linux-kernel - Re: [RESEND][PATCH v3] security: Place security_path_post

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Date: Wed, 3 Apr 2024 23:21:50 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Roberto Sassu <roberto.sassu@...weicloud.com>
Cc: brauner@...nel.org, jack@...e.cz, paul@...l-moore.com,
	jmorris@...ei.org, serge@...lyn.com, zohar@...ux.ibm.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-cifs@...r.kernel.org,
	linux-integrity@...r.kernel.org, pc@...guebit.com,
	torvalds@...ux-foundation.org,
	Roberto Sassu <roberto.sassu@...wei.com>,
	Steve French <smfrench@...il.com>
Subject: Re: [RESEND][PATCH v3] security: Place security_path_post_mknod()
 where the original IMA call was

On Wed, Apr 03, 2024 at 11:07:49AM +0200, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.com>
> 
> Commit 08abce60d63f ("security: Introduce path_post_mknod hook")
> introduced security_path_post_mknod(), to replace the IMA-specific call to
> ima_post_path_mknod().
> 
> For symmetry with security_path_mknod(), security_path_post_mknod() was
> called after a successful mknod operation, for any file type, rather than
> only for regular files at the time there was the IMA call.
> 
> However, as reported by VFS maintainers, successful mknod operation does
> not mean that the dentry always has an inode attached to it (for example,
> not for FIFOs on a SAMBA mount).
> 
> If that condition happens, the kernel crashes when
> security_path_post_mknod() attempts to verify if the inode associated to
> the dentry is private.
> 
> Move security_path_post_mknod() where the ima_post_path_mknod() call was,
> which is obviously correct from IMA/EVM perspective. IMA/EVM are the only
> in-kernel users, and only need to inspect regular files.
> 
> Reported-by: Steve French <smfrench@...il.com>
> Closes: https://lore.kernel.org/linux-kernel/CAH2r5msAVzxCUHHG8VKrMPUKQHmBpE6K9_vjhgDa1uAvwx4ppw@mail.gmail.com/
> Suggested-by: Al Viro <viro@...iv.linux.org.uk>
> Fixes: 08abce60d63f ("security: Introduce path_post_mknod hook")
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>

LGTM...