added Cc: stable and tentatively merged this to for-next
On Mon, Oct 30, 2023 at 3:20 PM Paulo Alcantara <pc@xxxxxxxxxxxxx> wrote:
>
> 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.
>
> Signed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxxxxxxxxx>
> ---
> fs/smb/client/cached_dir.c | 84 ++++++++++++++++++++++----------------
> 1 file changed, 49 insertions(+), 35 deletions(-)
>
> diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
> index fe1bf5b6e0cb..59f6b8e32cc9 100644
> --- a/fs/smb/client/cached_dir.c
> +++ b/fs/smb/client/cached_dir.c
> @@ -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;
> }
>
> --
> 2.42.0
>
--
Thanks,
Steve
