If code1 and code2 may both be true, though, then you do have a substantial bug here. 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. There are only two condidtions in my code, cond1 and cond2. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results. *var1 = 0; this dereferences the pointer, i.e. 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). Where does the version of Hamapil that is different from the Gemara come from? Customer's opinion is that it is always a good practice to check a pointer for a NULL Value before freeing it. EXP34-C. Do not dereference null pointers - Confluence <<< 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. However, I must add a few qualifications: First of all, there is the question of whether this is for C or for C++. 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. But passing 0 to memcpy() is not one of them. I'm sorry if I have misunderstood the intent in your question. It modifies the pointed-to data. Software Engineering Institute is undefined behavior (UB) if input does not actually point to a valid struct. accesses memory stored at its address. Coverity - forward null dereference #1747 - Github Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. There are other problems with this code, as is noted in the rule. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. Assign an array of Swift strings to a C structure variable taking a char ** value. It modifies the pointed-to data. I got the impression that 31 source files of Linux modules will need further adjustments. 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. This warning thrown by Coverity if you dereference a pointer and then later on do a NULL check on it. Category - a CWE entry that contains a set of other entries that share a common characteristic. New feature implementation got stuck for days because old code had obscure implementation which caused debuging nightmare. Extended Description NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. Iflengthhas the value1, the addition yields 0, and png_malloc() subsequently returns a null pointer, which is assigned to chunkdata. Why are players required to record the moves in World Championship Classical games? Adding EV Charger (100A) in secondary panel (100A) fed off main (200A), Are these quarters notes or just eighth notes? Coverity scan helps our developers finding issues like these. Find centralized, trusted content and collaborate around the technologies you use most. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Buffer overflow and possibly corrupting the module database. 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. Base - a weakness Improve INSERT-per-second performance of SQLite. Thank you for clarifying your assertion until I understood it properly. 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. Various developers and code reviewers are struggling also with evolution of the specifications for such programming languages. The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. Did the drapes in old theatres actually say "ASBESTOS" on them? This compliant solution ensures that the pointer returned by png_malloc() is not null. :). 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). I'd guess WG14 has considered these questions, but I haven't until now :). Network monitor allows remote attackers to cause a denial of service (crash) via a malformed Q.931, which triggers a null dereference. Developer Description. * @return a list of vms which are candidates for migration When this happens, CWE refers to X as "primary" to Y, and Y is "resultant" from X. User without create permission can create a custom object from Managed package using Custom Rest API. assert(!invalid(p)); // or whatever, bool invalid(const void *p) { It is kind of funny, though. It would be tricky, and they would want WG14 (C working group) to at least bless this change, and more likely, make the analogous change to the C standard. Standing by. Copyright 20062023, The MITRE Corporation. Can corresponding author withdraw a paper after it has accepted without permission/acceptance of first author. Why does the second compliant example permit using possibly-null pointers? 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). The description The sk pointer is initialized to tun->sk before checking if tun is a null pointer. is provided for a non-compliant code example.Thus it seems that the arrow operator (member access through pointer) is usually treated also as a dereference operation. OS allows remote attackers to cause a denial of service (crash from null dereference) or execute arbitrary code via a crafted request during authentication protocol selection. 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. 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. . It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); 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. And in this case, there is no pointed-to data. (I think you cover that in a different rule.) Thank you for the description (comments).It Cleared my doubts. Dates. Thanks for contributing an answer to Stack Overflow! What is this brick with a round back and a stud on the side used for? The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. c - Coverity issue : Explicit Null dereferenced - Stack Overflow The two languages try to maximize compatibility, . In this scenario, by the time, I come in 'cond2', I already have 'q' set. Category. Why don't we use the 7805 for car phone chargers? REVERSE_INULL False Positive "Dereference before NULL check" 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. In this scenario, by the time, I come in 'cond2', I already have 'q' set. mruby is vulnerable to NULL Pointer. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). Search for vulnerabilities resulting from the violation of this rule on the CERT website. 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. NIST Workshop on Software Security Assurance Tools Techniques and Metrics. This code also violates ERR33-C. Detect and handle standard library errors. 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. which bolsters my assertion that x->member dereferences x (or at least an offset of x). *var1 = 0; this dereferences the pointer, i.e. Isn't easier just to check valid range of length? ), [REF-6] Katrina Tsipenyuk, Brian Chess CPE Name Name Version; mruby: 3.1.0: Products. Pittsburgh, PA 15213-2612 I believe that dereferencing NULL should not crash the system, should not allow a write to a NULL pointer area, but should always set errno, If I am a hacker, could I trap a null failure that would force a memory dump. mruby is vulnerable to NULL Pointer Dereference Affected Software. 4500 Fifth Avenue . Making statements based on opinion; back them up with references or personal experience. For users who are concerned with the practical application and details about the nature of a weakness and how to prevent it from happening. ), NPD.CHECK.CALL.MIGHTNPD.CHECK.CALL.MUSTNPD.CHECK.MIGHTNPD.CHECK.MUSTNPD.CONST.CALLNPD.CONST.DEREFNPD.FUNC.CALL.MIGHTNPD.FUNC.CALL.MUSTNPD.FUNC.MIGHTNPD.FUNC.MUSTNPD.GEN.CALL.MIGHTNPD.GEN.CALL.MUSTNPD.GEN.MIGHTNPD.GEN.MUSTRNPD.CALLRNPD.DEREF, 45 D, 123 D, 128 D, 129 D, 130 D, 131 D, 652 S, Checks for use of null pointers (rule partially covered). Canadian of Polish descent travel to Poland with Canadian passport. This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. Either the check against null is unnecessary, or there may be a null pointer dereference. However there is no portable way to verify that the pointer is valid, other than checking for null. If the operand has type "type", the result has type "pointer to type". rev2023.5.1.43405. Coverity Scan - Static Analysis Unexpected behavior can be pain to hunt down when one of these is involved. Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. Making statements based on opinion; back them up with references or personal experience. So we have to check all the arguments before performing any actions. This error detected by CoverityScan detected a case where the driver would never run at the maximum CPI clock speed. It would cause game actors to teleport to the wrong coordinates. very useful to find this very horrible bug in this case, we're using a pointer to memory which is not guaranteed to be zero, and potentially corrupting the malloc arena in the process. Why the obscure but specific description of Jane Doe II in the original complaint for Westenbroek v. Kappa Kappa Gamma Fraternity? NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. SSL software allows remote attackers to cause a denial of service (crash) via a crafted SSL/TLS handshake that triggers a null dereference. repository mruby/mruby prior to 3.2. 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. . Agreed. Why does the narrative change back and forth between "Isabella" and "Mrs. John Knightley" to refer to Emma's sister? The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase. The question is concise, clear, to-the-point and logical. ', referring to the nuclear power plant in Ignalina, mean? Since SIZE_MAX represents the largest possible object, the largest possible string would then be SIZE_MAX-1 characters long (excluding '\0'). Network monitor allows remote attackers to cause a denial of service (crash) via a malformed RADIUS packet that triggers a null dereference. Otherwise, the result is a pointer to the object or function designated by its operand. I reordered that code example to do all the checks before allocations. Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. 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. Apple. ", Getting warning - Dereferencing before possibly being null in C code, How a top-ranked engineering school reimagined CS curriculum (Ep. Note that this code is also vulnerable to a buffer overflow (CWE-119). is undefined behavior (UB) if input does not actually point to a valid struct. But no where in that particular idiom would a NULL pointer necessarily be deferenced. To learn more, see our tips on writing great answers. 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. COVERITY checker description | The STAR experiment Why does the narrative change back and forth between "Isabella" and "Mrs. John Knightley" to refer to Emma's sister? The null pointer check for writing or dereferencing should be a compiler flag or library setting. 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(). The sk pointer is initialized to tun->sk before checking if tun is a null pointer. 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 an invalid value has been assigned to the pointer, the behavior of the unary * operator is undefined.115). and Gary McGraw. NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. Connect and share knowledge within a single location that is structured and easy to search. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The platform does add offsetof( struct_type, member) to input and dereferences that. // Find a VM that is breaking the affinityGroup and can be theoretically migrated, findVmViolatingPositiveAg(affinityGroup, vmToHost), org.ovirt.engine.core.dao.VmDaoImpl.getVmsByIds, Positive affinity group violation detected, Negative affinity group violation detected, // Test whether any migration is possible, this uses current AffinityGroup settings. Separate it into a different function that you can call. 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. Not the answer you're looking for? This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. 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. Could I capture, and I would be able to glean much security information from the dump? * Select VMs from the broken affinity group that are running on the same host. 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. Copy & paste errors might not often cause system crashes, but developer headaches. 33615. Good question! that is linked to a certain type of product, typically involving a specific language or technology. Why don't we use the 7805 for car phone chargers? What does 'They're at four. How a top-ranked engineering school reimagined CS curriculum (Ep. In your case you are not doing it,so you have a segmentation fault(or crash) . 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! If you don't set it again before the above if statement, that means that the NULL check is unnecessary and should be removed. More specific than a Base weakness. I say "theoretical" because I have not successfully produced strings of this length in testing. Asking for help, clarification, or responding to other answers. This is in the key management code which converts passwords. Use automated static analysis tools that target this type of weakness. Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). This does not have any impact, because it is just an assert. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. Solution 1, it looks like, today's solution tomorrow's problem. What were the most popular text editors for MS-DOS in the 1980s? One situation this can happen is when the pointer has been checked against NULL and is dereferenced later. 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. 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. (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). 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. I see coverity defect with bold/italic code. The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. 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. One of the Coccinelle software maintainers expressed opposite development views today. Possible Null Pointer exception was found in a feature in which I'm the feature owner. Coverity Collector User Votes: 0 Vote for this issue Watchers: 1 Start watching this issue. 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. This check identifies such situation by checking all possible paths where such NULL dereferences can occur. Making statements based on opinion; back them up with references or personal experience. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. Finding the distance from a corner of a cube to the midpoint of an edge. Coverity Scan - Static Analysis By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. I believe in this case, either expression would work. /** 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. He also rips off an arm to use as a sword, Canadian of Polish descent travel to Poland with Canadian passport, assertions usually only apply at debug-time (as I was recently reminded with a runtime crash in a release build that made no sense after all, I have assertion safety everywhere, right?). See C23 (n3096) s6.5.3.2p3: The unary & operator yields the address of its operand. The issue is: memcpy() and friends do not explicitly state that a null pointer is a valid pointer value, even if the number of bytes to copy is 0. If the compiler finds a pointer dereference, it treats that pointer as nonnull. c++ - Coverity -- Explicit null dereference - Stack Overflow Right? If you don't set it again before the above if statement, that means that the NULL check is unnecessary and should be removed. "Signpost" puzzle from Tatham's collection. 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. 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 REALLY happens when you don't free after malloc before program termination? Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? This code will definitely crash due to a null pointer dereference in certain cases. Coverity Scan - Static Analysis Would you become interested in a related clarification approach for a discussion topic like . 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. This pointer was the resaon of a memory leak Realy nice catch by Coverity. I added a comment to explain that SIZE_MAX is the limit of size_t. VM {} is NOT a viable candidate for solving affinity group violation situation. If you want to change the value of your pointer, just do var1 = 0; 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." What is it that I did not understand? Made code more compliant with other rules. What's the rationale for null terminated strings? Variant - a weakness How to force Unity Editor/TestRunner to run at full speed when in background? 2005. Simple deform modifier is deforming my object, xcolor: How to get the complementary color. This table specifies different individual consequences associated with the weakness. 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 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.
G Shine Blood Handshake, Is He A Workaholic Or Not Interested, Articles C