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smb: client: fix potential UAF in smb2_close_cached_fid()

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find_or_create_cached_dir() could grab a new reference after kref_put()
had seen the refcount drop to zero but before cfid_list_lock is acquired
in smb2_close_cached_fid(), leading to use-after-free.

Switch to kref_put_lock() so cfid_release() is called with
cfid_list_lock held, closing that gap.

Fixes: ebe98f1447 ("cifs: enable caching of directories for which a lease is held")
Cc: stable@vger.kernel.org
Reported-by: Jay Shin <jaeshin@redhat.com>
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Signed-off-by: Henrique Carvalho <henrique.carvalho@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Henrique Carvalho 2025-11-03 19:52:55 -03:00 committed by Steve French
parent 6146a0f1df
commit 734e99623c
1 changed files with 9 additions and 7 deletions
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16
fs/smb/client/cached_dir.c
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@ -388,11 +388,11 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
* lease. Release one here, and the second below.
*/
cfid->has_lease = false;
kref_put(&cfid->refcount, smb2_close_cached_fid);
close_cached_dir(cfid);
}
spin_unlock(&cfids->cfid_list_lock);
kref_put(&cfid->refcount, smb2_close_cached_fid);
close_cached_dir(cfid);
} else {
*ret_cfid = cfid;
atomic_inc(&tcon->num_remote_opens);
@ -438,12 +438,14 @@ int open_cached_dir_by_dentry(struct cifs_tcon *tcon,
static void
smb2_close_cached_fid(struct kref *ref)
__releases(&cfid->cfids->cfid_list_lock)
{
struct cached_fid *cfid = container_of(ref, struct cached_fid,
refcount);
int rc;
spin_lock(&cfid->cfids->cfid_list_lock);
lockdep_assert_held(&cfid->cfids->cfid_list_lock);
if (cfid->on_list) {
list_del(&cfid->entry);
cfid->on_list = false;
@ -478,7 +480,7 @@ void drop_cached_dir_by_name(const unsigned int xid, struct cifs_tcon *tcon,
spin_lock(&cfid->cfids->cfid_list_lock);
if (cfid->has_lease) {
cfid->has_lease = false;
kref_put(&cfid->refcount, smb2_close_cached_fid);
close_cached_dir(cfid);
}
spin_unlock(&cfid->cfids->cfid_list_lock);
close_cached_dir(cfid);
@ -487,7 +489,7 @@ void drop_cached_dir_by_name(const unsigned int xid, struct cifs_tcon *tcon,
void close_cached_dir(struct cached_fid *cfid)
{
kref_put(&cfid->refcount, smb2_close_cached_fid);
kref_put_lock(&cfid->refcount, smb2_close_cached_fid, &cfid->cfids->cfid_list_lock);
}
/*
@ -596,7 +598,7 @@ cached_dir_offload_close(struct work_struct *work)
WARN_ON(cfid->on_list);
kref_put(&cfid->refcount, smb2_close_cached_fid);
close_cached_dir(cfid);
cifs_put_tcon(tcon, netfs_trace_tcon_ref_put_cached_close);
}
@ -762,7 +764,7 @@ static void cfids_laundromat_worker(struct work_struct *work)
* 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);
close_cached_dir(cfid);
}
queue_delayed_work(cfid_put_wq, &cfids->laundromat_work,
dir_cache_timeout * HZ);