linux-kernel - Re: WARNING: CPU: 1 PID: 14735 at fs/dcache.c:365 dentry

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Date:   Wed, 20 Jul 2022 03:31:10 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Helge Deller <deller@....de>
Cc:     Hillf Danton <hdanton@...a.com>, linux-kernel@...r.kernel.org,
        linux-parisc@...r.kernel.org
Subject: Re: WARNING: CPU: 1 PID: 14735 at fs/dcache.c:365
 dentry_free+0x100/0x128

On Sat, Jul 16, 2022 at 07:27:30AM +0200, Helge Deller wrote:
> [108564.845444] dentry = 000000031624e6c0

*blink*
Is that really a plausible address of a kernel object on
parisc?  Or is that "mangle pointers for security fetish^W
purposes, lest somebody manages to get a useful information
out of dmesg" in action?

> [108564.889437] spin_is_locked(&dentry->d_lock) = 0
> [108564.945436] dname_external(dentry) = 0
> [108564.993436] dentry->d_flags & DCACHE_NORCU = 0
> [108565.045446] dentry->d_name.len = 3
> [108565.089435] dentry->d_name.hash = 89116695
> [108565.137435] dentry->d_lockref.count = -128
> [108565.189434] dentry->d_flags = 32776

0x8008, i.e. DCACHE_OP_DELETE | DCACHE_DENTRY_KILLED.  No
DCACHE_PAR_LOOKUP in sight...

> [108569.801407] dentry = 000000016d7d0000
> [108569.845407] spin_is_locked(&dentry->d_lock) = 0
> [108569.901422] dname_external(dentry) = 0
> [108569.949405] dentry->d_flags & DCACHE_NORCU = 0
> [108570.001405] dentry->d_name.len = 10
> [108570.045421] dentry->d_name.hash = e6582e53
> [108570.093476] dentry->d_lockref.count = -128
> [108570.145404] dentry->d_flags = 32776
> [108570.189420] dentry->d_inode = 0000000000000000
> [108570.241404] dentry->d_parent = 00000002332c2780
> [108570.297403] dentry->d_u.d_rcu = 0x416be770

Ditto.  Pointers look really weird...