference to uninitialized memory resulting in a null pointer dereference (, Chain: unchecked return value can lead to NULL dereference. Why does this example of what compilers aren't allowed to do cause null pointer dereferencing using cmov? I'd guess null pointers are not valid, even though they point to 0 bytes. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. But passing 0 to memcpy() is not one of them. Loading. And in this case, there is no pointed-to data.