[Bug c++/19351] operator new[] can return heap blocks which are too small
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351 Jonathan Wakely redi at gcc dot gnu.org changed: What|Removed |Added CC||redi at gcc dot gnu.org --- Comment #23 from Jonathan Wakely redi at gcc dot gnu.org 2011-05-24 12:31:34 UTC --- Florian, your patch seems to have gone unreviewed, could you ping it? GCC is getting (fairly) criticised on the LLVM blog about this ;)
[Bug c++/19351] operator new[] can return heap blocks which are too small
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351 --- Comment #24 from Florian Weimer fw at gcc dot gnu.org 2011-05-24 19:54:47 UTC --- (In reply to comment #23) Florian, your patch seems to have gone unreviewed, could you ping it? Jason reviewed it and Ian, too (off-list). I haven't yet gotten around to incorporating their feedback. I'm also not sure if I'm qualified to tackle the optimization requests.
[Bug c++/19351] operator new[] can return heap blocks which are too small
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351 Florian Weimer fw at gcc dot gnu.org changed: What|Removed |Added CC||fw at gcc dot gnu.org --- Comment #22 from Florian Weimer fw at gcc dot gnu.org 2011-01-22 20:15:08 UTC --- New patch posted: http://gcc.gnu.org/ml/gcc-patches/2011-01/msg01593.html
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #21 from fw at gcc dot gnu dot org 2010-05-23 11:04 --- It turns out that the C++ committee did address this in C++0X, after rejected a previous DR. See section 18.6.2.2 in N3090. This seems to require an ABI change because the size calculation can no longer happen at the call site without much code bloat. See http://gcc.gnu.org/ml/gcc/2010-05/msg00437.html. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
-- fw at gcc dot gnu dot org changed: What|Removed |Added AssignedTo|fw at deneb dot enyo dot de |unassigned at gcc dot gnu ||dot org Status|ASSIGNED|NEW http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #19 from manu at gcc dot gnu dot org 2010-03-25 16:57 --- (In reply to comment #18) Perhaps someone could turn this into a landable patch https://bugzilla.mozilla.org/attachment.cgi?id=352646action=edit This seemed to fix the problem for us You just need a testcase, bootstrap and regression testing. -- manu at gcc dot gnu dot org changed: What|Removed |Added Keywords||patch http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #20 from fw at gcc dot gnu dot org 2010-03-25 17:13 --- (In reply to comment #19) You just need a testcase, bootstrap and regression testing. Test case (and a different patch) is here: http://gcc.gnu.org/ml/gcc-patches/2010-02/msg00275.html -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #18 from tglek at mozilla dot com 2010-03-22 18:40 --- Perhaps someone could turn this into a landable patch https://bugzilla.mozilla.org/attachment.cgi?id=352646action=edit This seemed to fix the problem for us -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
-- fw at gcc dot gnu dot org changed: What|Removed |Added AssignedTo|unassigned at gcc dot gnu |fw at deneb dot enyo dot de |dot org | Status|NEW |ASSIGNED http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #17 from mrs at apple dot com 2008-12-09 23:24 --- I agree, Apple would like this as well... radr://5739832 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #13 from pinskia at gcc dot gnu dot org 2008-04-01 20:46 --- *** Bug 35790 has been marked as a duplicate of this bug. *** -- pinskia at gcc dot gnu dot org changed: What|Removed |Added CC||felix-gcc at fefe dot de http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #14 from pinskia at gcc dot gnu dot org 2008-04-01 20:47 --- Also note unsigned types don't overflow, they wrap. So as far as I can tell, C++ defines this as being returning too small of a size. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #15 from felix-gcc at fefe dot de 2008-04-01 21:24 --- I think we can all agree it does not matter what we call this problem. Real world programs have security problems because of this. -fstack-protector carries a much larger run-time cost and gcc still offers it, and there is even less grounds to argue by any C or C++ standard that it's not the programmer's fault. gcc still offers it. As mentioned in the other bug, Microsoft Visual C++ already does this check. They do it like this. After the multiplication they check of the overflow flag is set, which on x86 indicates the result does not fit in the lower 32 bits. If so, instead of the truncated value it passes (size_t)-1 the operator new, which causes that operator new to fail (in the default case at least, a user may define its own operator new and that one might still return something). My favorite solution would be for the code to fail immediately. Throw an exception or return NULL, depending on which operator new the program called. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #16 from rguenth at gcc dot gnu dot org 2008-04-01 21:51 --- I agree. Patches welcome. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #10 from mmitchel at gcc dot gnu dot org 2007-03-23 15:00 --- What does the C standard say about calloc? That's a similar case; the multiplication is in calloc. Does it have to report an error? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #11 from schwab at suse dot de 2007-03-23 15:09 --- The calloc function allocates space for an array of nmemb objects, each of whose size is size. There is no mentioning of overflow, but the allocated space must surely be big enough to hold the array, and calloc shall fail if it cannot fulfill the request. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #12 from fw at deneb dot enyo dot de 2007-03-23 15:23 --- Subject: Re: operator new[] can return heap blocks which are too small * mmitchel at gcc dot gnu dot org: What does the C standard say about calloc? That's a similar case; the multiplication is in calloc. Does it have to report an error? My interpretation is that it must return NULL. (This was fixed in GNU libc years ago.) -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #8 from geoffk at gcc dot gnu dot org 2006-09-27 23:51 --- Isn't this handled by -ftrapv? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
Re: [Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #8 from geoffk at gcc dot gnu dot org 2006-09-27 23:51 --- Isn't this handled by -ftrapv? No because sizeof is unsigned and -ftrapv only deals with signed types. -- Pinski
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Comment #9 from pinskia at physics dot uc dot edu 2006-09-27 23:56 --- Subject: Re: operator new[] can return heap blocks which are too small --- Comment #8 from geoffk at gcc dot gnu dot org 2006-09-27 23:51 --- Isn't this handled by -ftrapv? No because sizeof is unsigned and -ftrapv only deals with signed types. -- Pinski -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-09 22:25 --- This is undefined behavor. Really there is nothing we can do, just think about this again, the programmer should catch this when they read in the length. -- What|Removed |Added Severity|normal |enhancement Status|UNCONFIRMED |RESOLVED Resolution||WONTFIX http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Additional Comments From fw at deneb dot enyo dot de 2005-01-09 22:35 --- Why is this undefined behavior? Would you quote chapter and verse, please? GCC's behavior violates 5.3.4(10): A new-expression passes the amount of space requested to the allocation function as the first argument of type std::size_t. That argument shall be no less than the size of the object being created; [...] In this case, the passed value is 16, which is much smaller than the size of the array. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-09 22:45 --- But the C++ standard does not say anything about this case. -- What|Removed |Added Status|RESOLVED|UNCONFIRMED Resolution|WONTFIX | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-09 22:47 --- I would get a clearification from the standards comittee if I were you. multiplying a large unsigned number by 16 and getting an overflow is werid case but again, the developer should be checking the size for reality, if they don't it can cause other problems like a seg fault as malloc on linux does not return null when running out of memory. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Additional Comments From bangerth at dealii dot org 2005-01-09 22:48 --- I also wonder what the semantics are that you are expecting? I mean, you try to allocate an array that is so large that you can't address the individual bytes using a size_t, in other words one that is larger than the address space the OS provides to your program. That clearly doesn't make any sense. That being said, I understand that the behavior of this is security relevant and that any attempt to allocate more memory than is available will necessarily have to fail. Thus, our present implementation isn't standards conforming, since it returns a reasonable pointer even in the case that the allocation should have failed. I would therefore agree that this is a problem, and given that memory allocation is an expensive operation, one overflow check isn't really time critical. Unfortunately, the situation is not restricted to libstdc++'s implementation of operator new[], since that operator only gets the total size of the memory to be allocation, not the size per element and the number of elements. Therefore, by the time we get into the implementation of this operator, it is already too late. In other words, the overflow check has to happen in compiler-generated code, not in the libstdc++ implementation. I would support the introduction of such code, if necessary guarded by some flag, or unconditionally, as a matter of quality of implemetation. W. -- What|Removed |Added Status|UNCONFIRMED |NEW Ever Confirmed||1 Last reconfirmed|-00-00 00:00:00 |2005-01-09 22:48:34 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Additional Comments From fw at deneb dot enyo dot de 2005-01-09 23:07 --- There's no multiplication in the source code. The multiplication is an implementation detail. You can hardly use it to justify the semantics of the operation. I would expect that std::bad_alloc is thrown. But I agree that the C++ standard isn't very clear in this area. The implementation must ensure that the postcondition in 5.3.4(10) holds, but the standard doesn't provide a means to signal failure. I'm going to post a note to comp.std.c++ on this matter, but hopefully this will be fixed in GCC as a quality of implementation issue. The necessary overflow check is should be very cheap because the multiplication is always by a constant. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
[Bug c++/19351] operator new[] can return heap blocks which are too small
--- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-09 23:11 --- (In reply to comment #6) There's no multiplication in the source code. The multiplication is an implementation detail. You can hardly use it to justify the semantics of the operation. Actually the multiplication is not an implementation detail. The standard says what opator new[] should be passed, just the multiplication is included. sizeof(int[i]) (well if it was valid C++, it is valid C99) is defined as a multiplication so it is not an implemenation detail. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
