linux-kernel - Re: [PATCH] fs/namei: fix WARNING in do

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Message-ID: <20250824190714.GG39973@ZenIV>
Date: Sun, 24 Aug 2025 20:07:14 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: ssranevjti@...il.com
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	brauner@...nel.org, jack@...e.cz,
	syzbot+0cee785b798102696a4b@...kaller.appspotmail.com,
	Shaurya Rane <ssrane_b23@...vjti.ac.in>
Subject: Re: [PATCH] fs/namei: fix WARNING in do_mknodat due to invalid inode
 unlock

On Mon, Aug 25, 2025 at 12:23:03AM +0530, ssranevjti@...il.com wrote:
> From: Shaurya Rane <ssrane_b23@...vjti.ac.in>
> 
> The done_path_create() function unconditionally calls inode_unlock() on
> path->dentry->d_inode without verifying that the path and inode are valid.
> Under certain error conditions or race scenarios, this can lead to attempting
> to unlock an inode that was never locked or has been corrupted, resulting in
> a WARNING from the rwsem debugging code.
> 
> Add defensive checks to ensure both path->dentry and path->dentry->d_inode
> are valid before attempting to unlock. This prevents the rwsem warning while
> maintaining existing behavior for normal cases.
> 
> Reported-by: syzbot+0cee785b798102696a4b@...kaller.appspotmail.com

No.  You are papering over some bugs you have not even bothered to describe -
"certain error conditions or race scenarios" is as useless as it gets.

Don't do that.  Fixing a bug found by syzbot is useful; papering over
it does no good whatsoever.

NAK.