Date: Sat, 10 Jan 2004 14:31:42 -0800 (PST) From: Don Lewis <truckman@FreeBSD.org> To: nectar@FreeBSD.org Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern uipc_syscalls.c Message-ID: <200401102231.i0AMVg7E028954@gw.catspoiler.org> In-Reply-To: <20040110152347.GD80448@madman.celabo.org>
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On 10 Jan, Jacques A. Vidrine wrote: > On Sat, Jan 10, 2004 at 12:28:54AM -0800, Don Lewis wrote: >> truckman 2004/01/10 00:28:54 PST >> >> FreeBSD src repository >> >> Modified files: >> sys/kern uipc_syscalls.c >> Log: >> Add a somewhat redundant check on the len arguement to getsockaddr() to >> avoid relying on the minimum memory allocation size to avoid problems. >> The check is somewhat redundant because the consumers of the returned >> structure will check that sa_len is a protocol-specific larger size. >> >> Submitted by: Matthew Dillon <dillon@apollo.backplane.com> >> Reviewed by: nectar >> MFC after: 30 days > > But the check *is not* redundant. The consumers cannot safely check > sa_len if the allocation were to be less than `offsetof(struct > sa_sockaddr, data[0])'--- which it never is, by chance, due to the > minimum memory allocation size, as you noted. But we shall all feel > better that this is made explicit. FWIW, I think the check should > have been for `sizeof(*sa)' technically, but what has been committed > is safe, too, I believe. The only reason it is redundant instead of manditory is because of the minimum allocation allocation happens to be large enough for getsockaddr() to write to sa_len. If it is safe for getsockaddr() to write to sa_len, then it is safe for the consumers to read sa_len. BTW, I think a better solution is for getsockaddr() to call an address family specific length checker before returning, and to remove the sa_len check from all the consumers. With the commit I did to the tcp code after this commit, sa_len is checked three times for the bind() and connect() syscalls. I wasn't feeling that ambitious, though. It looks like the AF_UNIX implementation allows the length to be shorter than sizeof(*sa). It appears that you don't have to pass in the full 104 character sun_path.
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