On Thursday, April 28, 2011 01:22:34 AM Casey Schaufler wrote: > On 4/27/2011 5:34 AM, Roberto Sassu wrote: > > The function smack_kernel_act_as() must return -EINVAL if the label > > returned by smack_from_secid() is equal to 'smack_known_invalid.smk_known', > > which means that no entries in the 'smack_known_list' list matching the > > security identifier given are found. > > I'll admit that the code here is wrong, but I disagree with the fix. > > smack_from_secid() will never return NULL, so the check for NULL is > pointless. Checking for known_invalid is not right either, as the > Smack philosophy is to return a label in all cases, as is evident > by the behavior of smack_from_secid(). Thus, the correct change > would be to remove the error check completely and set the new task > value to the value obtained from smack_from_secid in all cases. > > Besides, where did the caller of this function get a secid that isn't > going to map to a Smack label? > I discovered the issue when calling the function set_security_override_from_ctx(), located in kernel/cred.c, which will be used in eCryptfs to override the set of initial credentials (i'm about to post the patches). This function accepts an arbitrary string and uses it as a security label to replace the one in the credentials provided. If the string passed is not yet imported to SMACK, the 'smack_known_invalid.smk_known' label is applied without this fact is notified to the caller. I tried to solve the problem by importing the string during the execution of the security_secctx_to_secid() hook, so that set_security_override() will never fail. So, probably the string must be already been imported if no new memory can be allocated during smack_secctx_to_secid(). > > Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxx> > > --- > > security/smack/smack_lsm.c | 2 +- > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c > > index e3c9e54..0e7ed31 100644 > > --- a/security/smack/smack_lsm.c > > +++ b/security/smack/smack_lsm.c > > @@ -1415,7 +1415,7 @@ static int smack_kernel_act_as(struct cred *new, u32 secid) > > struct task_smack *new_tsp = new->security; > > char *smack = smack_from_secid(secid); > > > > - if (smack == NULL) > > + if (smack == smack_known_invalid.smk_known) > > return -EINVAL; > > > > new_tsp->smk_task = smack; > > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
