Date: Tue, 6 Feb 2024 18:11:01 GMT From: Kyle Evans <kevans@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: a8aa5ba3db69 - stable/14 - kern: tty: fix ttyinq_read_uio assertion Message-ID: <202402061811.416IB1jB044439@gitrepo.freebsd.org>
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The branch stable/14 has been updated by kevans: URL: https://cgit.FreeBSD.org/src/commit/?id=a8aa5ba3db694f97d21e946d6392c527af31f05b commit a8aa5ba3db694f97d21e946d6392c527af31f05b Author: Kyle Evans <kevans@FreeBSD.org> AuthorDate: 2024-01-16 02:55:58 +0000 Commit: Kyle Evans <kevans@FreeBSD.org> CommitDate: 2024-02-06 15:31:17 +0000 kern: tty: fix ttyinq_read_uio assertion It's clear from later context that `rlen` was always expected to include `flen`, as we'll trim `flen` bytes from the end of the read. Relax our initial assertion to only require the total size less trimmed bytes to lie within the out buffer size. While we're here, I note that if we have to read more than one block and we're trimming from the end then we'll do the wrong thing and omit `flen` bytes from every block, rather than just the end. Add an assertion to make sure we're not doing that, but the only caller that specifies a non-zero `flen` today will only really be doing so if rlen is entirely within a single buffer. Reviewed by: cy, imp (cherry picked from commit 09a43b8790bdeb97fbecd3ea767c2f599eb4a4d3) --- sys/kern/tty_inq.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/sys/kern/tty_inq.c b/sys/kern/tty_inq.c index daf3bde77712..0bf7c2fa5b5e 100644 --- a/sys/kern/tty_inq.c +++ b/sys/kern/tty_inq.c @@ -165,7 +165,8 @@ ttyinq_read_uio(struct ttyinq *ti, struct tty *tp, struct uio *uio, size_t rlen, size_t flen) { - MPASS(rlen <= uio->uio_resid); + /* rlen includes flen, flen bytes will be trimmed from the end. */ + MPASS(rlen - flen <= uio->uio_resid); while (rlen > 0) { int error; @@ -192,6 +193,14 @@ ttyinq_read_uio(struct ttyinq *ti, struct tty *tp, struct uio *uio, MPASS(clen >= flen); rlen -= clen; + /* + * Caller shouldn't request that we trim anything if we might be + * reading across blocks. We could handle it, but today we do + * not. + */ + if (flen > 0) + MPASS(rlen == 0); + /* * We can prevent buffering in some cases: * - We need to read the block until the end.
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