2023-10-13 2:43 GMT+09:00, Marios Makassikis <mmakassikis@xxxxxxxxxx>:
> 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
>
> stack backtrace:
> CPU: 1 PID: 32 Comm: kworker/1:1 Not tainted 6.6.0-rc5 #775
> Workqueue: ksmbd-io handle_ksmbd_work
> Call Trace:
> <TASK>
> dump_stack_lvl+0x4f/0x90
> dump_stack+0x14/0x20
> print_deadlock_bug+0x2f0/0x410
> check_deadlock+0x26b/0x3b0
> __lock_acquire+0xce2/0x1060
> ? mark_lock.part.0+0xff/0x720
> ? __pfx___lock_acquire+0x10/0x10
> ? mark_held_locks+0x6b/0x90
> lock_acquire.part.0+0x125/0x2d0
> ? ksmbd_vfs_mkdir+0xe1/0x410
> ? __pfx_lock_acquire.part.0+0x10/0x10
> ? __kmem_cache_free+0x179/0x280
> ? ____kasan_slab_free+0x15b/0x1d0
> ? __kasan_slab_free+0x16/0x20
> ? slab_free_freelist_hook+0xbc/0x180
> lock_acquire+0x93/0x160
> ? ksmbd_vfs_mkdir+0xe1/0x410
> mnt_want_write+0x49/0x220
> ? ksmbd_vfs_mkdir+0xe1/0x410
> ksmbd_vfs_mkdir+0xe1/0x410
> ? __pfx__printk+0x10/0x10
> ? __pfx_ksmbd_vfs_mkdir+0x10/0x10
> smb2_open+0x1064/0x38b0
> ? __pfx___lock_acquire+0x10/0x10
> ? __pfx_smb2_open+0x10/0x10
> ? __lock_release+0x13f/0x290
> ? smb2_validate_credit_charge+0x25d/0x360
> ? __pfx___lock_release+0x10/0x10
> ? do_raw_spin_lock+0x127/0x1c0
> ? __pfx_do_raw_spin_lock+0x10/0x10
> ? do_raw_spin_unlock+0xac/0x110
> ? _raw_spin_unlock+0x22/0x50
> ? smb2_validate_credit_charge+0x25d/0x360
> ? ksmbd_smb2_check_message+0x3be/0x400
> ? __pfx_ksmbd_smb2_check_message+0x10/0x10
> __process_request+0x151/0x310
> __handle_ksmbd_work+0x33c/0x520
> ? __pfx___handle_ksmbd_work+0x10/0x10
> handle_ksmbd_work+0x4a/0xd0
> process_one_work+0x4a7/0x980
> ? __pfx_process_one_work+0x10/0x10
> ? assign_work+0xe1/0x120
> worker_thread+0x365/0x570
> ? __pfx_worker_thread+0x10/0x10
> kthread+0x18d/0x1d0
> ? __pfx_kthread+0x10/0x10
> ret_from_fork+0x38/0x70
> ? __pfx_kthread+0x10/0x10
> ret_from_fork_asm+0x1b/0x30
> </TASK>
>
> Fixes: 40b268d384a2 ("ksmbd: add mnt_want_write to ksmbd vfs functions")
> Signed-off-by: Marios Makassikis <mmakassikis@xxxxxxxxxx>
> ---
> fs/smb/server/vfs.c | 17 -----------------
> 1 file changed, 17 deletions(-)
>
> diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c
> index b5a5e50fc9ca..ac49e295d4c3 100644
> --- a/fs/smb/server/vfs.c
> +++ b/fs/smb/server/vfs.c
> @@ -173,10 +173,6 @@ 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_idmap(path.mnt), d_inode(path.dentry),
> dentry, mode, true);
> @@ -186,9 +182,7 @@ 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;
> }
> @@ -219,10 +213,6 @@ 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;
> -
> idmap = mnt_idmap(path.mnt);
> mode |= S_IFDIR;
> err = vfs_mkdir(idmap, d_inode(path.dentry), dentry, mode);
> @@ -246,8 +236,6 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char
> *name, umode_t mode)
> }
>
> out_err1:
minor nit: we can change it with our_err if removing out_err2.
> - mnt_drop_write(path.mnt);
> -out_err2:
> done_path_create(&path, dentry);
> if (err)
> pr_err("mkdir(%s): creation failed (err:%d)\n", name, err);
> @@ -665,16 +653,11 @@ 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_idmap(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);
> --
> 2.34.1
>
>
