6.6-stable review patch. If anyone has any objections, please let me know.
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From: Paulo Alcantara pc@manguebit.com
commit 5c86919455c1edec99ebd3338ad213b59271a71b upstream.
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.
Cc: stable@vger.kernel.org Signed-off-by: Paulo Alcantara (SUSE) pc@manguebit.com Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/smb/client/cached_dir.c | 84 ++++++++++++++++++++++++++------------------- 1 file changed, 49 insertions(+), 35 deletions(-)
--- 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 * 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, st 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, st
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, st 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, st 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, st (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 @@ oshr_free: * 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; }