Date: Mon, 8 Jan 2018 09:13:46 -0700 From: Warner Losh <imp@bsdimp.com> To: Pedro Giffuni <pfg@freebsd.org> Cc: Ed Schouten <ed@nuxi.nl>, Andrew Turner <andrew@fubar.geek.nz>, Ed Schouten <ed@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r327684 - in head/sys/compat: cloudabi32 cloudabi64 Message-ID: <CANCZdfq6DZ7_VaQALqrpqydsjJcyZOyV9uWEcTNQWJ_sR2T-cA@mail.gmail.com> In-Reply-To: <0a6ad324-46f2-9270-5abd-dbc3e734cc8b@FreeBSD.org> References: <201801072238.w07McjLP099234@repo.freebsd.org> <8D8CA434-2A87-44D9-AC27-5166802FBBC2@fubar.geek.nz> <CABh_MKm4HW2nJ=402oiELgWDo=Q7h15kjOU1p6F2BPOchjZCiw@mail.gmail.com> <0a6ad324-46f2-9270-5abd-dbc3e734cc8b@FreeBSD.org>
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On Jan 8, 2018 8:37 AM, "Pedro Giffuni" <pfg@freebsd.org> wrote: On 01/08/18 10:13, Ed Schouten wrote: > Hi Andrew, > > 2018-01-08 8:37 GMT+01:00 Andrew Turner <andrew@fubar.geek.nz>: > >> Won=E2=80=99t this lead to a NULL pointer dereference on overflow? mallo= carray >> can return NULL even with M_WAITOK. >> > Yes, it will, but an overflow shouldn't happen in the first place. > ri_data_len is compared with UIO_MAXIOV a few lines above. Even if an > overflow would happen, this would cause a kernel panic due to a NULL > pointer dereference later on, which is likely easier to debug than > some piece of code that overruns a buffer. > > In this case, mallocarray() is preferred, because it makes it more > obvious that we're allocating a buffer that is accessed as an array, > as opposed to single structure. > > OK... The behavior of mallocarray() somewhat inconsistent with malloc(9), realloc(9) and reallocf(9) but this is clearly documented., so we just assume the developer knows what he/she is doing :). This is one reason it didn't go in before... the error semantics suck... we re are a poor match for existing code. Warner
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