Date: Sun, 11 Dec 2011 10:30:04 GMT From: Jaakko Heinonen <jh@FreeBSD.org> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/163076: It is not possible to read in chunks from linprocfs and procfs. Message-ID: <201112111030.pBBAU4fe032247@freefall.freebsd.org>
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The following reply was made to PR kern/163076; it has been noted by GNATS. From: Jaakko Heinonen <jh@FreeBSD.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: Petr Salinger <Petr.Salinger@seznam.cz>, bug-followup@FreeBSD.org, des@FreeBSD.org, mdf@FreeBSD.org Subject: Re: kern/163076: It is not possible to read in chunks from linprocfs and procfs. Date: Sun, 11 Dec 2011 12:26:08 +0200 On 2011-12-10, Poul-Henning Kamp wrote: > I agree with Dag-Erling that it is at least mistake to not have > separate sbuf(9) and sbuf(3) pages, possibly also a mistake that > they share the implementation. One problem is the different malloc() semantics. The kernel version uses M_WAITOK allocations while user space malloc(3) can fail. > Obviously sbuf_finish() should return the error status, and its > return value SHALL be checked by applications, before the contents > of the sbuf can be used. Only 21 of 133 calls I grepped through the FreeBSD source tree did check the return value. In practice SBUF_AUTOEXTEND buffers can't fail when the kernel version is used (due to M_WAITOK malloc). > The argument relating to this bug is about what sbuf_len() and > sbuf_data() should return for an error'ed sbuf. > > Given that the mandatory error-check of the sbuf_finish() call > should prevent these two functions from being called in the first > place, I'm tempted to say that their return values should be > documented as undefined, and implemented to cause the maxium amount > of havoc (ie: -1 and NULL). -- Jaakko
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