the following patch move the check for SMACK xattr size >= SMK_LABELLEN
from smack_inode_post_setxattr (which cannot return an error to the user)
to smack_inode_setxattr (which can return an error).
without patch a SMACK setxattr with size >= SMK_LABELLEN returns success although it doesn't
Signed-off-by: Etienne Basset <[email protected]>
---
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 9215149..da6954d 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -610,7 +610,8 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
if (!capable(CAP_MAC_ADMIN))
rc = -EPERM;
/* a label cannot be void and cannot begin with '-' */
- if (size == 0 || (size > 0 && ((char *)value)[0] == '-'))
+ if (size == 0 || size >= SMK_LABELLEN ||
+ (size > 0 && ((char *)value)[0] == '-'))
rc = -EINVAL;
} else
rc = cap_inode_setxattr(dentry, name, value, size, flags);
@@ -644,9 +645,6 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name,
if (strcmp(name, XATTR_NAME_SMACK))
return;
- if (size >= SMK_LABELLEN)
- return;
-
isp = dentry->d_inode->i_security;
/*
Etienne Basset wrote:
> the following patch move the check for SMACK xattr size >= SMK_LABELLEN
> from smack_inode_post_setxattr (which cannot return an error to the user)
> to smack_inode_setxattr (which can return an error).
>
> without patch a SMACK setxattr with size >= SMK_LABELLEN returns success although it doesn't
>
How about an early call to smk_import() to determine if the
label if legitimate, rather than checking the length? That
could save grief for other "invalid label" issues.
> Signed-off-by: Etienne Basset <[email protected]>
> ---
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 9215149..da6954d 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -610,7 +610,8 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
> if (!capable(CAP_MAC_ADMIN))
> rc = -EPERM;
> /* a label cannot be void and cannot begin with '-' */
> - if (size == 0 || (size > 0 && ((char *)value)[0] == '-'))
> + if (size == 0 || size >= SMK_LABELLEN ||
> + (size > 0 && ((char *)value)[0] == '-'))
> rc = -EINVAL;
> } else
> rc = cap_inode_setxattr(dentry, name, value, size, flags);
> @@ -644,9 +645,6 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name,
> if (strcmp(name, XATTR_NAME_SMACK))
> return;
>
> - if (size >= SMK_LABELLEN)
> - return;
> -
> isp = dentry->d_inode->i_security;
>
> /*
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
>
>
Casey Schaufler wrote:
> Etienne Basset wrote:
>> the following patch move the check for SMACK xattr size >= SMK_LABELLEN
>> from smack_inode_post_setxattr (which cannot return an error to the user)
>> to smack_inode_setxattr (which can return an error).
>>
>> without patch a SMACK setxattr with size >= SMK_LABELLEN returns success although it doesn't
>>
>
> How about an early call to smk_import() to determine if the
> label if legitimate, rather than checking the length? That
> could save grief for other "invalid label" issues.
Hi,
both are needed. And we'll need one call in setxattr to check the validity and one in
postsetxattr/ inode_setsecurity (to set the security blob)
(which make me think we should split smk_import in 2, smk_check/smk_import_nocheck or whatever)
The harder issue is that smk_import can change the value/size of the xattr
and smk_import can fail for 2 reasons : ENOMEM or EINVAL (not sure this is an issue though)
(we should really split)
root@etienne-desktop:/tmp# attr -S -s SMACK64 -V '123////' toto
Attribute "SMACK64" set to a 7 byte value for toto:
123////
root@etienne-desktop:/tmp# attr -S -g SMACK64 toto
Attribute "SMACK64" had a 4 byte value for toto:
123
maybe it would be nicer to fail than change the label under the foot of the-user-who-hasnt-read-the-doc?
Etienne
>
>> Signed-off-by: Etienne Basset <[email protected]>
>> ---
>> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
>> index 9215149..da6954d 100644
>> --- a/security/smack/smack_lsm.c
>> +++ b/security/smack/smack_lsm.c
>> @@ -610,7 +610,8 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
>> if (!capable(CAP_MAC_ADMIN))
>> rc = -EPERM;
>> /* a label cannot be void and cannot begin with '-' */
>> - if (size == 0 || (size > 0 && ((char *)value)[0] == '-'))
>> + if (size == 0 || size >= SMK_LABELLEN ||
>> + (size > 0 && ((char *)value)[0] == '-'))
>> rc = -EINVAL;
>> } else
>> rc = cap_inode_setxattr(dentry, name, value, size, flags);
>> @@ -644,9 +645,6 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name,
>> if (strcmp(name, XATTR_NAME_SMACK))
>> return;
>>
>> - if (size >= SMK_LABELLEN)
>> - return;
>> -
>> isp = dentry->d_inode->i_security;
>>
>> /*
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to [email protected]
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/
>>
>>
>>
>
>
Etienne Basset wrote:
> Casey Schaufler wrote:
>
>> Etienne Basset wrote:
>>
>>> the following patch move the check for SMACK xattr size >= SMK_LABELLEN
>>> from smack_inode_post_setxattr (which cannot return an error to the user)
>>> to smack_inode_setxattr (which can return an error).
>>>
>>> without patch a SMACK setxattr with size >= SMK_LABELLEN returns success although it doesn't
>>>
>>>
>> How about an early call to smk_import() to determine if the
>> label if legitimate, rather than checking the length? That
>> could save grief for other "invalid label" issues.
>>
>
> Hi,
>
> both are needed. And we'll need one call in setxattr to check the validity and one in
> postsetxattr/ inode_setsecurity (to set the security blob)
> (which make me think we should split smk_import in 2, smk_check/smk_import_nocheck or whatever)
>
> The harder issue is that smk_import can change the value/size of the xattr
> and smk_import can fail for 2 reasons : ENOMEM or EINVAL (not sure this is an issue though)
> (we should really split)
>
> root@etienne-desktop:/tmp# attr -S -s SMACK64 -V '123////' toto
> Attribute "SMACK64" set to a 7 byte value for toto:
> 123////
> root@etienne-desktop:/tmp# attr -S -g SMACK64 toto
> Attribute "SMACK64" had a 4 byte value for toto:
> 123
>
> maybe it would be nicer to fail than change the label under the foot of the-user-who-hasnt-read-the-doc?
>
Clumsy attribute setting (trailing spaces, NULLs, etc) is just too easy.
I like the existing behavior.
> Etienne
>
>>> Signed-off-by: Etienne Basset <[email protected]>
>>> ---
>>> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
>>> index 9215149..da6954d 100644
>>> --- a/security/smack/smack_lsm.c
>>> +++ b/security/smack/smack_lsm.c
>>> @@ -610,7 +610,8 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
>>> if (!capable(CAP_MAC_ADMIN))
>>> rc = -EPERM;
>>> /* a label cannot be void and cannot begin with '-' */
>>> - if (size == 0 || (size > 0 && ((char *)value)[0] == '-'))
>>> + if (size == 0 || size >= SMK_LABELLEN ||
>>> + (size > 0 && ((char *)value)[0] == '-'))
>>> rc = -EINVAL;
>>> } else
>>> rc = cap_inode_setxattr(dentry, name, value, size, flags);
>>> @@ -644,9 +645,6 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name,
>>> if (strcmp(name, XATTR_NAME_SMACK))
>>> return;
>>>
>>> - if (size >= SMK_LABELLEN)
>>> - return;
>>> -
>>> isp = dentry->d_inode->i_security;
>>>
>>> /*
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>> the body of a message to [email protected]
>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>> Please read the FAQ at http://www.tux.org/lkml/
>>>
>>>
>>>
>>>
>>
>
>
>
the following patch moves checks for SMACK xattr validity
from smack_inode_post_setxattr (which cannot return an error to the user)
to smack_inode_setxattr (which can return an error).
Signed-off-by: Etienne Basset <[email protected]>
---
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 9215149..98b3195 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -609,8 +609,12 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
strcmp(name, XATTR_NAME_SMACKIPOUT) == 0) {
if (!capable(CAP_MAC_ADMIN))
rc = -EPERM;
- /* a label cannot be void and cannot begin with '-' */
- if (size == 0 || (size > 0 && ((char *)value)[0] == '-'))
+ /*
+ * check label validity here so import wont fail on
+ * post_setxattr
+ */
+ if (size == 0 || size >= SMK_LABELLEN ||
+ smk_import(value, size) == NULL)
rc = -EINVAL;
} else
rc = cap_inode_setxattr(dentry, name, value, size, flags);
@@ -644,9 +648,6 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name,
if (strcmp(name, XATTR_NAME_SMACK))
return;
- if (size >= SMK_LABELLEN)
- return;
-
isp = dentry->d_inode->i_security;
/*
Etienne Basset wrote:
> the following patch moves checks for SMACK xattr validity
> from smack_inode_post_setxattr (which cannot return an error to the user)
> to smack_inode_setxattr (which can return an error).
>
> Signed-off-by: Etienne Basset <[email protected]>
>
Acked-by: Casey Schaufler <[email protected]>
> ---
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 9215149..98b3195 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -609,8 +609,12 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
> strcmp(name, XATTR_NAME_SMACKIPOUT) == 0) {
> if (!capable(CAP_MAC_ADMIN))
> rc = -EPERM;
> - /* a label cannot be void and cannot begin with '-' */
> - if (size == 0 || (size > 0 && ((char *)value)[0] == '-'))
> + /*
> + * check label validity here so import wont fail on
> + * post_setxattr
> + */
> + if (size == 0 || size >= SMK_LABELLEN ||
> + smk_import(value, size) == NULL)
> rc = -EINVAL;
> } else
> rc = cap_inode_setxattr(dentry, name, value, size, flags);
> @@ -644,9 +648,6 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name,
> if (strcmp(name, XATTR_NAME_SMACK))
> return;
>
> - if (size >= SMK_LABELLEN)
> - return;
> -
> isp = dentry->d_inode->i_security;
>
> /*
>
>
>
>