linux-kernel - Re: [PATCH -next] Revert "evm: Fix memleak in init

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Message-ID: <5842536c5c2bde1e3c2840f7e877becc3282b47c.camel@linux.ibm.com>
Date:   Fri, 10 Jun 2022 10:20:15 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Xiu Jianfeng <xiujianfeng@...wei.com>, dmitry.kasatkin@...il.com,
        jmorris@...ei.org, serge@...lyn.com,
        "Guozihua (Scott)" <guozihua@...wei.com>
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] Revert "evm: Fix memleak in init_desc"

On Fri, 2022-05-27 at 19:17 +0800, Xiu Jianfeng wrote:
> This reverts commit ccf11dbaa07b328fa469415c362d33459c140a37.
> 
> Commit ccf11dbaa07b ("evm: Fix memleak in init_desc") said there is
> memleak in init_desc. That may be incorrect, as we can see, tmp_tfm is
> saved in one of the two global variables hmac_tfm ohr evm_tfm[hash_algo],
> then if init_desc is called next time, there is no need to alloc tfm
> again, so in the error path of kmalloc desc or crypto_shash_init(desc),
> It is not a problem without freeing tmp_tfm.
> 
> And also that commit did not reset the global variable to NULL after
> freeing tmp_tfm and this makes *tfm a dangling pointer which may cause a
> UAF issue.
> 
> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>

Agreed, thanks.  This was first reported by Guozihua (Scott) <
guozihua@...wei.com>.  If neither you nor Scott object, I'll add his
Reported-by tag.

thanks,

Mimi