From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794437404; b=vZlXry/JbJNQ4PLOo+BwTPf3z26dzXrPNrNWk1qk7UBclcoPvhMF05OstUkrmVeultOf dQglkdliRSj0Lu+iTQhPov5xJ2hpx09Ph7iDyiGZjX5VS1HisQcxOjfvJxYv/0OthUtUa DhszgRNalvijz8vZFQZGvtfkAkowBjhqo/R/uFMTfxP37zLBx/5G/U1dS5BfIzAwa9StJ 4re7o+ZV553CGjdnKR2JlD43Wyw1Hl1X0v06IzWpWfNGwS/ilxZKFeejitnr7tTiZeux1 tNyKbgdWW576Qjl6LnStaFzF4SRgcm32BHFH0UWz71g1lxO7hNij6wGyw4YhQyy4uyg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794437404; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=uvuWkmR5cSVG5819SAj7bOcVR2rL3YncXgbCnmeAeNs=; b=d0vkZ5qFojaBw0lor68ahDbJigLFcOCaE6QZx5O9KxZ4J0w5RGyz31AcSuGGXbn67cYW C8StnOICSvgQi/e8esZdVJwvhxsuJVtXSn14ZRRjp46pdAXWH8M0GTIQUmorqL3MJTkNt 8ANrgNSMhJoT9VTRPStD4nBkN91NzV5+7+J+/qfQnk1NBoF/cB0sgGaw4e9t/a5L9m6em Kj+6hMoKUSwAlY/T29GHfqzEMumLWCeoqc1e8KQAkOGO5o9o+9mCmOGDuH8vwioX/UBNy UNDh2Qnn0IjnbsJE6sfuoEIBpgNzVFJKfI5E/8fWUNtsuZmuLriJ7LNnl7Cai/q0kWw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=jQ+vQW0m; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BA147606A324 for ; Wed, 11 Nov 2026 22:50:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=jQ+vQW0m Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0CF931F00A05; Wed, 11 Nov 2026 22:50:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794437404; bh=uvuWkmR5cSVG5819SAj7bOcVR2rL3YncXgbCnmeAeNs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=jQ+vQW0mXJf5PH18ebeQV8ZBCBSngs8ImPymVu9RBHdkEcYuIWPTHoS3UGeVURBo6 /2zKNDxsoIeEksDJL1Bno/tRE/bFR4DLry9Xmer9fWT5dAt9840bFsRhd9SVA4zebc Lb+9yyBvUE6skspJlr3bu7blyuxxoHyXLV3PGYXvJwCVNGO931rxghDjCEXK0pPPR2 JKV7brfuu5/1PewwkZuA08PWoK4x6L+wDD7ZtYbzBMamg0duj/574lnuY3M2DxSU2W 0IyJn6xpujTc8m2O6mMtXy7kr5/uH0fnGLw+zpAJwBPHEXcnhBIomhKfghbqGWSJPT E06OkHfVEDHiw== From: Sasha Levin To: stable@vger.kernel.org Cc: Jake Labelle , Ryusuke Konishi , Viacheslav Dubeyko , Sasha Levin Subject: [PATCH 6.1.y] nilfs2: validate directory position after llseek in readdir Date: Wed, 11 Nov 2026 17:50:02 -0500 Message-ID: <20261111224938.251235-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107054541-failed-6.1-de7f49c12566@kernel.org> References: <20261107054541-failed-6.1-de7f49c12566@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jake Labelle [ Upstream commit de7f49c12566cc5c7437a2f26c6c754b9d4d5648 ] nilfs_readdir() uses ctx->pos, which userspace can set to an arbitrary value via llseek, as an offset into the directory folio and parses whatever bytes sit there as a directory entry. A position pointing into the middle of an entry -- or at unused bytes of a corrupted image that the page validator never inspected -- makes dir_emit() copy up to 255 (name_len) bytes from a bogus entry, possibly reading past the end of the folio and returning unrelated memory contents to userspace. Snap unaligned positions onto a valid entry boundary by walking the rec_len chain from the chunk start before parsing, as ext2 does in ext2_validate_entry(). [ryusuke: fixed offset wrap-around in nilfs_validate_entry() and conformed AI tag to guidelines] Fixes: 2ba466d74ed7 ("nilfs2: directory entry operations") Assisted-by: Claude:claude-mythos-5 Signed-off-by: Jake Labelle Cc: stable@vger.kernel.org Signed-off-by: Ryusuke Konishi Signed-off-by: Viacheslav Dubeyko [ sashal: adjusted helper insertion context to follow nilfs_set_de_type() instead of nilfs_next_entry() ] Signed-off-by: Sasha Levin --- fs/nilfs2/dir.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c index 0f3753af16741..0c68db4e4bd53 100644 --- a/fs/nilfs2/dir.c +++ b/fs/nilfs2/dir.c @@ -265,11 +265,27 @@ static void nilfs_set_de_type(struct nilfs_dir_entry *de, struct inode *inode) de->file_type = nilfs_type_by_mode[(mode & S_IFMT)>>S_SHIFT]; } +static inline unsigned int +nilfs_validate_entry(char *base, unsigned int offset, unsigned int mask) +{ + struct nilfs_dir_entry *de = (struct nilfs_dir_entry *)(base + offset); + struct nilfs_dir_entry *p = + (struct nilfs_dir_entry *)(base + (offset & mask)); + + while ((char *)p < (char *)de) { + if (p->rec_len == 0) + break; + p = nilfs_next_entry(p); + } + return (char *)p - base; +} + static int nilfs_readdir(struct file *file, struct dir_context *ctx) { loff_t pos = ctx->pos; struct inode *inode = file_inode(file); struct super_block *sb = inode->i_sb; + unsigned int chunk_size = nilfs_chunk_size(inode); unsigned int offset = pos & ~PAGE_MASK; unsigned long n = pos >> PAGE_SHIFT; unsigned long npages = dir_pages(inode); @@ -288,6 +304,24 @@ static int nilfs_readdir(struct file *file, struct dir_context *ctx) ctx->pos += PAGE_SIZE - offset; return -EIO; } + /* + * ctx->pos comes from userspace via llseek and may point + * into the middle of an entry -- or at unvalidated bytes + * of a crafted image. offset is only nonzero here on the + * very first iteration (subsequent pages always start at + * offset 0, which -- like any chunk boundary -- is always + * a legitimate entry start, since no rec_len chain crosses + * a chunk boundary). Snap a non-chunk-aligned offset onto + * a real entry boundary by walking the chain from the + * enclosing chunk's start, as ext2 does; otherwise + * dir_emit() copies name_len bytes from a fake entry, + * reading past the end of the folio. + */ + if (offset & (chunk_size - 1)) { + offset = nilfs_validate_entry(kaddr, offset, + ~(chunk_size - 1)); + ctx->pos = ((loff_t)n << PAGE_SHIFT) + offset; + } de = (struct nilfs_dir_entry *)(kaddr + offset); limit = kaddr + nilfs_last_byte(inode, n) - NILFS_DIR_REC_LEN(1); -- 2.53.0