coverity null pointer dereference

Possible Null Pointer exception was found in a feature in which I'm the feature owner. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). uint64_t *var1 = NULL; this declares a uint64_t pointer (type uint64_t*). A deferred call's arguments are evaluated immediately, so the defer statement panics due to a nil response. I reordered that code example to do all the checks before allocations. availability of the system. Key here (explains table format and definitions), EXP34-C = Union( CWE-690, list) where list =. Why is this error being shown and is there a way to correct it? The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. specifies the length of the array for a function. In Xcode 9 and later, you can use this check to detect the creation of null references and null pointer dereferences. Created: Jan 26 2021 02:47:29 PM UTC Updated: Jan 26 2021 10:07:21 PM UTC . that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. Improper Check for Unusual or Exceptional Conditions, Unchecked Return Value to NULL Pointer Dereference, Memory Allocation with Excessive Size Value, Improperly Controlled Sequential Memory Allocation, OWASP Top Ten 2004 Category A9 - Denial of Service, CERT C Secure Coding Standard (2008) Chapter 4 - Expressions (EXP), CERT C Secure Coding Standard (2008) Chapter 9 - Memory Management (MEM), CERT C++ Secure Coding Section 03 - Expressions (EXP), CERT C++ Secure Coding Section 08 - Memory Management (MEM), SFP Secondary Cluster: Faulty Pointer Use, SEI CERT Oracle Secure Coding Standard for Java - Guidelines 02. But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. Will the ordering matter a bit more for the safe evaluation of involved expressions? See the "Null pointer checks may be optimized away more aggressively" section inhttps://gcc.gnu.org/gcc-4.9/porting_to.htmlas an example with one common implementation. CWE, CWSS, CWRAF, and the CWE logo are trademarks of The MITRE Corporation. The chunkdata pointer is later used as a destination argument in a call to memcpy(), resulting in user-defined data overwriting memory starting at address 0. The indicated severity is for this more severe case; on platforms where it is not possible to exploit a null pointer dereference to execute arbitrary code, the actual severity is low. It can never evaluate to true (unless Equals has been overridden to do something screwy). (C11, S7.24.2.1). Correct; a null pointer is not a valid pointer for the C library functions. What is the symbol (which looks similar to an equals sign) called? Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? It could cause e-mails stored with incorrect names. Coverity issue : Explicit Null dereferenced, How a top-ranked engineering school reimagined CS curriculum (Ep. <, [REF-1031] "Null pointer / Null dereferencing". 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). It also permits &x[y] to translate to x + y, but that is still UB if x is null because of ARR38-C. ISO C just has no similar wording for x->member. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I've posted an example for the sake of completion-. second, a de-reference of that variable. In this scenario, by the time, I come in 'cond2', I already have 'q' set. We should Zoom if you wish to talk more. What is it that I did not understand? 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. I see coverity defect with bold/italic code. Thank you for the description (comments).It Cleared my doubts. User without create permission can create a custom object from Managed package using Custom Rest API. :). 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. * @param vmToHost vm to host assignments Coverity Scan - Static Analysis And in this step. This has been there for decade, and was shipped in a real product. More information is available Please edit the custom filter or select a different filter. Why does Acts not mention the deaths of Peter and Paul? String URL = intent.getStringExtra("URLToOpen"); func HandleRequest(client http.Client, request *http.Request) (*http.Response, error) {. Even documented "we don't need to care, I think" issue can become an issue when one does not check the background implementation. Copy & paste errors might not often cause system crashes, but developer headaches. That interpretation of the standard is not supported universally. Improve INSERT-per-second performance of SQLite. Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. The choice could be made to use a language that is not susceptible to these issues. Why is this claimed dereferencing type-punned pointer warning compiler-specific? In this scenario, by the time, I come in 'cond2', I already have 'q' set. See C23 (n3096) s6.5.3.2p3: The unary & operator yields the address of its operand. Server allows remote attackers to cause a denial of service (crash) via malformed requests that trigger a null dereference. That exception could have rendered the entire feature non operational (And many log messages that Unused value and previous write overwriting found in the defect meant error in algorithm. Coverity found a case where a copy/paste action went wrong. So 'decoded' will always false. So the SIZE_MAX check was unnecessary. I've changed it to say null pointer instead of invalid pointer. This table shows the weaknesses and high level categories that are related to this weakness. ssh component for Go allows clients to cause a denial of service (nil pointer dereference) against SSH servers. What is it that I did not understand? Either the check against null is unnecessary, or there may be a null pointer dereference. 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. Carnegie Mellon University I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. Making statements based on opinion; back them up with references or personal experience. It depends on the specific details, but in general, taking the address of any valid memory is OK. <, [REF-1032] "Null Reference Creation and Null Pointer Dereference". Use automated static analysis tools that target this type of weakness. // 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. How a top-ranked engineering school reimagined CS curriculum (Ep. 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). I'll add that right now, but I feel it's pointless, since it will only clutter up the question. Find centralized, trusted content and collaborate around the technologies you use most. Overview. This bug ONLY surfaces when debugging or running the program with her verbosity. is undefined behavior (UB) if input does not actually point to a valid struct. What REALLY happens when you don't free after malloc before program termination? @HemantBhargava - you may know that, but the code you have shown us does not ensure that. Believing that dereferencing NULL shouldn't crash the system doesn't make it true. 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. 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. Find centralized, trusted content and collaborate around the technologies you use most. I added a comment to explain that SIZE_MAX is the limit of size_t. Could a subterranean river or aquifer generate enough continuous momentum to power a waterwheel for the purpose of producing electricity? The exact line that helped in your answer was this - "In this particular case, you're explicitly setting a_ptr to the address of a variable, so it can't possibly be NULL at that point. Connect and share knowledge within a single location that is structured and easy to search. This means one of two things: In this particular case, you're explicitly setting a_ptr to the address of a variable, so it can't possibly be NULL at that point. If the operand has type "type", the result has type "pointer to type". Dates. The HandleRequest function is intended to perform a request and use a defer to close the connection whenever the function returns. It would have been terrible to A simple decrement that wraps around causing an array overflow on lsm->lsm_oinfo[i[. Where does the version of Hamapil that is different from the Gemara come from? Can this be fixed if I reassign the *var1 to NULL again ?? 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. It modifies the pointed-to data. (I think you cover that in a different rule.) 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. More specific than a Base weakness. "Signpost" puzzle from Tatham's collection. 4500 Fifth Avenue Should I re-do this cinched PEX connection? Setting an incorrect jump target leads to a certain crash if the code is exercised. 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]. Alternate Terms Relationships Is there any known 80-bit collision attack? * Select VMs from the broken affinity group that are running on the same host. <, [REF-1033] "NULL Pointer Dereference [CWE-476]". Finding the distance from a corner of a cube to the midpoint of an edge. Explicitly initialize all your variables and other data stores, either during declaration or just before the first usage. of making the mruby interpreter crash, thus affecting the. Hence the error. 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. *var1 = 0; this dereferences the pointer, i.e. race condition causes a table to be corrupted if a timer activates while it is being modified, leading to resultant NULL dereference; also involves locking. Adding EV Charger (100A) in secondary panel (100A) fed off main (200A), Are these quarters notes or just eighth notes? At one point later, I get another warning: It seems like the line a_ptr->ptr = NULL is deemed incorrect/dangerous. I would also guess that pointers that point to the one-past-the-end of an array are also invalid. */. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. I have the following section of code, which gives explicit null dereferenced. Parabolic, suborbital and ballistic trajectories all follow elliptic paths. Apple. The platform is listed along with how frequently the given weakness appears for that instance. This is not a perfect solution, since 100% accuracy and coverage are not feasible. Chains can involve more than two weaknesses, and in some cases, they might have a tree-like structure. What should I follow, if two altimeters show different altitudes? The standard will simply copy 0 byteswhich is essentially a no-op. 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. Thanks for the reference to Julia Lawall's response to your question. 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! <, [REF-18] Secure Software, Inc.. "The CLASP Application Security Process". The sk pointer is initialized to tun->sk before checking if tun is a null pointer. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results. Would such an aspect be influenced in any ways if the address of operator would be applied around similar expressions? Possible Null Pointer exception was found in a feature in which I'm the feature owner. I would never have thought of looking at this piece of code if coverity hadn't found it. Each call of the impacted function may consumes many bytes (it's a file path). There are only two condidtions in my code, cond1 and cond2. New feature implementation got stuck for days because old code had obscure implementation which caused debuging nightmare. First if executes for cond1 and else executes for cond2.. Only one of them could be true at a time. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Game allows remote attackers to cause a denial of service (server crash) via a missing argument, which triggers a null pointer dereference. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. I'd really love to know why I'm being downvoted. If you don't set it again before the above if statement, that means that the NULL check is unnecessary and should be removed. int changed to size_t and if size_t parameter's is zero, allocate one word. this patch have merged in upstream master branch. .. 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. Best to cite C11 s7.24.2.1 here: The memcpy function copies n characters from the object pointed to by s2 into the object pointed to by s1. How come an array's address is equal to its value in C? Pointer members in structs are not checked. These types of problems usually lead to insidious correctness errors since exceptions are caught at a higher level. 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's not them. I have simplified it below (with the first warning)-, The code goes on to do several operations with a_ptr. 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.

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