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ksmbd: fix recursive locking in vfs helpers

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[ Upstream commit 807252f028c59b9a3bac4d62ad84761548c10f11 ]

Running smb2.rename test from Samba smbtorture suite against a kernel built
with lockdep triggers a "possible recursive locking detected" warning.

This is because mnt_want_write() is called twice with no mnt_drop_write()
in between:
  -> ksmbd_vfs_mkdir()
    -> ksmbd_vfs_kern_path_create()
       -> kern_path_create()
          -> filename_create()
            -> mnt_want_write()
       -> mnt_want_write()

Fix this by removing the mnt_want_write/mnt_drop_write calls from vfs
helpers that call kern_path_create().

Full lockdep trace below:

============================================
WARNING: possible recursive locking detected
6.6.0-rc5 #775 Not tainted
--------------------------------------------
kworker/1:1/32 is trying to acquire lock:
ffff888005ac83f8 (sb_writers#5){.+.+}-{0:0}, at: ksmbd_vfs_mkdir+0xe1/0x410

but task is already holding lock:
ffff888005ac83f8 (sb_writers#5){.+.+}-{0:0}, at: filename_create+0xb6/0x260

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(sb_writers#5);
  lock(sb_writers#5);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by kworker/1:1/32:
 #0: ffff8880064e4138 ((wq_completion)ksmbd-io){+.+.}-{0:0}, at: process_one_work+0x40e/0x980
 #1: ffff888005b0fdd0 ((work_completion)(&work->work)){+.+.}-{0:0}, at: process_one_work+0x40e/0x980
 #2: ffff888005ac83f8 (sb_writers#5){.+.+}-{0:0}, at: filename_create+0xb6/0x260
 #3: ffff8880057ce760 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: filename_create+0x123/0x260

Cc: stable@vger.kernel.org
Fixes: 40b268d384a2 ("ksmbd: add mnt_want_write to ksmbd vfs functions")
Signed-off-by: Marios Makassikis <mmakassikis@freebox.fr>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Marios Makassikis 2023-12-31 16:13:14 +09:00 • committed by Greg Kroah-Hartman
parent 42e56982be
commit 5113f72225
1 changed files with 3 additions and 20 deletions
Download patch file Download diff file Expand all files Collapse all files

23
fs/smb/server/vfs.c
View file

@ -174,10 +174,6 @@ int ksmbd_vfs_create(struct ksmbd_work *work, const char *name, umode_t mode)
return err;
}
err = mnt_want_write(path.mnt);
if (err)
goto out_err;
mode |= S_IFREG;
err = vfs_create(mnt_user_ns(path.mnt), d_inode(path.dentry),
dentry, mode, true);
@ -187,9 +183,7 @@ int ksmbd_vfs_create(struct ksmbd_work *work, const char *name, umode_t mode)
} else {
pr_err("File(%s): creation failed (err:%d)\n", name, err);
}
mnt_drop_write(path.mnt);
out_err:
done_path_create(&path, dentry);
return err;
}
@ -220,10 +214,6 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
return err;
}
err = mnt_want_write(path.mnt);
if (err)
goto out_err2;
user_ns = mnt_user_ns(path.mnt);
mode |= S_IFDIR;
err = vfs_mkdir(user_ns, d_inode(path.dentry), dentry, mode);
@ -234,21 +224,19 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
dentry->d_name.len);
if (IS_ERR(d)) {
err = PTR_ERR(d);
goto out_err1;
goto out_err;
}
if (unlikely(d_is_negative(d))) {
dput(d);
err = -ENOENT;
goto out_err1;
goto out_err;
}
ksmbd_vfs_inherit_owner(work, d_inode(path.dentry), d_inode(d));
dput(d);
}
out_err1:
mnt_drop_write(path.mnt);
out_err2:
out_err:
done_path_create(&path, dentry);
if (err)
pr_err("mkdir(%s): creation failed (err:%d)\n", name, err);
@ -666,16 +654,11 @@ int ksmbd_vfs_link(struct ksmbd_work *work, const char *oldname,
goto out3;
}
err = mnt_want_write(newpath.mnt);
if (err)
goto out3;
err = vfs_link(oldpath.dentry, mnt_user_ns(newpath.mnt),
d_inode(newpath.dentry),
dentry, NULL);
if (err)
ksmbd_debug(VFS, "vfs_link failed err %d\n", err);
mnt_drop_write(newpath.mnt);
out3:
done_path_create(&newpath, dentry);