linux-kernel - Re: [PATCH v2 2/3] IMA: Add log statements for failure conditions.

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Message-ID: <5c6098c369de85abc5273fdda5da4e1dc5228dc9.camel@perches.com>
Date:   Tue, 11 Feb 2020 12:09:50 -0800
From:   Joe Perches <joe@...ches.com>
To:     Tushar Sugandhi <tusharsu@...ux.microsoft.com>,
        zohar@...ux.ibm.com, skhan@...uxfoundation.org,
        linux-integrity@...r.kernel.org
Cc:     sashal@...nel.org, nramas@...ux.microsoft.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] IMA: Add log statements for failure conditions.

On Tue, 2020-02-11 at 11:14 -0800, Tushar Sugandhi wrote:
> Hi Joe,

Rehi Tushar.

> On 2020-02-10 7:23 p.m., Joe Perches wrote:
> > On Mon, 2020-02-10 at 18:47 -0800, Tushar Sugandhi wrote:
> > > process_buffer_measurement() and ima_alloc_key_entry()
> > > functions do not have log messages for failure conditions.
[]
> > > diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
> > []
> > > @@ -90,6 +90,7 @@ static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
> > >   
> > >   out:
> > >   	if (rc) {
> > > +		pr_err("Key entry allocation failed, result: %d\n", rc);
> > >   		ima_free_key_entry(entry);
> > >   		entry = NULL;
> > >   	}
> > 
> > Likely the pr_err is unnecessary here as kmalloc, kstrdup
> > and kmemdup all emit a dump_stack() on allocation failure.
> Thanks for pointing out kmalloc, kstrdup, and kmemdup emit a 
> dump_stack(). But keeping the above pr_err() will help associate the 
> failure with IMA.
> For instance - "dmesg | grep ima:" will include this error.
> Perhaps I should add __func__ here as well.
> And since we are redefining the pr_fmt to prefix module and base names, 
> it will help further to pinpoint where exactly the failure is coming from.

The dump_stack is preferred over a single printk message
and the association isn't particularly useful.

> Thanks again. This recommended change certainly makes the code more 
> readable. But again, I am not sure if this patchset is the right one for 
> this proposed change.
> Perhaps I can create another patchset for the above two recommended 
> changes, and only focus on improving logging in this patchset?

Your choice.