coverity null pointer dereference

I note with interest, that ISO C does permit &*x when x is null. I'd guess null pointers are not valid, even though they point to 0 bytes. but we still consider it a violation of this rule for practicality, although to be anal, it is instead a violation of ARR30-C. Is there a generic term for these trajectories? The 4gig boundary will probably be important too with unsigned int in LP64, but since size_t will be 64-bit, there will have to be some truncation that compilers will be able to warn on. c++ - Coverity -- Explicit null dereference - Stack Overflow This bug ONLY surfaces when debugging or running the program with her verbosity. FORWARD_NULL: A program will normally crash when a NULL pointer is dereferenced. NULL Pointer Dereference in mrb_vm_exec with super in GitHub. Buffer overflow difficult to find by reading the code that would result a crash if path is too long. and Gary McGraw. Coverity Scan - Static Analysis NIST Workshop on Software Security Assurance Tools Techniques and Metrics. It's even called out explicitly in C17 7.24.1p2: Where an argument declared as size_t n specifies the length of the array for a function, n can have the value zero on a call to that function. * Off by one error: It is the third example. On many platforms, dereferencing a null pointer results inabnormal program termination, but this is not required by the standard. Separate it into a different function that you can call. 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. Carnegie Mellon University Although i'm only We haven't noticed an impact of the bug but the out of bounds access has been present since at least 2009 without anybody spotting it. CWE - CWE-476: NULL Pointer Dereference (4.11) - Mitre Corporation This pointer was the resaon of a memory leak Realy nice catch by Coverity. "Signpost" puzzle from Tatham's collection, Image of minimal degree representation of quasisimple group unique up to conjugacy. While not explicitly mentioning UB, I would infer that *NULL is UB since NULL is not a pointer to an object or function type. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? It is pretty easy to miss such things when adding a new feature. Network monitor allows remote attackers to cause a denial of service (crash) via a malformed RADIUS packet that triggers a null dereference. 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. Asking for help, clarification, or responding to other answers. 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. But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. Possibly Clang/LLVM may choose to always return a valid value for &NULL->member. Can this be fixed if I reassign the *var1 to NULL again. This one is pretty awesome. What is this brick with a round back and a stud on the side used for? In your case you are not doing it,so you have a segmentation fault(or crash) . Network monitor allows remote attackers to cause a denial of service (crash) via a malformed Q.931, which triggers a null dereference. Dereferencing a null pointer always results in undefined behavior and can cause crashes. This error detected by CoverityScan detected a case where the driver would never run at the maximum CPI clock speed. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact. The two languages try to maximize compatibility, and occasionally succeed. Overall, I disagree with her answer, and agree with the StackOverflow response (https://stackoverflow.com/questions/25725286/does-taking-address-of-member-variable-through-a-null-pointer-yield-undefined-be). Asking for help, clarification, or responding to other answers. Standing by. Chain - a Compound Element that is a sequence of two or more separate weaknesses that can be closely linked together within software. NULL can't point to data. If the compiler finds a pointer dereference, it treats that pointer as nonnull. In particular, this paragraph enables & to cancel out * (eg &*x == x) and [] (eg &x[5] == x + 5), but not ->. 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. Event var_deref_model: | Passing null pointer "master_uri_env" to "operator =", which dereferences it. Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). Coverity issue : Explicit Null dereferenced, How a top-ranked engineering school reimagined CS curriculum (Ep. An extremely nice thing which was discovered only by Coverity. If code1 and code2 may both be true, though, then you do have a substantial bug here. I suggest that this topic needs to include calloc() and realloc() Refer to Linux man pages online for more enlightenment about malloc(), and friends. It even looked as a false positive at first. Found logically dead code that would never have been accessed. {"serverDuration": 277, "requestCorrelationId": "e2a1d936a1543fbd"}, EXP34-C. Do not dereference null pointers, Clever Attack Exploits Fully-Patched Linux Kernel, ERR33-C. Detect and handle standard library errors, one compliant and one non-compliant example, CERT Oracle Secure Coding Standard for Java, EXP01-J. that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. with solve of this bug problems have gone. 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. unity3d - C# Coverity giving "Dereference before null check (REVERSE Coverity is giving you a warning because you are in fact doing a NULL check: Here, a_ptr is evaluated in a boolean context. Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. accesses memory stored at its address. Why does this example of what compilers aren't allowed to do cause null pointer dereferencing using cmov? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. This rule applies to all null pointers, regardless of which function returned them. Horizontal and vertical centering in xltabular. Otherwise, the result is a pointer to the object or function designated by its operand. 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). Game allows remote attackers to cause a denial of service (server crash) via a missing argument, which triggers a null pointer dereference. The two languages try to maximize compatibility, . 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. accesses memory stored at its address. DATABASE RESOURCES PRICING ABOUT US. Connect and share knowledge within a single location that is structured and easy to search. /** I say "theoretical" because I have not successfully produced strings of this length in testing. Thank you for clarifying your assertion until I understood it properly. Making statements based on opinion; back them up with references or personal experience. I've changed it to say null pointer instead of invalid pointer. Your assertion is not backed by the wording in the standard, nor by common implementer understanding. 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). int changed to size_t and if size_t parameter's is zero, allocate one word. Use of the Common Weakness Enumeration (CWE) and the associated references from this website are subject to the Terms of Use. specifies the length of the array for a function. Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. NULL Pointer Dereference in mruby/mruby- vulnerability database So the SIZE_MAX check was unnecessary. It is a corner case that would flash once in the blue moon - but with serious impact on the production availability. Setting an incorrect jump target leads to a certain crash if the code is exercised. 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?). 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. At one point later, I get another warning: It seems like the line a_ptr->ptr = NULL is deemed incorrect/dangerous. How to remove elements from a generic list while iterating over it? Category. Server allows remote attackers to cause a denial of service (crash) via malformed requests that trigger a null dereference. that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Solution 1, it looks like, today's solution tomorrow's problem. I find it interesting in this case how you think in another direction. No affinity group collision detected for cluster {}. String URL = intent.getStringExtra("URLToOpen"); func HandleRequest(client http.Client, request *http.Request) (*http.Response, error) {. . So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). 2021-12-15T00:00:00 Description. Extended Description NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. In Coverity, FORWARD_NULL reports defects when there are enough evidences to be sure the null access will (can) happen. And in this step. That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. 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(). 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.

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