Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH 4.19 00/95] 4.19.209-rc1 review
To:     Eric Dumazet <edumazet@google.com>,
        Naresh Kamboju <naresh.kamboju@linaro.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        open list <linux-kernel@vger.kernel.org>,
        Shuah Khan <shuah@kernel.org>,
        Florian Fainelli <f.fainelli@gmail.com>, patches@kernelci.org,
        lkft-triage@lists.linaro.org, Jon Hunter <jonathanh@nvidia.com>,
        linux-stable <stable@vger.kernel.org>,
        Pavel Machek <pavel@denx.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Netdev <netdev@vger.kernel.org>, Jann Horn <jannh@google.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Luiz Augusto von Dentz <luiz.von.dentz@intel.com>,
        Marcel Holtmann <marcel@holtmann.org>,
        "David S. Miller" <davem@davemloft.net>,
        Shuah Khan <skhan@linuxfoundation.org>
References: <20211004125033.572932188@linuxfoundation.org>
 <CA+G9fYtyzfpSnapCFEVgeWGD8ZwS2_Lv5KPwjX4hUwDAv52kFg@mail.gmail.com>
 <CANn89iKPvyS1FB2z9XFr4Y1i8XXc34CTdbSAakjMC=NVYvwzXw@mail.gmail.com>
 <576d46b9-644f-ece0-2cf0-8abbe8b85f4a@linuxfoundation.org>
From:   Shuah Khan <skhan@linuxfoundation.org>
Message-ID: <14314f54-57fa-fa89-ce4c-ce79116d3d80@linuxfoundation.org>
Date:   Mon, 4 Oct 2021 14:34:50 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.8.1
MIME-Version: 1.0
In-Reply-To: <576d46b9-644f-ece0-2cf0-8abbe8b85f4a@linuxfoundation.org>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 10/4/21 1:49 PM, Shuah Khan wrote:
> On 10/4/21 11:44 AM, Eric Dumazet wrote:
>> On Mon, Oct 4, 2021 at 10:40 AM Naresh Kamboju
>> <naresh.kamboju@linaro.org> wrote:
>>>
>>> On Mon, 4 Oct 2021 at 18:32, Greg Kroah-Hartman
>>> <gregkh@linuxfoundation.org> wrote:
>>>>
>>>> This is the start of the stable review cycle for the 4.19.209 release.
>>>> There are 95 patches in this series, all will be posted as a response
>>>> to this one.  If anyone has any issues with these being applied, please
>>>> let me know.
>>>>
>>>> Responses should be made by Wed, 06 Oct 2021 12:50:17 +0000.
>>>> Anything received after that time might be too late.
>>>>
>>>> The whole patch series can be found in one patch at:
>>>>          https://www.kernel.org/pub/linux/kernel/v4.x/stable-review/patch-4.19.209-rc1.gz
>>>> or in the git tree and branch at:
>>>>          git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.19.y
>>>> and the diffstat can be found below.
>>>>
>>>> thanks,
>>>>
>>>> greg k-h
>>>
>>> Regression found on arm, arm64, i386 and x86.
>>> following kernel crash reported on stable-rc linux-4.19.y.
>>>
>>
>> Stable teams should backport cred: allow get_cred() and put_cred() to
>> be given NULL.
>>
>> f06bc03339ad4c1baa964a5f0606247ac1c3c50b
>>
>> Or they should have tweaked my patch before backporting it.
>>
> Seeing the same problem on my test system as well.
> 
> Patch applied with fuzz. Didn't need any tweaks. Compiling now.
> Will let you know soon.
> 

With f06bc03339ad4c1baa964a5f0606247ac1c3c50b

Compiled and booted on my test system. No dmesg regressions.

Tested-by: Shuah Khan <skhan@linuxfoundation.org>

-----------------------------------------------------------------------

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 1dc351d8548b..4b081e4911c8 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -240,7 +240,7 @@ static inline struct cred *get_new_cred(struct cred *cred)
   * @cred: The credentials to reference
   *
   * Get a reference on the specified set of credentials.  The caller must
- * release the reference.
+ * release the reference.  If %NULL is passed, it is returned with no action.
   *
   * This is used to deal with a committed set of credentials.  Although the
   * pointer is const, this will temporarily discard the const and increment the
@@ -251,6 +251,8 @@ static inline struct cred *get_new_cred(struct cred *cred)
  static inline const struct cred *get_cred(const struct cred *cred)
  {
         struct cred *nonconst_cred = (struct cred *) cred;
+       if (!cred)
+               return cred;
         validate_creds(cred);
         nonconst_cred->non_rcu = 0;
         return get_new_cred(nonconst_cred);
@@ -261,7 +263,7 @@ static inline const struct cred *get_cred(const struct cred *cred)
   * @cred: The credentials to release
   *
   * Release a reference to a set of credentials, deleting them when the last ref
- * is released.
+ * is released.  If %NULL is passed, nothing is done.
   *
   * This takes a const pointer to a set of credentials because the credentials
   * on task_struct are attached by const pointers to prevent accidental
@@ -271,9 +273,11 @@ static inline void put_cred(const struct cred *_cred)
  {
         struct cred *cred = (struct cred *) _cred;
  
-       validate_creds(cred);
-       if (atomic_dec_and_test(&(cred)->usage))
-               __put_cred(cred);
+       if (cred) {
+               validate_creds(cred);
+               if (atomic_dec_and_test(&(cred)->usage))
+                       __put_cred(cred);
+       }
  }
  
  /**

-----------------------------------------------------------------------

thanks,
-- Shuah