From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f47.google.com (mail-pj1-f47.google.com [209.85.216.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7F83B45D91E for ; Thu, 15 Oct 2026 06:19:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792045168; cv=none; b=m59fBK1kDrboPKkGycyQgyX1jE4P5qgX9ZL28r8mh1mVncKetNeT+Go8uBUrlG7n4+Ae7VHcTp+ahTog6qnVbvDhThz0wg0OI2Lh6MAVK68WOSY+ffkWT8d9IcF08rXtvAH3c6cG2nqayyGYCAvRJCq6Hv0rZNtSgs7jaRMlhmo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792045168; c=relaxed/simple; bh=SnTqnSHnJf1SyEgRppnLJtdvwZ/K9QpTpMoFZTST/So=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=cnrYqTPGrID3kvo2qse6+ecIeuYl775HszLnI8k5sYtReipIWmxNgDGP87/SJo6y5VHrATciPd6LmldN99LXo6dLPpLICgsylq1bekAH3pYLKrURSmpuXUz8qK3XymZgGN7lUlQf+V8wj5OeDzuOqzHHvzN4i56QpElT7l5Qcl4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=eMsEg9vs; arc=none smtp.client-ip=209.85.216.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="eMsEg9vs" Received: by mail-pj1-f47.google.com with SMTP id 98e67ed59e1d1-3ac9f49b984so154923a91.1 for ; Wed, 14 Oct 2026 23:19:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1792045164; x=1792649964; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to:content-type; bh=LKqK4HrH78W1MTYoSkDNokUsDBo14132TDZJAUlwXh8=; b=eMsEg9vsgz4JpZA/dQGmcIu7cuJhRpTt9bfXp/QLtE6wYb3AwFvj5xjTWMPOs90pPc jE6uZFmpKp104w+kZDOf7V5ZRLT2gpxeYShesAyn4HMOtY1iyWj3X60jla8tnX/Zy+9A 1UR4iR8QOfZAmT6e5EXxja16F8HF8rUeJ6/M4OOztB9SNkCXc3CMVGph4MpXZwJ10v1j SOa8zryzSZrFcdBgxRsIpOyN9GtV/KNfzEne6ZnZSSJlN0TabAn+Q5nC+ExwBe33LoKW dpKAXHFm5eyP0BZv0aA2kmpJOn/vkmq2fvo7ikaX72ed9z4THTsBc2YHQwE4B2y1JeYm UhVg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792045164; x=1792649964; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=LKqK4HrH78W1MTYoSkDNokUsDBo14132TDZJAUlwXh8=; b=NCyRqu9k6HOLvZ/Gt7+8Usy3mjAFv+kJPO4wBM5vxJhr7V8tZ56cuZb+HDK3u7zX2A eEp5QbfNswYPTV5ZsXfAuoF+e+NALpXZsy9t+7bqjOsE1mVr4ebufRNCUvXcYcwhZ2Ro s18lR6hZXSNT51pjqTkjQiRvd40sWiP5mvUSZJDnKY2S/kk9dKh/9W1YNVO/41oBeHY7 nLsKXkuUr0ji+MPXdECf6bBF9J6dmEXlKsVXLoaFN1RLTq0FUIjpPW5t3ESNoFpysau1 w16uTUqR2I0WEmmbaNPFPck9+qjIl2wwCuEPcdMrBX/00uR+Ozus+3RgRZuPNpve63fF 2ssg== X-Forwarded-Encrypted: i=1; AKwUvBz8JsLGvoxNaP1LhMOwhLvDq7DYoc5vAfvRNgcOpa/vlFo1q8sHp4v4PF6yzw2C/a/phfv9aqtMeahMpA==@vger.kernel.org X-Gm-Message-State: AFq9FYLwfnfKP/Exd51LAoBb4RUxwcbVoMVmeujbmy0BCfGwHlsfpRWp m6PAr5/CIL9Pt00706wGK6OAEE+4SJ3JDB4fFaWjpZKS40Hv0OpNx46D X-Gm-Gg: AYBFou1phTb9LdvtIOGujYEI6b0UejzXDGA2oKv4T3D4DaZokzXp05R1LbBj2qFAVuM u/Z1a4qQsYQlSZTgFVkPQCLRDHBMkuothn2C1Wij7YcFyEHG/RBQqO6vqYHHyyEsyU/wH81FQ+X SbbyQRP9xYwpVKuNtev6xAf7dx6etUwIg1lUpfssUPkNszGr+iju2bgg4fWSSGxJMqCeCVqSA6E TrXL/3mL0lqpN46m7T4R+hanv7Z64epoJeJTNzpjLsR4z9OsWisnpUSzADgXWdXLJ9Q7PXUk+fO LwCSvsG6C2xGuw+Ecl3hquHpDjpahfgmOTsaW7fzp6oHpfxB36sWYz4kqHva6g4oCqJ7ccyliMk ImZrzeLbUOo3RJMItGNKFvlnVHSefmNc86njPjjlsMqvHNbo+5rziAu07cmrLFdCxEQgpg/vokN HyySrPj3Jwf9vqqC//v2HCN2L4ipTfcIdCRpd5333gZzD7LsZLYi9NwKuh85YJG8T8X7pYz5Bad RtUtS7zLU8y X-Received: by 2002:a17:90b:4b:b0:3a7:96d:feaf with SMTP id 98e67ed59e1d1-3ab3a9a0c59mr9385893a91.16.1792045163419; Wed, 14 Oct 2026 23:19:23 -0700 (PDT) Received: from ancienth-X870E-Nova-WiFi ([125.186.72.2]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ac9461d71esm2669111a91.7.2026.10.14.23.19.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Oct 2026 23:19:22 -0700 (PDT) From: Daehyeon Ko <4ncienth@gmail.com> To: Alexander Viro , Andrew Morton , Jens Axboe Cc: Keith Busch , Hannes Reinecke , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Daehyeon Ko <4ncienth@gmail.com> Subject: [PATCH v2] iov_iter: validate extracted segment for bvec alignment Date: Thu, 15 Oct 2026 15:19:07 +0900 Message-ID: <20261015061907.2713943-1-4ncienth@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit iov_iter_extract_bvecs() validates iter_iov_addr() and iter_iov_len() before iov_iter_extract_pages() selects the first nonempty segment and limits it by iter->count. The checks can therefore cover a different range after a leading empty segment or iov_iter_truncate(). An unprivileged O_DIRECT preadv() reproduced the empty-segment case: an aligned empty segment followed by a misaligned one completed 4096 bytes instead of returning -EINVAL. A truncated iterator has the same mismatch when its full segment length is aligned but its remaining count is not. Bound the normal fast-path length by iter->count. Keep first_iovec_segment() for leading empty segments so validation covers the remaining portion of the segment available for extraction. Closes: https://lore.kernel.org/r/20261012065520.1089147-1-4ncienth@gmail.com Fixes: 14b007e17881 ("block: validate user space vectors during extraction") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Daehyeon Ko <4ncienth@gmail.com> --- Changes in v2: - Bound the normal fast-path length by iter->count while retaining first_iovec_segment() for leading empty segments. - Cover the truncated-iterator case raised by Andrew Morton and Sashiko. v1: https://lore.kernel.org/r/20261012065520.1089147-1-4ncienth@gmail.com lib/iov_iter.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 2072c04e99d052..d21082fb251bf7 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1022,7 +1022,7 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i, return maxsize; } -/* must be done on non-empty ITER_UBUF or ITER_IOVEC one */ +/* must be used on a non-empty ITER_UBUF, ITER_IOVEC or ITER_KVEC */ static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size) { size_t skip; @@ -1938,8 +1938,13 @@ ssize_t iov_iter_extract_bvecs(struct iov_iter *iter, struct bio_vec *bv, iter_is_iovec(iter) || iov_iter_is_kvec(iter))) { unsigned long start = (unsigned long)iter_iov_addr(iter); + size_t seg_size = min(iter_iov_len(iter), iter->count); - if ((start | iter_iov_len(iter)) & mem_align_mask) + if (unlikely(!seg_size && iter->count)) { + seg_size = iter->count; + start = first_iovec_segment(iter, &seg_size); + } + if ((start | seg_size) & mem_align_mask) return -EINVAL; } else if (iov_iter_alignment(iter) & mem_align_mask) { return -EINVAL; base-commit: 72d3fcf802c45d00b300f25b848a93c3a2bd7c7e -- 2.55.0