linux-kernel - Re: [PATCH] KEYS: encrypted: Add check for strsep

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Message-Id: <CYS7OZUB3DQZ.5DGIZ3CKSM8G@suppilovahvero>
Date: Tue, 30 Jan 2024 19:20:18 +0200
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Jarkko Sakkinen" <jarkko@...nel.org>, "Verma, Vishal L"
 <vishal.l.verma@...el.com>, "zohar@...ux.ibm.com" <zohar@...ux.ibm.com>,
 "paul@...l-moore.com" <paul@...l-moore.com>, "dhowells@...hat.com"
 <dhowells@...hat.com>, "yaelt@...gle.com" <yaelt@...gle.com>,
 "serge@...lyn.com" <serge@...lyn.com>, "nichen@...as.ac.cn"
 <nichen@...as.ac.cn>, "sumit.garg@...aro.org" <sumit.garg@...aro.org>,
 "jmorris@...ei.org" <jmorris@...ei.org>
Cc: "Jiang, Dave" <dave.jiang@...el.com>, "linux-integrity@...r.kernel.org"
 <linux-integrity@...r.kernel.org>, "linux-cxl@...r.kernel.org"
 <linux-cxl@...r.kernel.org>, "linux-kernel@...r.kernel.org"
 <linux-kernel@...r.kernel.org>, "Williams, Dan J"
 <dan.j.williams@...el.com>, "keyrings@...r.kernel.org"
 <keyrings@...r.kernel.org>, "linux-security-module@...r.kernel.org"
 <linux-security-module@...r.kernel.org>, "nvdimm@...ts.linux.dev"
 <nvdimm@...ts.linux.dev>
Subject: Re: [PATCH] KEYS: encrypted: Add check for strsep

On Tue Jan 30, 2024 at 7:19 PM EET, Jarkko Sakkinen wrote:
> On Wed Jan 24, 2024 at 8:21 PM EET, Verma, Vishal L wrote:
> > On Wed, 2023-11-08 at 07:36 +0000, Chen Ni wrote:
> > > Add check for strsep() in order to transfer the error.
> > > 
> > > Fixes: cd3bc044af48 ("KEYS: encrypted: Instantiate key with user-
> > > provided decrypted data")
> > > Signed-off-by: Chen Ni <nichen@...as.ac.cn>
> > > ---
> > >  security/keys/encrypted-keys/encrypted.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/security/keys/encrypted-keys/encrypted.c
> > > b/security/keys/encrypted-keys/encrypted.c
> > > index 8af2136069d2..76f55dd13cb8 100644
> > > --- a/security/keys/encrypted-keys/encrypted.c
> > > +++ b/security/keys/encrypted-keys/encrypted.c
> > > @@ -237,6 +237,10 @@ static int datablob_parse(char *datablob, const
> > > char **format,
> > >  			break;
> > >  		}
> > >  		*decrypted_data = strsep(&datablob, " \t");
> > > +		if (!*decrypted_data) {
> > > +			pr_info("encrypted_key: decrypted_data is
> > > missing\n");
> > > +			break;
> > > +		}
> >
> > Hello,
> >
> > This patch seems to break keyring usage in CXL and NVDIMM, with the
> > "decrypted_data is missing" error path being hit. Reverting this commit
> > fixes the tests. I'm not sure if there are valid scenarios where this is
> > expected to be empty?
> >
> > Here's an strace snippet of where the error occurs:
> >
> >    keyctl(KEYCTL_SEARCH, KEY_SPEC_USER_KEYRING, "user", "nvdimm-master", 0) = 76300785
> >    openat(AT_FDCWD, "/sys/devices/platform/cxl_acpi.0/root0/nvdimm-bridge0/ndbus0/nmem0/state", O_RDONLY|O_CLOEXEC) = 3
> >    read(3, "idle\n", 1024)                 = 5
> >    close(3)                                = 0
> >    keyctl(KEYCTL_SEARCH, KEY_SPEC_USER_KEYRING, "encrypted", "nvdimm:0", 0) = -1 ENOKEY (Required key not available)
> >    uname({sysname="Linux", nodename="fedora", ...}) = 0
> >    newfstatat(AT_FDCWD, "/etc/ndctl/keys/nvdimm_0_fedora.blob", 0x7fff23fbc210, 0) = -1 ENOENT (No such file or directory)
> >    add_key("encrypted", "nvdimm:0", "new enc32 user:nvdimm-master 32", 31, KEY_SPEC_USER_KEYRING) = -1 EINVAL (Invalid argument)
> >    
>
> I think removing the klog message does not make sense meaning
> that the recent revert was wrong action taken.
>
> Instead necessary actions to retain backwards compatibility
> must be taken, meaning that the branch should set "ret = 0;".
>
> Motivation to keep it is dead obvious: your examples show that
> it can reveal potentially incorrect behaviour in user space
> software packages. It is info-level to mark that it can be
> also false positive. I.e. the revert commit takes away
> functionality that previously caused kernel masking a
> potential bug.
>
> Please revert the revert.
>
> BR, Jarkko

See the attached patch.

BR, Jarkko


View attachment "0001-KEYS-encrypted-Return-0-for-empty-decrypted-data.patch" of type "text/x-patch" (1110 bytes)