From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D573B3D2FF4 for ; Mon, 27 Jul 2026 21:00:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785186016; cv=none; b=SmxHKGB2ovlMLK1XgV25pvhMKA9C+V3gyc8Yo5mcb9pRPNUYQ5LZJLFtLdfNoD/FMKCf7dyuSvDucvs9HXmWEO/U5v1DBFbSSRJMtbZgM9J4aSNTAW9xEyTHo84f6mB23JRpFcJy8ojhcnEutC9Ff864en8iRkJc755BXqzQ5z4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785186016; c=relaxed/simple; bh=zm+bDPRWk5bRCFCSZd17wABkFyERCUW/YXykrPvgnFI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=o2/36YczNNlJfZHv1R3AA4iJUM2sqVqylZiZ5kkiH+xMcn+F9XJ5i6xo1TBMP9Zww+w68a02d/9z4hmRQkiqbLaLrVHOsgENp6Ao4Ty0A1xlqAkPd3IbH23SVhISXFGWeKPzphwPwWBpW4kxmlwWK6gCW7pH/jnT8/pzxE17K/8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BU2KVy3T; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BU2KVy3T" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3ED481F00A3A; Mon, 27 Jul 2026 21:00:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785186015; bh=UGQ96ig8ZwWNHOwWgtbILU/tjN1DtsYS4mleySix6VY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BU2KVy3TMWGMs+fAnoiaP43klfQOyAW8z2qRRR1XUBx5wmHZhw3xqIShODhmW03JN 0Cf98jSSZF8ixUjfgY6lNz5GOFrlr61Rw7pkdZa2t2yyG3b8JFYXG2G9nWsW4Yja5M OtMDeKXHuazQAEUFYm2OSEUe+DMykvP1XQNMuoiDDSIHzRIWVUjb924WkZV4eWd8B4 VeQbzxZlcZ53bOcCLYA4+UK9dUECGrQmyZxrorIXD1DaoF8blTJ6h3Mavm6lhZ3AAl UiUjt/mIlll/hDBpP+4gBo9PLNST0r4V6U2b0D8NxhDWXH8+vVtimQkEf39FZvNtYf vyOG+mkC4i61A== From: Sasha Levin To: stable@vger.kernel.org Cc: Mikulas Patocka , Sami Tolvanen , Sasha Levin Subject: [PATCH 6.18.y 4/4] dm-verity: fix buffer overflow in FEC calculation Date: Mon, 27 Jul 2026 17:00:11 -0400 Message-ID: <20260727210011.1929439-4-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260727210011.1929439-1-sashal@kernel.org> References: <2026072004-monitor-wolf-7764@gregkh> <20260727210011.1929439-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Mikulas Patocka [ Upstream commit 31d6e6c0ba8d5a7bd59660035a089307100c5e8e ] There's a buffer overflow in dm-verity-fec: if (neras && *neras <= v->fec->roots) fio->erasures[(*neras)++] = i; This allows *neras to reach roots + 1 (the post-increment pushes it past roots). This value is then passed as no_eras to decode_rs8(). Inside the RS decoder (lib/reed_solomon/decode_rs.c:113-121), the erasure locator polynomial loop writes lambda[j] where j can reach nroots + 1 — one element past the end of lambda[] (which is sized nroots + 1, valid indices 0..nroots). The out-of-bounds write lands on syn[0], corrupting the syndrome buffer. Signed-off-by: Mikulas Patocka Assisted-by: Claude:claude-opus-4-6 Cc: stable@vger.kernel.org Fixes: a739ff3f543a ("dm verity: add support for forward error correction") Reviewed-by: Sami Tolvanen Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin --- drivers/md/dm-verity-fec.c | 4 ++-- drivers/md/dm-verity-fec.h | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c index cebcc8fd25d700..d1e4fbc5a21d9b 100644 --- a/drivers/md/dm-verity-fec.c +++ b/drivers/md/dm-verity-fec.c @@ -250,7 +250,7 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io, (unsigned long long)block, PTR_ERR(bbuf)); /* assume the block is corrupted */ - if (neras && *neras <= v->fec->roots) + if (neras && *neras < v->fec->roots) fio->erasures[(*neras)++] = i; continue; @@ -268,7 +268,7 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io, * skip if we have already found the theoretical * maximum number (i.e. fec->roots) of erasures */ - if (neras && *neras <= v->fec->roots && + if (neras && *neras < v->fec->roots && fec_is_erasure(v, io, want_digest, bbuf)) fio->erasures[(*neras)++] = i; } diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h index 178ecdddbbd310..c19e2d20657284 100644 --- a/drivers/md/dm-verity-fec.h +++ b/drivers/md/dm-verity-fec.h @@ -50,7 +50,7 @@ struct dm_verity_fec { /* per-bio data */ struct dm_verity_fec_io { struct rs_control *rs; /* Reed-Solomon state */ - int erasures[DM_VERITY_FEC_MAX_ROOTS + 1]; /* erasures for decode_rs8 */ + int erasures[DM_VERITY_FEC_MAX_ROOTS]; /* erasures for decode_rs8 */ u8 *output; /* buffer for corrected output */ unsigned int level; /* recursion level */ unsigned int nbufs; /* number of buffers allocated */ -- 2.53.0