6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paulo Alcantara <pc@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Signed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;
}
