From nobody Tue Nov 07 13:39:00 2023 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4SPq7S2sTpz506l9; Tue, 7 Nov 2023 13:39:00 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4SPq7S2Ll3z4Sjt; Tue, 7 Nov 2023 13:39:00 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1699364340; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=L8kgXhOFPXmV0rVK7yHJ2+SvmMDRyBmoKDnpZc2cJX8=; b=YUVzGK1dJND4T87/sjtrGndUtVJIyK2ZYgPJnUO7NnNgFd9o6DjK74oyorMIQX6dTUtzQu 7aL1JTnPE2DmzYpoflJv6deGAAbdq8LwdCi7T68/KwN0idf92Kl413dA0M7w9OZcdlS8VJ cOSCfOxKvGi1bbhOQ5PmjDJS/mtXa2oWn+Pgu1Q7HBV3jutmAMWJgy8TL9Trf/LUm+xwug Xl/hH3mS/r7mFuwoc7bsSurbmElu9TZvIgVpqGX+LaaGhqTVyBjrIwMRGrFlIu8UHInEA4 5kd7HDKH++f9qFqcXCSG33fx/ibA6IaOicW5tdOB0+UOtwTHu5Y46FLszy2KZw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1699364340; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=L8kgXhOFPXmV0rVK7yHJ2+SvmMDRyBmoKDnpZc2cJX8=; b=YutfQt8//QJHeFmhYyxNakMlB1+MSY+MDvaXVxyAsnoDIyxifyWyEjc/hQHzubLTVQGBcl DASbqVPCl/a+rU3pIFXcYh7rGVhoqO//8O99sTi+AnSmYkwVgUS/Eib3zd8WgTizRnsrYG FaXP3da7OR3/pCFP+6ntSS90m8qEY72ic/SAqJheAqxOSL288vdQrPTH1v9fO2vTY8V8vS mLeW/AGX0hnOef/9K9N8PLAYkKLdzXn4wpNNjZxCg4Lg30vNEU3C1YM86ZtYalyXQshCXJ /g7wuERqiJOIaENQxhxKmkR4FVmGU2TbLCucLx+J2ajn5FrId5aRYFe1larkmQ== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1699364340; a=rsa-sha256; cv=none; b=sMWKUntAEIrQgF1zPeF0UWX+ji9GE/N9vS6mli0IMdGxAo8krf8lmzsqSzNVRvZSUCbj5l eetOwfoLIzC3R11jrAb21HftWtt4We42WdcUs/1kXXcbfNJfc8aidFfsrP9THyyKbpTeVZ HWL+d/lRcchjsMqh2wmW4oORGlllSitUFFWZeFA+RlboqnX/JqgK/svFBoXiXp67Gi9HwK 5aKuWqjDiR+jkrSOVAJM9CM1ty/ongpQMLAbDviHkDiOujLJl6F7v4pmvFmsVQe3Zbn92q bmuCPwcHRThwFHvq67Pw2PLHSrVsFLlcekxocSYJTpdWmXNG1rfoBpigr5F0yQ== Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4SPq7S1SBBzrnm; Tue, 7 Nov 2023 13:39:00 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.17.1/8.17.1) with ESMTP id 3A7Dd0db052154; Tue, 7 Nov 2023 13:39:00 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.17.1/8.17.1/Submit) id 3A7Dd0lg052151; Tue, 7 Nov 2023 13:39:00 GMT (envelope-from git) Date: Tue, 7 Nov 2023 13:39:00 GMT Message-Id: <202311071339.3A7Dd0lg052151@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org From: Ed Maste Subject: git: 92709431b14d - stable/14 - fflush: correct buffer handling in __sflush List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-all@freebsd.org X-BeenThere: dev-commits-src-all@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: emaste X-Git-Repository: src X-Git-Refname: refs/heads/stable/14 X-Git-Reftype: branch X-Git-Commit: 92709431b14df6c0687446247ac57cfc189ee827 Auto-Submitted: auto-generated The branch stable/14 has been updated by emaste: URL: https://cgit.FreeBSD.org/src/commit/?id=92709431b14df6c0687446247ac57cfc189ee827 commit 92709431b14df6c0687446247ac57cfc189ee827 Author: Dag-Erling Smørgrav AuthorDate: 2023-08-03 15:13:45 +0000 Commit: Ed Maste CommitDate: 2023-11-07 13:38:24 +0000 fflush: correct buffer handling in __sflush This fixes CVE-2014-8611 correctly. The commit that purported to fix CVE-2014-8611 (805288c2f062) only hid it behind another bug. Two later commits, 86a16ada1ea6 and 44cf1e5eb470, attempted to address this new bug but mostly just confused the issue. This commit rolls back the three previous changes and fixes CVE-2014-8611 correctly. The key to understanding the bug (and the fix) is that `_w` has different meanings for different stream modes. If the stream is unbuffered, it is always zero. If the stream is fully buffered, it is the amount of space remaining in the buffer (equal to the buffer size when the buffer is empty and zero when the buffer is full). If the stream is line-buffered, it is a negative number reflecting the amount of data in the buffer (zero when the buffer is empty and negative buffer size when the buffer is full). At the heart of `fflush()`, we call the stream's write function in a loop, where `t` represents the return value from the last call and `n` the amount of data that remains to be written. When the write function fails, we need to move the unwritten data to the top of the buffer (unless nothing was written) and adjust `_p` (which points to the next free location in the buffer) and `_w` accordingly. These variables have already been set to the values they should have after a successful flush, so instead of adjusting them down to reflect what was written, we're adjusting them up to reflect what remains. The bug was that while `_p` was always adjusted, we only adjusted `_w` if the stream was fully buffered. The fix is to also adjust `_w` for line-buffered streams. Everything else is just noise. Fixes: 805288c2f062 Fixes: 86a16ada1ea6 Fixes: 44cf1e5eb470 Sponsored by: Klara, Inc. (cherry picked from commit d09a3bf72c0b5f1779c52269671872368c99f02a) Approved by: so --- lib/libc/stdio/fflush.c | 21 +++++++-------------- lib/libc/stdio/fvwrite.c | 4 ++-- lib/libc/stdio/wbuf.c | 2 +- 3 files changed, 10 insertions(+), 17 deletions(-) diff --git a/lib/libc/stdio/fflush.c b/lib/libc/stdio/fflush.c index 7ad6adedf53f..61f23335106f 100644 --- a/lib/libc/stdio/fflush.c +++ b/lib/libc/stdio/fflush.c @@ -103,8 +103,8 @@ __weak_reference(__fflush, fflush_unlocked); int __sflush(FILE *fp) { - unsigned char *p, *old_p; - int n, f, t, old_w; + unsigned char *p; + int n, f, t; f = fp->_flags; if ((f & __SWR) == 0) @@ -119,26 +119,19 @@ __sflush(FILE *fp) * Set these immediately to avoid problems with longjmp and to allow * exchange buffering (via setvbuf) in user write function. */ - old_p = fp->_p; fp->_p = p; - old_w = fp->_w; fp->_w = f & (__SLBF|__SNBF) ? 0 : fp->_bf._size; for (; n > 0; n -= t, p += t) { t = _swrite(fp, (char *)p, n); if (t <= 0) { - /* Reset _p and _w. */ - if (p > fp->_p) { + if (p > fp->_p) /* Some was written. */ memmove(fp->_p, p, n); - fp->_p += n; - if ((fp->_flags & (__SLBF | __SNBF)) == 0) - fp->_w -= n; - /* conditional to handle setvbuf */ - } else if (p == fp->_p && errno == EINTR) { - fp->_p = old_p; - fp->_w = old_w; - } + /* Reset _p and _w. */ + fp->_p += n; + if ((fp->_flags & __SNBF) == 0) + fp->_w -= n; fp->_flags |= __SERR; return (EOF); } diff --git a/lib/libc/stdio/fvwrite.c b/lib/libc/stdio/fvwrite.c index 81e7ba89a644..26245acca1c9 100644 --- a/lib/libc/stdio/fvwrite.c +++ b/lib/libc/stdio/fvwrite.c @@ -139,7 +139,7 @@ __sfvwrite(FILE *fp, struct __suio *uio) fp->_p += w; old_p = fp->_p; if (__fflush(fp) == EOF) { - if (old_p == fp->_p && errno == EINTR) + if (old_p == fp->_p) fp->_p -= w; goto err; } @@ -183,7 +183,7 @@ __sfvwrite(FILE *fp, struct __suio *uio) fp->_p += w; old_p = fp->_p; if (__fflush(fp) == EOF) { - if (old_p == fp->_p && errno == EINTR) + if (old_p == fp->_p) fp->_p -= w; goto err; } diff --git a/lib/libc/stdio/wbuf.c b/lib/libc/stdio/wbuf.c index acbe379ad90e..808cfa588cfb 100644 --- a/lib/libc/stdio/wbuf.c +++ b/lib/libc/stdio/wbuf.c @@ -89,7 +89,7 @@ __swbuf(int c, FILE *fp) old_p = fp->_p; if (++n == fp->_bf._size || (fp->_flags & __SLBF && c == '\n')) { if (__fflush(fp) != 0) { - if (fp->_p == old_p && errno == EINTR) { + if (fp->_p == old_p) { fp->_p--; fp->_w++; }