Re: [PATCH] KEYS: encrypted: Add check for strsep

["Jarkko Sakkinen" <jarkko@kernel.org>]

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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@iscas.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

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From cdfa4203c86412af39b232eaa7401591451659de Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <jarkko@kernel.org>
Date: Tue, 30 Jan 2024 19:11:50 +0200
Subject: [PATCH] KEYS: encrypted: Return 0 for empty decrypted data

Return 0 to return backwards comptibility but *do keep* the klog entry
for foresincs sake.

Fixes: b4af096b5df5 ("KEYS: encrypted: Add check for strsep")
Link: https://lore.kernel.org/keyrings/4d3465b48b9c5a87deb385b15bf5125fc1704019.camel@intel.com/
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 security/keys/encrypted-keys/encrypted.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index 76f55dd13cb8..e3173141027e 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -225,6 +225,7 @@ static int datablob_parse(char *datablob, const char **format,
 		*decrypted_datalen = strsep(&datablob, " \t");
 		if (!*decrypted_datalen) {
 			pr_info("encrypted_key: keylen parameter is missing\n");
+			ret = 0;
 			goto out;
 		}
 	}
-- 
2.40.1