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=1793831714; b=4LFA/qAA2+e6hgxL6UNTAAZ4kC1mBJBUm3htivdaovQ+Kbx1BhG4a6TokkIIpEsbF8qA erfN3pMQs30B6i9O4vl4Pm8rbDIbkdKouAI+XfynYJSB90vrq31jZAzy6BSemU0j0vB3m 05TjjpI9kCfVnJ2/Cg1iHHi+6zMYBN/vwhgNLFnmS5eF+vQznUowXp6ckvczbrEbNWUW3 7upLbD5pJdAJVJ86dmDkI7sfL+MocGzPWTdux0u5MJkJUHjHGAasr7eHPJDrRu+t0kXvb 0/78hgE4CPfU0NT67mVLF0z4Do4vj6p2wKw1cPEnVsUhPoQL9DYtlasPjNBYAY2BV7A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793831714; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=9E8D/i0q9l8Nz93MJrbv/L8iF8UTYPCv5J1zLF0zpnc=; b=R3M97RGZhQV0zL6UEz2ZnWVPF2hR8dWoEgfp3aS93r1P7ZX0vEX+nhK1WX0Jelag8Ov5 QNsuDP1U+uFa7us1VRC3itIbOCBe0oo8Yh/Qv8zXLJ80JcCf/a8PuZzaLzUbzJwuWasO3 Elb3UC4og2gyLGLuas/JgSLPgddjD4ucHB+tJ1wHQkU5QlP2oRogAT/qEZGspcGJfFvDG WCXwC3BbC0mHHBHxjMgmAzy1d+99khLMhI99Gd4s3OA2QbrzPXXFSkHZ7aWrlrWt5wkNU UOVXkS6jF6mZiE7nbhdorWDDyp0U6nUaK3xWVlmccI9rynO3YV45NrrYv++oCX9kpCQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=lzFKnhr+; 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 0B75B606A337; Wed, 4 Nov 2026 22:35:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=lzFKnhr+ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98C411F000C1; Wed, 4 Nov 2026 22:35:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793831713; bh=9E8D/i0q9l8Nz93MJrbv/L8iF8UTYPCv5J1zLF0zpnc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lzFKnhr+wzMfdQF1V+rfFB/fzktoN+YU91dLcg/SLBXkHlIpUc/osXG8eIEFwnC7Y oitc3/aGd8SsSU5fiX30xsNX/cSgq5YDAttIWXPfbBQ7/DMt8KxGSVGg3ybT8Bl4+9 kazM83+Qz0UPFtcdIK+SR1Rw04tGfgXcaQQQHTwQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Xin Liu , Paulo Alcantara , Luxiao Xu , Ren Wei Subject: [PATCH 6.18 0868/1005] smb: client: fix buffer overflow in SMB2_tcon() Date: Wed, 4 Nov 2026 16:10:01 -0500 Message-ID: <20261104211107.582637249@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Luxiao Xu commit 73cc469b0ff7551f8537ea919709973e6dc4f514 upstream. In SMB2_tcon(), unc_path is allocated with a fixed buffer size of MAX_SHARENAME_LENGTH * 2 bytes (672 bytes). However, the user-controlled UNC path (tree) length is passed to cifs_strtoUTF16(), which assumes the destination buffer is large enough and writes strlen(tree) + 1 UTF-16 code units. Commit 62a1a439e0fd ("cifs: clean up handling of unc= option") removed the length check on UNC mount options, allowing mount paths to exceed MAX_SHARENAME_LENGTH while retaining the fixed-size buffer allocation in SMB2_tcon(). Consequently, an oversized UNC string causes cifs_strtoUTF16() to write past the end of the heap object, resulting in a slab-out-of-bounds write. Furthermore, if a tree exceeds MAX_TREE_SIZE characters, strscpy() truncates it in cifs_tcon::tree_name, causing subsequent reconnects or failovers to fail. Fix this by first verifying that the length of tree does not exceed MAX_TREE_SIZE, returning -EINVAL if it does. Then, dynamically allocate unc_path based on the length of tree so that it safely accommodates all UTF-16 code units for paths within MAX_TREE_SIZE. Fixes: 62a1a439e0fd ("cifs: clean up handling of unc= option") Cc: stable@vger.kernel.org Reported-by: Xin Liu Closes: https://bugtracker.nebusec.ai/f/3292 Assisted-by: LLM Suggested-by: Paulo Alcantara Signed-off-by: Luxiao Xu Signed-off-by: Ren Wei [pc: remove unused MAX_SHARENAME_LENGTH] Signed-off-by: Paulo Alcantara Signed-off-by: Greg Kroah-Hartman --- fs/smb/client/smb2pdu.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- a/fs/smb/client/smb2pdu.c +++ b/fs/smb/client/smb2pdu.c @@ -2017,8 +2017,6 @@ static inline void cifs_stats_fail_inc(s cifs_stats_inc(&tcon->stats.smb2_stats.smb2_com_failed[code]); } -#define MAX_SHARENAME_LENGTH (255 /* server */ + 80 /* share */ + 1 /* NULL */) - /* These are similar values to what Windows uses */ static inline void init_copy_chunk_defaults(struct cifs_tcon *tcon) { @@ -2049,7 +2047,15 @@ SMB2_tcon(const unsigned int xid, struct if (!server || !tree) return -EIO; - unc_path = kmalloc(MAX_SHARENAME_LENGTH * 2, GFP_KERNEL); + total_len = strlen(tree); + if (total_len > MAX_TREE_SIZE) { + cifs_server_dbg(VFS | ONCE, + "%s: tree name exceeded %u characters\n", + __func__, MAX_TREE_SIZE); + return -EINVAL; + } + + unc_path = kmalloc((total_len + 1) * sizeof(*unc_path), GFP_KERNEL); if (unc_path == NULL) return -ENOMEM;