Date: Wed, 24 Aug 2022 17:36:01 GMT From: Brooks Davis <brooks@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: c46697b9cb97 - main - freebsd32_sendmsg: fix control message ABI Message-ID: <202208241736.27OHa1qW013299@gitrepo.freebsd.org>
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The branch main has been updated by brooks: URL: https://cgit.FreeBSD.org/src/commit/?id=c46697b9cb97a14f61ac0a58758aab081b9e48c5 commit c46697b9cb97a14f61ac0a58758aab081b9e48c5 Author: Brooks Davis <brooks@FreeBSD.org> AuthorDate: 2022-08-24 17:34:39 +0000 Commit: Brooks Davis <brooks@FreeBSD.org> CommitDate: 2022-08-24 17:34:39 +0000 freebsd32_sendmsg: fix control message ABI When a freebsd32 caller uses all or most allowed space for control messages (MCLBYTES == 2K) then the message may no longer fit when the messages are padded for 64-bit alignment. Historically we've just shrugged and said there is no ABI guarantee. We ran into this on CheriBSD where a capsicumized 64-bit nm would fail when called with more than 64 files. Fix this by not gratutiously capping size of mbuf data we'll allocate to MCLBYTES and let m_get2 allocate up to MJUMPAGESIZE (4K or larger). Instead of hard-coding a length check, let m_get2 do it and check for a NULL return. Reviewed by: markj, jhb, emaste Sponsored by: DARPA, AFRL Differential Revision: https://reviews.freebsd.org/D36322 --- sys/compat/freebsd32/freebsd32_misc.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/sys/compat/freebsd32/freebsd32_misc.c b/sys/compat/freebsd32/freebsd32_misc.c index d1c44a4f9952..b4c212ecd38d 100644 --- a/sys/compat/freebsd32/freebsd32_misc.c +++ b/sys/compat/freebsd32/freebsd32_misc.c @@ -1535,6 +1535,7 @@ freebsd32_copyin_control(struct mbuf **mp, caddr_t buf, u_int buflen) u_int msglen, outlen; int error; + /* Enforce the size limit of the native implementation. */ if (buflen > MCLBYTES) return (EINVAL); @@ -1570,20 +1571,20 @@ freebsd32_copyin_control(struct mbuf **mp, caddr_t buf, u_int buflen) outlen += CMSG_ALIGN(sizeof(*cm)) + CMSG_ALIGN(msglen - FREEBSD32_ALIGN(sizeof(*cm))); } - if (error == 0 && outlen > MCLBYTES) { - /* - * XXXMJ This implies that the upper limit on 32-bit aligned - * control messages is less than MCLBYTES, and so we are not - * perfectly compatible. However, there is no platform - * guarantee that mbuf clusters larger than MCLBYTES can be - * allocated. - */ - error = EINVAL; - } if (error != 0) goto out; + /* + * Allocate up to MJUMPAGESIZE space for the re-aligned and + * re-padded control messages. This allows a full MCLBYTES of + * 32-bit sized and aligned messages to fit and avoids an ABI + * mismatch with the native implementation. + */ m = m_get2(outlen, M_WAITOK, MT_CONTROL, 0); + if (m == NULL) { + error = EINVAL; + goto out; + } m->m_len = outlen; md = mtod(m, void *);
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