FAILED: patch "[PATCH] smb: client: fix use-after-free in smb2_query_info_compound()" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 5c86919455c1edec99ebd3338ad213b59271a71b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023112451-helpless-variable-cfb0@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

5c86919455c1 ("smb: client: fix use-after-free in smb2_query_info_compound()") 81ba10959970 ("smb: client: prevent new fids from being removed by laundromat") e95f3f744650 ("smb: client: make laundromat a delayed worker")
2da338ff752a ("smb3: do not start laundromat thread when dir leases disabled") 238b351d0935 ("smb3: allow controlling length of time directory entries are cached with dir leases") d14de8067e3f ("cifs: Add a laundromat thread for cached directories")
38c8a9a52082 ("smb: move client and server files to common directory fs/smb") be4fde79812f ("cifs: fix dentry lookups in directory handle cache")
df57109bd50b ("cifs: use tcon allocation functions even for dummy tcon") 8e843bf38f7b ("cifs: return a single-use cfid if we did not get a lease") 66d45ca1350a ("cifs: Check the lease context if we actually got a lease") abdb1742a312 ("cifs: get rid of mount options string parsing")
9fd29a5bae6e ("cifs: use fs_context for automounts")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5c86919455c1edec99ebd3338ad213b59271a71b Mon Sep 17 00:00:00 2001
From: Paulo Alcantara <[email protected]>
Date: Mon, 30 Oct 2023 17:19:56 -0300
Subject: [PATCH] smb: client: fix use-after-free in smb2_query_info_compound()

The following UAF was triggered when running fstests generic/072 with KASAN enabled against Windows Server 2022 and mount options 'multichannel,max_channels=2,vers=3.1.1,mfsymlinks,noperm'

  BUG: KASAN: slab-use-after-free in smb2_query_info_compound+0x423/0x6d0 [cifs]
  Read of size 8 at addr ffff888014941048 by task xfs_io/27534

  CPU: 0 PID: 27534 Comm: xfs_io Not tainted 6.6.0-rc7 #1
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
  rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014
  Call Trace:
   dump_stack_lvl+0x4a/0x80
   print_report+0xcf/0x650
   ? srso_alias_return_thunk+0x5/0x7f
   ? srso_alias_return_thunk+0x5/0x7f
   ? __phys_addr+0x46/0x90
   kasan_report+0xda/0x110
   ? smb2_query_info_compound+0x423/0x6d0 [cifs]
   ? smb2_query_info_compound+0x423/0x6d0 [cifs]
   smb2_query_info_compound+0x423/0x6d0 [cifs]
   ? __pfx_smb2_query_info_compound+0x10/0x10 [cifs]
   ? srso_alias_return_thunk+0x5/0x7f
   ? __stack_depot_save+0x39/0x480
   ? kasan_save_stack+0x33/0x60
   ? kasan_set_track+0x25/0x30
   ? ____kasan_slab_free+0x126/0x170
   smb2_queryfs+0xc2/0x2c0 [cifs]
   ? __pfx_smb2_queryfs+0x10/0x10 [cifs]
   ? __pfx___lock_acquire+0x10/0x10
   smb311_queryfs+0x210/0x220 [cifs]
   ? __pfx_smb311_queryfs+0x10/0x10 [cifs]
   ? srso_alias_return_thunk+0x5/0x7f
   ? __lock_acquire+0x480/0x26c0
   ? lock_release+0x1ed/0x640
   ? srso_alias_return_thunk+0x5/0x7f
   ? do_raw_spin_unlock+0x9b/0x100
   cifs_statfs+0x18c/0x4b0 [cifs]
   statfs_by_dentry+0x9b/0xf0
   fd_statfs+0x4e/0xb0
   __do_sys_fstatfs+0x7f/0xe0
   ? __pfx___do_sys_fstatfs+0x10/0x10
   ? srso_alias_return_thunk+0x5/0x7f
   ? lockdep_hardirqs_on_prepare+0x136/0x200
   ? srso_alias_return_thunk+0x5/0x7f
   do_syscall_64+0x3f/0x90
   entry_SYSCALL_64_after_hwframe+0x6e/0xd8

  Allocated by task 27534:
   kasan_save_stack+0x33/0x60
   kasan_set_track+0x25/0x30
   __kasan_kmalloc+0x8f/0xa0
   open_cached_dir+0x71b/0x1240 [cifs]
   smb2_query_info_compound+0x5c3/0x6d0 [cifs]
   smb2_queryfs+0xc2/0x2c0 [cifs]
   smb311_queryfs+0x210/0x220 [cifs]
   cifs_statfs+0x18c/0x4b0 [cifs]
   statfs_by_dentry+0x9b/0xf0
   fd_statfs+0x4e/0xb0
   __do_sys_fstatfs+0x7f/0xe0
   do_syscall_64+0x3f/0x90
   entry_SYSCALL_64_after_hwframe+0x6e/0xd8

  Freed by task 27534:
   kasan_save_stack+0x33/0x60
   kasan_set_track+0x25/0x30
   kasan_save_free_info+0x2b/0x50
   ____kasan_slab_free+0x126/0x170
   slab_free_freelist_hook+0xd0/0x1e0
   __kmem_cache_free+0x9d/0x1b0
   open_cached_dir+0xff5/0x1240 [cifs]
   smb2_query_info_compound+0x5c3/0x6d0 [cifs]
   smb2_queryfs+0xc2/0x2c0 [cifs]

This is a race between open_cached_dir() and cached_dir_lease_break() where the cache entry for the open directory handle receives a lease break while creating it. And before returning from open_cached_dir(), we put the last reference of the new @cfid because of !@cfid->has_lease.

Besides the UAF, while running xfstests a lot of missed lease breaks have been noticed in tests that run several concurrent statfs(2) calls on those cached fids

CIFS: VFS: \\w22-root1.gandalf.test No task to wake, unknown frame...
CIFS: VFS: \\w22-root1.gandalf.test Cmd: 18 Err: 0x0 Flags: 0x1...
CIFS: VFS: \\w22-root1.gandalf.test smb buf 00000000715bfe83 len 108
CIFS: VFS: Dump pending requests:
CIFS: VFS: \\w22-root1.gandalf.test No task to wake, unknown frame...
CIFS: VFS: \\w22-root1.gandalf.test Cmd: 18 Err: 0x0 Flags: 0x1...
CIFS: VFS: \\w22-root1.gandalf.test smb buf 000000005aa7316e len 108
...

To fix both, in open_cached_dir() ensure that @cfid->has_lease is set right before sending out compounded request so that any potential lease break will be get processed by demultiplex thread while we're still caching @cfid. And, if open failed for some reason, re-check @cfid->has_lease to decide whether or not put lease reference.

index fe1bf5b6e0cb..59f6b8e32cc9 100644
@@ -32,7 +32,7 @@ static struct cached_fid *find_or_create_cached_dir(struct cached_fids *cfids,
 			 * fully cached or it may be in the process of
 			 * being deleted due to a lease break.
 			 */
-			if (!cfid->has_lease) {
+			if (!cfid->time || !cfid->has_lease) {
 				spin_unlock(&cfids->cfid_list_lock);
 				return NULL;
 			}

@@ -193,10 +193,20 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 	npath = path_no_prefix(cifs_sb, path);
 	if (IS_ERR(npath)) {
 		rc = PTR_ERR(npath);
-		kfree(utf16_path);
-		return rc;
+		goto out;
 	}
 
+	if (!npath[0]) {
+		dentry = dget(cifs_sb->root);
+	} else {
+		dentry = path_to_dentry(cifs_sb, npath);
+		if (IS_ERR(dentry)) {
+			rc = -ENOENT;
+			goto out;
+		}
+	}
+	cfid->dentry = dentry;
+
 	/*
 	 * We do not hold the lock for the open because in case
 	 * SMB2_open needs to reconnect.

@@ -249,6 +259,15 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 
 	smb2_set_related(&rqst[1]);
 
+	/*
+	 * Set @cfid->has_lease to true before sending out compounded request so
+	 * its lease reference can be put in cached_dir_lease_break() due to a
+	 * potential lease break right after the request is sent or while @cfid
+	 * is still being cached.  Concurrent processes won't be to use it yet
+	 * due to @cfid->time being zero.
+	 */
+	cfid->has_lease = true;
+
 	rc = compound_send_recv(xid, ses, server,
 				flags, 2, rqst,
 				resp_buftype, rsp_iov);

@@ -263,6 +282,8 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 	cfid->tcon = tcon;
 	cfid->is_open = true;
 
+	spin_lock(&cfids->cfid_list_lock);
+
 	o_rsp = (struct smb2_create_rsp *)rsp_iov[0].iov_base;
 	oparms.fid->persistent_fid = o_rsp->PersistentFileId;
 	oparms.fid->volatile_fid = o_rsp->VolatileFileId;

@@ -270,18 +291,25 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 	oparms.fid->mid = le64_to_cpu(o_rsp->hdr.MessageId);
 #endif /* CIFS_DEBUG2 */
 
-	if (o_rsp->OplockLevel != SMB2_OPLOCK_LEVEL_LEASE)
+	rc = -EINVAL;
+	if (o_rsp->OplockLevel != SMB2_OPLOCK_LEVEL_LEASE) {
+		spin_unlock(&cfids->cfid_list_lock);
 		goto oshr_free;
+	}
 
 	smb2_parse_contexts(server, o_rsp,
 			    &oparms.fid->epoch,
 			    oparms.fid->lease_key, &oplock,
 			    NULL, NULL);
-	if (!(oplock & SMB2_LEASE_READ_CACHING_HE))
+	if (!(oplock & SMB2_LEASE_READ_CACHING_HE)) {
+		spin_unlock(&cfids->cfid_list_lock);
 		goto oshr_free;
+	}
 	qi_rsp = (struct smb2_query_info_rsp *)rsp_iov[1].iov_base;
-	if (le32_to_cpu(qi_rsp->OutputBufferLength) < sizeof(struct smb2_file_all_info))
+	if (le32_to_cpu(qi_rsp->OutputBufferLength) < sizeof(struct smb2_file_all_info)) {
+		spin_unlock(&cfids->cfid_list_lock);
 		goto oshr_free;
+	}
 	if (!smb2_validate_and_copy_iov(
 				le16_to_cpu(qi_rsp->OutputBufferOffset),
 				sizeof(struct smb2_file_all_info),

@@ -289,37 +317,24 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 				(char *)&cfid->file_all_info))
 		cfid->file_all_info_is_valid = true;
 
-	if (!npath[0])
-		dentry = dget(cifs_sb->root);
-	else {
-		dentry = path_to_dentry(cifs_sb, npath);
-		if (IS_ERR(dentry)) {
-			rc = -ENOENT;
-			goto oshr_free;
-		}
-	}
-	spin_lock(&cfids->cfid_list_lock);
-	cfid->dentry = dentry;
 	cfid->time = jiffies;
-	cfid->has_lease = true;
 	spin_unlock(&cfids->cfid_list_lock);
+	/* At this point the directory handle is fully cached */
+	rc = 0;
 
 oshr_free:
-	kfree(utf16_path);
 	SMB2_open_free(&rqst[0]);
 	SMB2_query_info_free(&rqst[1]);
 	free_rsp_buf(resp_buftype[0], rsp_iov[0].iov_base);
 	free_rsp_buf(resp_buftype[1], rsp_iov[1].iov_base);
-	spin_lock(&cfids->cfid_list_lock);
-	if (!cfid->has_lease) {
-		if (rc) {
-			if (cfid->on_list) {
-				list_del(&cfid->entry);
-				cfid->on_list = false;
-				cfids->num_entries--;
-			}
-			rc = -ENOENT;
-		} else {
+	if (rc) {
+		spin_lock(&cfids->cfid_list_lock);
+		if (cfid->on_list) {
+			list_del(&cfid->entry);
+			cfid->on_list = false;
+			cfids->num_entries--;
+		}
+		if (cfid->has_lease) {
 			/*
 			 * We are guaranteed to have two references at this
 			 * point. One for the caller and one for a potential

@@ -327,25 +342,24 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 			 * will be closed when the caller closes the cached
 			 * handle.
 			 */
+			cfid->has_lease = false;
 			spin_unlock(&cfids->cfid_list_lock);
 			kref_put(&cfid->refcount, smb2_close_cached_fid);
 			goto out;
 		}
+		spin_unlock(&cfids->cfid_list_lock);
 	}
-	spin_unlock(&cfids->cfid_list_lock);
+out:
 	if (rc) {
 		if (cfid->is_open)
 			SMB2_close(0, cfid->tcon, cfid->fid.persistent_fid,
 				   cfid->fid.volatile_fid);
 		free_cached_dir(cfid);
-		cfid = NULL;
-	}
-out:
-	if (rc == 0) {
+	} else {
 		*ret_cfid = cfid;
 		atomic_inc(&tcon->num_remote_opens);
 	}
-
+	kfree(utf16_path);
 	return rc;
 }