From 729c0c9dd55204f0c9a823ac8a7bfa83d36c7e78 Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Thu, 5 Jul 2018 15:10:02 +0200 Subject: cifs: Fix stack out-of-bounds in smb{2,3}_create_lease_buf() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit smb{2,3}_create_lease_buf() store a lease key in the lease context for later usage on a lease break. In most paths, the key is currently sourced from data that happens to be on the stack near local variables for oplock in SMB2_open() callers, e.g. from open_shroot(), whereas smb2_open_file() properly allocates space on its stack for it. The address of those local variables holding the oplock is then passed to create_lease_buf handlers via SMB2_open(), and 16 bytes near oplock are used. This causes a stack out-of-bounds access as reported by KASAN on SMB2.1 and SMB3 mounts (first out-of-bounds access is shown here): [ 111.528823] BUG: KASAN: stack-out-of-bounds in smb3_create_lease_buf+0x399/0x3b0 [cifs] [ 111.530815] Read of size 8 at addr ffff88010829f249 by task mount.cifs/985 [ 111.532838] CPU: 3 PID: 985 Comm: mount.cifs Not tainted 4.18.0-rc3+ #91 [ 111.534656] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 111.536838] Call Trace: [ 111.537528] dump_stack+0xc2/0x16b [ 111.540890] print_address_description+0x6a/0x270 [ 111.542185] kasan_report+0x258/0x380 [ 111.544701] smb3_create_lease_buf+0x399/0x3b0 [cifs] [ 111.546134] SMB2_open+0x1ef8/0x4b70 [cifs] [ 111.575883] open_shroot+0x339/0x550 [cifs] [ 111.591969] smb3_qfs_tcon+0x32c/0x1e60 [cifs] [ 111.617405] cifs_mount+0x4f3/0x2fc0 [cifs] [ 111.674332] cifs_smb3_do_mount+0x263/0xf10 [cifs] [ 111.677915] mount_fs+0x55/0x2b0 [ 111.679504] vfs_kern_mount.part.22+0xaa/0x430 [ 111.684511] do_mount+0xc40/0x2660 [ 111.698301] ksys_mount+0x80/0xd0 [ 111.701541] do_syscall_64+0x14e/0x4b0 [ 111.711807] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 111.713665] RIP: 0033:0x7f372385b5fa [ 111.715311] Code: 48 8b 0d 99 78 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 66 78 2c 00 f7 d8 64 89 01 48 [ 111.720330] RSP: 002b:00007ffff27049d8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5 [ 111.722601] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f372385b5fa [ 111.724842] RDX: 000055c2ecdc73b2 RSI: 000055c2ecdc73f9 RDI: 00007ffff270580f [ 111.727083] RBP: 00007ffff2705804 R08: 000055c2ee976060 R09: 0000000000001000 [ 111.729319] R10: 0000000000000000 R11: 0000000000000206 R12: 00007f3723f4d000 [ 111.731615] R13: 000055c2ee976060 R14: 00007f3723f4f90f R15: 0000000000000000 [ 111.735448] The buggy address belongs to the page: [ 111.737420] page:ffffea000420a7c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0 [ 111.739890] flags: 0x17ffffc0000000() [ 111.741750] raw: 0017ffffc0000000 0000000000000000 dead000000000200 0000000000000000 [ 111.744216] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 [ 111.746679] page dumped because: kasan: bad access detected [ 111.750482] Memory state around the buggy address: [ 111.752562] ffff88010829f100: 00 f2 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 [ 111.754991] ffff88010829f180: 00 00 f2 f2 00 00 00 00 00 00 00 00 00 00 00 00 [ 111.757401] >ffff88010829f200: 00 00 00 00 00 f1 f1 f1 f1 01 f2 f2 f2 f2 f2 f2 [ 111.759801] ^ [ 111.762034] ffff88010829f280: f2 02 f2 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 [ 111.764486] ffff88010829f300: f2 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 111.766913] ================================================================== Lease keys are however already generated and stored in fid data on open and create paths: pass them down to the lease context creation handlers and use them. Suggested-by: Aurélien Aptel Reviewed-by: Aurelien Aptel Fixes: b8c32dbb0deb ("CIFS: Request SMB2.1 leases") Signed-off-by: Stefano Brivio Signed-off-by: Steve French --- fs/cifs/smb2pdu.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'fs/cifs/smb2pdu.c') diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index e31375ecaa6f..3c92678cb45b 100644 --- a/fs/cifs/smb2pdu.c +++ b/fs/cifs/smb2pdu.c @@ -1716,12 +1716,12 @@ parse_lease_state(struct TCP_Server_Info *server, struct smb2_create_rsp *rsp, static int add_lease_context(struct TCP_Server_Info *server, struct kvec *iov, - unsigned int *num_iovec, __u8 *oplock) + unsigned int *num_iovec, u8 *lease_key, __u8 *oplock) { struct smb2_create_req *req = iov[0].iov_base; unsigned int num = *num_iovec; - iov[num].iov_base = server->ops->create_lease_buf(oplock+1, *oplock); + iov[num].iov_base = server->ops->create_lease_buf(lease_key, *oplock); if (iov[num].iov_base == NULL) return -ENOMEM; iov[num].iov_len = server->vals->create_lease_size; @@ -2181,7 +2181,8 @@ SMB2_open(const unsigned int xid, struct cifs_open_parms *oparms, __le16 *path, *oplock == SMB2_OPLOCK_LEVEL_NONE) req->RequestedOplockLevel = *oplock; else { - rc = add_lease_context(server, iov, &n_iov, oplock); + rc = add_lease_context(server, iov, &n_iov, + oparms->fid->lease_key, oplock); if (rc) { cifs_small_buf_release(req); kfree(copy_path); -- cgit v1.2.3