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:
- 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
