From nobody Tue Nov 07 14:29:47 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 4SPrG33625z50G5c; Tue, 7 Nov 2023 14:29:47 +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 4SPrG32bkdz4Zw5; Tue, 7 Nov 2023 14:29:47 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1699367387; 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=F1pmxnMcDDryg0wOf74FHIxvrSVc/Mak5voVMT8v0gE=; b=vdWLx4AsqfIzOBWvGIB8ZEH/SHl7F+fqxjqvQwPaLNxCSOV9mb4/JctagPQ1y7TwvIJF8m HbvGRzdg/sG04HR0TPsmq7+7sls7+kHWBrAlLdfdbJkMroH1N06zH2N0vw7g0xLJAaXCoS FLdEAcvfAublFAK0knGobg6TTCQvGPx17phQqPotn8p1reElTH1hHKCNbLoTd8F4otxg/U qF7ok6XvmwfcQZDL9CDq0WLWy+MbZJZMGLEn4/q8DLlZy1fgamhlTQL31tbNMap3pN+lFM Nr1s9X0w3YudE4VP5ZkxXRBAaw/L7kcJEULkxTjcYCKYD4TpyObb2jsB8PcHrw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1699367387; 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=F1pmxnMcDDryg0wOf74FHIxvrSVc/Mak5voVMT8v0gE=; b=D+4Mw9Viro+zQ6/q9fV9BhuSulgGyAH7kDKb8+C5bBegccwFFq0cNByKXAfqGVKriVQK2f nTtjQkvDTDBSEanAXkTFOEMffaiMK8HMXt0AGtcqguC1A/BumgQVSF1wu0UFlIgXPHrK4k eSsF+cs2vzFMzRGJhId35d5tqbKq3Yqvf46+DzUvXAApHH4+hg+5gqyI93esPUVDGWBhdD BeRfqHRHqc5f4+s8h06V1scwOF8s+KtOv2YKBIme2kuzxa6BC+cC68xSFRqzcskUqjWzuX 0AjH2zUPHw+rH/Mcf98LLDpt8BFAMWU5VMQmN8QZ7/LiBZx10Lc7nChcvpyPdw== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1699367387; a=rsa-sha256; cv=none; b=e4O4ahGW5nDurMk1RXugAOG4wR82dukinubnVdRpP4WwGRXsAIV+C23mhpFTDtZYBKqT5I SUeZvKMdhWBSwkSADyCpbTjdIyXtG1VcpiWN1O5bKtqMyXCKVSw2qT1W4UsgK2o7TguEjp /fl4Difrxm382iLNDNZoTOmXfmzzCL9Sb4rjXt12bP/s7Wap6OiCAgHDLECNm8HgZMfBpj 4IGobXXbZ42tT2Id1Cz4QdvsLs8GYNglYMAlRtUBfHoKImNxpnNJKig6ND26sASPq+0dFU B+RNfPyxY6hMinOJO0VXeX+ohfKMqtAbbomyjZBFjGhx9JAtAEbIQxqppLCC7w== 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 4SPrG31YPBztNV; Tue, 7 Nov 2023 14:29:47 +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 3A7ETloN035860; Tue, 7 Nov 2023 14:29:47 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.17.1/8.17.1/Submit) id 3A7ETlmk035857; Tue, 7 Nov 2023 14:29:47 GMT (envelope-from git) Date: Tue, 7 Nov 2023 14:29:47 GMT Message-Id: <202311071429.3A7ETlmk035857@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: 3a2ea31568c8 - stable/12 - 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/12 X-Git-Reftype: branch X-Git-Commit: 3a2ea31568c81f7b29710abd3d3e1ada2fbeb6c9 Auto-Submitted: auto-generated The branch stable/12 has been updated by emaste: URL: https://cgit.FreeBSD.org/src/commit/?id=3a2ea31568c81f7b29710abd3d3e1ada2fbeb6c9 commit 3a2ea31568c81f7b29710abd3d3e1ada2fbeb6c9 Author: Dag-Erling Smørgrav AuthorDate: 2023-08-03 15:13:45 +0000 Commit: Ed Maste CommitDate: 2023-11-07 14:11:54 +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) (cherry picked from commit 92709431b14df6c0687446247ac57cfc189ee827) (cherry picked from commit 6cb5690b3495741e9ece6f42ba4a85732932aa83) Approved by: so --- lib/libc/stdio/fflush.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/lib/libc/stdio/fflush.c b/lib/libc/stdio/fflush.c index 05e587ecec66..75f145fae6a3 100644 --- a/lib/libc/stdio/fflush.c +++ b/lib/libc/stdio/fflush.c @@ -127,14 +127,13 @@ __sflush(FILE *fp) 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; - } + /* Reset _p and _w. */ + fp->_p += n; + if ((fp->_flags & __SNBF) == 0) + fp->_w -= n; fp->_flags |= __SERR; return (EOF); }