Either the check against null is unnecessary, or there may be a null pointer dereference. Believing that dereferencing NULL shouldn't crash the system doesn't make it true. Network monitor allows remote attackers to cause a denial of service (crash) via a malformed Q.931, which triggers a null dereference. I'm getting a warning while doing a Static Analysis (SA) on my code. Not the answer you're looking for? As a result, the optimizer may remove null . A pointer should be made to point to some valid memory location before writing something to it. Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? In this case, the difference is the assumption thatmalloc() always returns non-nullfor the second NCCE, whereas the first NCCE has themalloc() abstracted away. Did the drapes in old theatres actually say "ASBESTOS" on them? In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore. 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(). This Android application has registered to handle a URL when sent an intent: The application assumes the URL will always be included in the intent. Not the answer you're looking for? Can corresponding author withdraw a paper after it has accepted without permission/acceptance of first author. Similarly, if the operand is the result of a [] operator, neither the & operator nor the unary * that is implied by the [] is evaluated and the result is as if the & operator were removed and the [] operator were changed to a + operator. What is the symbol (which looks similar to an equals sign) called? * @param affinityGroup broken affinity rule The final NCCE is actually more insidious than it seems at first. Where does the version of Hamapil that is different from the Gemara come from? It does not give the pointer a new value. Category. This is the intention for the referenced small script of the semantic patch language. accesses memory stored at its address. 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. Right? 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. And in this case, there is no pointed-to data. Check the results of all functions that return a value and verify that the value is non-null before acting upon it. See "Clever Attack Exploits Fully-Patched Linux Kernel" [Goodin 2009] for an example of a code execution exploit that resulted from a null pointer dereference. Making statements based on opinion; back them up with references or personal experience. It should be an ingrained practice. 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. This rule applies to all null pointers, regardless of which function returned them. Then we hit memcpy with length 0. The libpng library implements its own wrapper to malloc() that returns a null pointer on error or on being passed a 0-byte-length argument. 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. In this scenario, by the time, I come in 'cond2', I already have 'q' set. 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. 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. The issue was fixed with Avast and AVG Antivirus version 22.11 Publish Date : 2023-04-19 Last Update Date : 2023-04-19 Collapse All Expand All Select Select&Copy Scroll To Vendor . If code1 and code2 may both be true, though, then you do have a substantial bug here. Canadian of Polish descent travel to Poland with Canadian passport. 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). When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. 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. The code is dead and will be never processed because 'decoded' outside the scope and redefined in local. This table shows the weaknesses and high level categories that are related to this weakness. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? 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). Why don't we use the 7805 for car phone chargers? Coverity - forward null dereference #1747 - Github Buffer overflow difficult to find by reading the code that would result a crash if path is too long. At one point later, I get another warning: It seems like the line a_ptr->ptr = NULL is deemed incorrect/dangerous. <<< 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. C/C++ Dereference error: Dereference before null check, Solving C warning - dereferencing a null pointer. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) Setting an incorrect jump target leads to a certain crash if the code is exercised. CalebFenton/simplify. 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. valgrind wasnt that usefull because of its slowness. Making statements based on opinion; back them up with references or personal experience. availability of the system. The NULL check is unnecessary because the pointer can't be NULL, so the NULL check should be removed. It also uses the unsigned type size_t to pass the length parameter, ensuring that negative values are not passed to func(). 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. Adding EV Charger (100A) in secondary panel (100A) fed off main (200A), Are these quarters notes or just eighth notes? Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 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. I note with interest, that ISO C does permit &*x when x is null. Dates. 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?). COVERITY checker description | The STAR experiment However, I must add a few qualifications: First of all, there is the question of whether this is for C or for C++. I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. 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. So before writing anything to some memory location memory has to allocated to the pointer. Copyright 20062023, The MITRE Corporation. * @return a list of vms which are candidates for migration These types of problems usually lead to insidious correctness errors since exceptions are caught at a higher level. 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! An extremely nice thing which was discovered only by Coverity. Connect and share knowledge within a single location that is structured and easy to search. Chain - a Compound Element that is a sequence of two or more separate weaknesses that can be closely linked together within software. Apple. */. Not the answer you're looking for? In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. mruby is vulnerable to NULL Pointer Dereference Affected Software. When the URL is not present, the call to getStringExtra() will return null, thus causing a null pointer exception when length() is called. Does &((struct name *)NULL -> b) cause undefined behaviour in C11? 33615. This is a matter of style, and also following code walkthrough. It is pretty easy to miss such things when adding a new feature. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. I see coverity defect with bold/italic code. The choice could be made to use a language that is not susceptible to these issues. Key here (explains table format and definitions), EXP34-C = Union( CWE-690, list) where list =. void host_lookup(char *user_supplied_addr){, if("com.example.URLHandler.openURL".equals(intent.getAction())) {. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation. Simple and excellent job. Without coverity i probably would not have found this copy&paste error. Find centralized, trusted content and collaborate around the technologies you use most. We've been getting report on the random crashes, and here it is, the swapped check for index and actual indexed array value. 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. The two languages try to maximize compatibility, and occasionally succeed. Coverity Collector User Votes: 0 Vote for this issue Watchers: 1 Start watching this issue. DATABASE RESOURCES PRICING ABOUT US. 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 looks like a logic bug, which can cause a memory leaking. But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. To learn more, see our tips on writing great answers. <, [REF-1032] "Null Reference Creation and Null Pointer Dereference". can have the value zero on a call to that function. That's true. Coverity scan helps our developers finding issues like these. In Coverity, FORWARD_NULL reports defects when there are enough evidences to be sure the null access will (can) happen. Base - a weakness Description. 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. . Good question! .. 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. pointers - Getting warning - Dereferencing before possibly being null it may still not be enough to satisfy Coverity. Hence the error. My guess is it is telling you "you are doing the NULL check now, but you have already dereferenced it before. In particular, this paragraph enables & to cancel out * (eg &*x == x) and [] (eg &x[5] == x + 5), but not ->. }. To fix the bug in the code and also make Coverity happy, as suggested by derHugo in a comment, change the RemoveAll line to something like this: Thanks for contributing an answer to Stack Overflow! NULL Pointer Dereference in mrb_vm_exec with super in It evaluates to true if a_ptr is not NULL. 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. And in this case, there is no pointed-to data. First if executes for cond1 and else executes for cond2.. Only one of them could be true at a time. Explicitly initialize all your variables and other data stores, either during declaration or just before the first usage. The question is concise, clear, to-the-point and logical. It also reinforces the notion to the reader that any time you see arithmetic in an allocation expression, you need to think about corner-cases. 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). 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. Did the drapes in old theatres actually say "ASBESTOS" on them? I'm sorry if I have misunderstood the intent in your question. This listing shows possible areas for which the given weakness could appear. large number of packets leads to NULL dereference, packet with invalid error status value triggers NULL dereference, Chain: race condition for an argument value, possibly resulting in NULL dereference. but we still consider it a violation of this rule for practicality, although to be anal, it is instead a violation of ARR30-C. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Many platforms can support testing for those also. <. Phew, we're agreed here. This check identifies such situation by checking all possible paths where such NULL dereferences can occur. Asking for help, clarification, or responding to other answers. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Variant - a weakness It can never evaluate to true (unless Equals has been overridden to do something screwy). Which language's style guidelines should be used when writing code that is supposed to be called from another language? That exception could have rendered the entire feature non operational (And many log messages that the user wouldn't understand). Would you like to help any further according to different understanding and expectations for affected implementation details. A deferred call's arguments are evaluated immediately, so the defer statement panics due to a nil response. Identify error conditions that are not likely to occur during normal usage and trigger them. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The above check can't hurt, as I guess you could have a system with a 32-bit size_t that had a ton of memory and had some crazy banking/selector scheme with pointers. Asking for help, clarification, or responding to other answers. Correct; a null pointer is not a valid pointer for the C library functions. Coverity complains below message: I do not understand why coverity complains here. NIST Workshop on Software Security Assurance Tools Techniques and Metrics. Unfortunately, your link also points to code that violates this rule, and is thus undefined behavior. NULL can't point to data. But passing 0 to memcpy() is not one of them. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Thanks, David! I'll add that right now, but I feel it's pointless, since it will only clutter up the question. The added benefit of this is that you probably no longer require both p and q and so the entire function becomes far more lean. Identify all variables and data stores that receive information from external sources, and apply input validation to make sure that they are only initialized to expected values. User without create permission can create a custom object from Managed package using Custom Rest API. Thanks for this checker. Developer Description. 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 you don't set it again before the above if statement, that means that the NULL check is unnecessary and should be removed. The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. 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). Simple deform modifier is deforming my object, xcolor: How to get the complementary color. 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. Synopsys, Inc. | Policy Statement | Contact. 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. This compliant solution ensures that the pointer returned by png_malloc() is not null. 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. Allowing it to be removed. 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. Null reference creation and null pointer dereference Server allows remote attackers to cause a denial of service (crash) via malformed requests that trigger a null dereference. If the operand has type "type", the result has type "pointer to type". It could cause e-mails stored with incorrect names. <, [REF-1031] "Null pointer / Null dereferencing". Hence the error. Embedded hyperlinks in a thesis or research paper, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A). 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? * It seems that my understanding needs also to grow for such information. What were the most popular text editors for MS-DOS in the 1980s? Network monitor allows remote attackers to cause a denial of service (crash) or execute arbitrary code via malformed packets that cause a NULL pointer dereference. 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
Lincare Medical Supplies,
Barclays Won't Let Me Add New Payee,
Resident Cosmetic Surgery Clinic Near Me,
Dataframe' Object Has No Attribute Orderby Pyspark,
Neighbors Loud Pool Parties,
Articles C