| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <Z9uGCaxYJgs1gvwM@vaarsuvius.home.arpa>
Date: Wed, 19 Mar 2025 20:05:45 -0700
From: Paul Aurich <paul@...krain42.org>
To: Cliff Liu <donghua.liu@...driver.com>
Cc: stable@...r.kernel.org, sfrench@...ba.org, pc@....nz,
lsahlber@...hat.com, sprasad@...rosoft.com, tom@...pey.com,
linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
linux-kernel@...r.kernel.org, Zhe.He@...driver.com
Subject: Re: [PATCH 6.1.y] smb: prevent use-after-free due to open_cached_dir
error paths
Thanks for backporting this! I think you should pick up these patches as
pre-requisites for the one here:
- 5c86919455c1 ("smb: client: fix use-after-free in
smb2_query_info_compound()")
- 7afb86733685 ("smb: Don't leak cfid when reconnect races with
open_cached_dir")
All three of these patches touch on how the cached directory handling of the
'has_lease' field works, and my work was built on top of those.
On 2025-03-19 17:08:39 +0800, Cliff Liu wrote:
>From: Paul Aurich <paul@...krain42.org>
>
>If open_cached_dir() encounters an error parsing the lease from the
>server, the error handling may race with receiving a lease break,
>resulting in open_cached_dir() freeing the cfid while the queued work is
>pending.
>
>Update open_cached_dir() to drop refs rather than directly freeing the
>cfid.
>
>Have cached_dir_lease_break(), cfids_laundromat_worker(), and
>invalidate_all_cached_dirs() clear has_lease immediately while still
>holding cfids->cfid_list_lock, and then use this to also simplify the
>reference counting in cfids_laundromat_worker() and
>invalidate_all_cached_dirs().
>
>Fixes this KASAN splat (which manually injects an error and lease break
>in open_cached_dir()):
>
>==================================================================
>BUG: KASAN: slab-use-after-free in smb2_cached_lease_break+0x27/0xb0
>Read of size 8 at addr ffff88811cc24c10 by task kworker/3:1/65
>
>CPU: 3 UID: 0 PID: 65 Comm: kworker/3:1 Not tainted 6.12.0-rc6-g255cf264e6e5-dirty #87
>Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
>Workqueue: cifsiod smb2_cached_lease_break
>Call Trace:
> <TASK>
> dump_stack_lvl+0x77/0xb0
> print_report+0xce/0x660
> kasan_report+0xd3/0x110
> smb2_cached_lease_break+0x27/0xb0
> process_one_work+0x50a/0xc50
> worker_thread+0x2ba/0x530
> kthread+0x17c/0x1c0
> ret_from_fork+0x34/0x60
> ret_from_fork_asm+0x1a/0x30
> </TASK>
>
>Allocated by task 2464:
> kasan_save_stack+0x33/0x60
> kasan_save_track+0x14/0x30
> __kasan_kmalloc+0xaa/0xb0
> open_cached_dir+0xa7d/0x1fb0
> smb2_query_path_info+0x43c/0x6e0
> cifs_get_fattr+0x346/0xf10
> cifs_get_inode_info+0x157/0x210
> cifs_revalidate_dentry_attr+0x2d1/0x460
> cifs_getattr+0x173/0x470
> vfs_statx_path+0x10f/0x160
> vfs_statx+0xe9/0x150
> vfs_fstatat+0x5e/0xc0
> __do_sys_newfstatat+0x91/0xf0
> do_syscall_64+0x95/0x1a0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
>Freed by task 2464:
> kasan_save_stack+0x33/0x60
> kasan_save_track+0x14/0x30
> kasan_save_free_info+0x3b/0x60
> __kasan_slab_free+0x51/0x70
> kfree+0x174/0x520
> open_cached_dir+0x97f/0x1fb0
> smb2_query_path_info+0x43c/0x6e0
> cifs_get_fattr+0x346/0xf10
> cifs_get_inode_info+0x157/0x210
> cifs_revalidate_dentry_attr+0x2d1/0x460
> cifs_getattr+0x173/0x470
> vfs_statx_path+0x10f/0x160
> vfs_statx+0xe9/0x150
> vfs_fstatat+0x5e/0xc0
> __do_sys_newfstatat+0x91/0xf0
> do_syscall_64+0x95/0x1a0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
>Last potentially related work creation:
> kasan_save_stack+0x33/0x60
> __kasan_record_aux_stack+0xad/0xc0
> insert_work+0x32/0x100
> __queue_work+0x5c9/0x870
> queue_work_on+0x82/0x90
> open_cached_dir+0x1369/0x1fb0
> smb2_query_path_info+0x43c/0x6e0
> cifs_get_fattr+0x346/0xf10
> cifs_get_inode_info+0x157/0x210
> cifs_revalidate_dentry_attr+0x2d1/0x460
> cifs_getattr+0x173/0x470
> vfs_statx_path+0x10f/0x160
> vfs_statx+0xe9/0x150
> vfs_fstatat+0x5e/0xc0
> __do_sys_newfstatat+0x91/0xf0
> do_syscall_64+0x95/0x1a0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
>The buggy address belongs to the object at ffff88811cc24c00
> which belongs to the cache kmalloc-1k of size 1024
>The buggy address is located 16 bytes inside of
> freed 1024-byte region [ffff88811cc24c00, ffff88811cc25000)
>
>Cc: stable@...r.kernel.org
>Signed-off-by: Paul Aurich <paul@...krain42.org>
>Signed-off-by: Steve French <stfrench@...rosoft.com>
>[ Do not apply the change for cfids_laundromat_worker() since there is no
> this function and related feature on 6.1.y. Update open_cached_dir()
> according to method of upstream patch. ]
>Signed-off-by: Cliff Liu <donghua.liu@...driver.com>
>Signed-off-by: He Zhe <Zhe.He@...driver.com>
>---
>Verified the build test.
>---
> fs/smb/client/cached_dir.c | 39 ++++++++++++++++----------------------
> 1 file changed, 16 insertions(+), 23 deletions(-)
>
>diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
>index d09226c1ac90..d65d5fe5b8fe 100644
>--- a/fs/smb/client/cached_dir.c
>+++ b/fs/smb/client/cached_dir.c
>@@ -320,17 +320,13 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
> /*
> * We are guaranteed to have two references at this point.
> * One for the caller and one for a potential lease.
>- * Release the Lease-ref so that the directory will be closed
>- * when the caller closes the cached handle.
>+ * Release one here, and the second below.
> */
> kref_put(&cfid->refcount, smb2_close_cached_fid);
> }
> 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;
>+ cfid->has_lease = false;
This should be cleared while holding cfids->cfid_list_lock, which is what the
upstream version of this backport (a9685b409a0) does, because of how this
error handling was adjusted in 5c86919455c1 ("smb: client: fix use-after-free
in smb2_query_info_compound()")
>+ kref_put(&cfid->refcount, smb2_close_cached_fid);
> }
>
> if (rc == 0) {
>@@ -462,25 +458,24 @@ void invalidate_all_cached_dirs(struct cifs_tcon *tcon)
> cfids->num_entries--;
> cfid->is_open = false;
> cfid->on_list = false;
>- /* To prevent race with smb2_cached_lease_break() */
>- kref_get(&cfid->refcount);
>+ if (cfid->has_lease) {
>+ /*
>+ * The lease was never cancelled from the server,
>+ * so steal that reference.
>+ */
>+ cfid->has_lease = false;
>+ } else
>+ kref_get(&cfid->refcount);
> }
> spin_unlock(&cfids->cfid_list_lock);
>
> list_for_each_entry_safe(cfid, q, &entry, entry) {
> list_del(&cfid->entry);
> cancel_work_sync(&cfid->lease_break);
>- if (cfid->has_lease) {
>- /*
>- * We lease was never cancelled from the server so we
>- * need to drop the reference.
>- */
>- spin_lock(&cfids->cfid_list_lock);
>- cfid->has_lease = false;
>- spin_unlock(&cfids->cfid_list_lock);
>- kref_put(&cfid->refcount, smb2_close_cached_fid);
>- }
>- /* Drop the extra reference opened above*/
>+ /*
>+ * Drop the ref-count from above, either the lease-ref (if there
>+ * was one) or the extra one acquired.
>+ */
> kref_put(&cfid->refcount, smb2_close_cached_fid);
> }
> }
>@@ -491,9 +486,6 @@ smb2_cached_lease_break(struct work_struct *work)
> struct cached_fid *cfid = container_of(work,
> struct cached_fid, lease_break);
>
>- spin_lock(&cfid->cfids->cfid_list_lock);
>- cfid->has_lease = false;
>- spin_unlock(&cfid->cfids->cfid_list_lock);
> kref_put(&cfid->refcount, smb2_close_cached_fid);
> }
>
>@@ -511,6 +503,7 @@ int cached_dir_lease_break(struct cifs_tcon *tcon, __u8 lease_key[16])
> !memcmp(lease_key,
> cfid->fid.lease_key,
> SMB2_LEASE_KEY_SIZE)) {
>+ cfid->has_lease = false;
> cfid->time = 0;
> /*
> * We found a lease remove it from the list
>--
>2.43.0
>
~Paul
Powered by blists - more mailing lists