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Message-ID: <20110620144035.GB11750@albatros> Date: Mon, 20 Jun 2011 18:40:35 +0400 From: Vasiliy Kulikov <segoon@...nwall.com> To: Eric Paris <eparis@...hat.com> Cc: linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, apparmor@...ts.ubuntu.com, "selinux@...ho.nsa.gov Stephen Smalley" <sds@...ho.nsa.gov>, James Morris <jmorris@...ei.org>, Eric Paris <eparis@...isplace.org>, John Johansen <john.johansen@...onical.com>, kernel-hardening@...ts.openwall.com, serge@...lyn.com Subject: Re: [RFC v2] security: intoduce ptrace_task_may_access_current Hi Eric, On Mon, Jun 20, 2011 at 10:22 -0400, Eric Paris wrote: > >diff --git a/include/linux/capability.h b/include/linux/capability.h > >index c421123..cc0bcfe 100644 > >--- a/include/linux/capability.h > >+++ b/include/linux/capability.h > >@@ -544,7 +544,9 @@ extern bool has_ns_capability(struct task_struct *t, > > struct user_namespace *ns, int cap); > > extern bool has_capability_noaudit(struct task_struct *t, int cap); > > extern bool capable(int cap); > >+extern bool task_capable(struct task_struct *task, int cap); > > extern bool ns_capable(struct user_namespace *ns, int cap); > >+extern bool ns_task_capable(struct task_struct *t, struct user_namespace *ns, int cap); > > extern bool task_ns_capable(struct task_struct *t, int cap); > > now we have ns_task_capable() and task_ns_capable() ? What is the > difference? Why do I have 2? Which one do I choose where? Hmmm, agreed, I didn't spot it. > >diff --git a/include/linux/security.h b/include/linux/security.h > >index 8ce59ef..fb79dd5 100644 > >--- a/include/linux/security.h > >+++ b/include/linux/security.h > >@@ -56,7 +56,8 @@ struct user_namespace; > > extern int cap_capable(struct task_struct *tsk, const struct cred *cred, > > struct user_namespace *ns, int cap, int audit); > > extern int cap_settime(const struct timespec *ts, const struct timezone *tz); > >-extern int cap_ptrace_access_check(struct task_struct *child, unsigned int mode); > >+extern int cap_ptrace_access_check(struct task_struct *task, struct task_struct *child, > >+ unsigned int mode); > > extern int cap_ptrace_traceme(struct task_struct *parent); > > extern int cap_capget(struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted); > > extern int cap_capset(struct cred *new, const struct cred *old, > >@@ -1375,7 +1376,9 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts) > > struct security_operations { > > char name[SECURITY_NAME_MAX + 1]; > > > >- int (*ptrace_access_check) (struct task_struct *child, unsigned int mode); > >+ int (*ptrace_access_check) (struct task_struct *task, > >+ struct task_struct *child, > >+ unsigned int mode); > > formatting nit, this patch lines up args, it doesn't just use tabs > for the 2nd/3rd line. OK. > > int (*ptrace_traceme) (struct task_struct *parent); > > int (*capget) (struct task_struct *target, > > kernel_cap_t *effective, > >@@ -1657,6 +1660,8 @@ extern int security_module_enable(struct security_operations *ops); > > extern int register_security(struct security_operations *ops); > > > > /* Security operations */ > >+int security_ptrace_task_access_check(struct task_struct *task, > >+ struct task_struct *child, unsigned int mode); > > I thought we agreed to not add a new ptrace_task_access_check(), > just fix security_ptrace_access_check() to take the new argument. I did it for security ops, will do it for security_ptrace_access_check() too. > > int security_ptrace_access_check(struct task_struct *child, unsigned int mode); > > int security_ptrace_traceme(struct task_struct *parent); > > int security_capget(struct task_struct *target, > >@@ -1667,6 +1672,10 @@ int security_capset(struct cred *new, const struct cred *old, > > const kernel_cap_t *effective, > > const kernel_cap_t *inheritable, > > const kernel_cap_t *permitted); > >+int security_task_capable(struct task_struct *task, > >+ struct user_namespace *ns, > >+ const struct cred *cred, > >+ int cap); > > Personally I don't love this either and think we should just > redefine security_capable. OK. > > int security_capable(struct user_namespace *ns, const struct cred *cred, > > int cap); > > int security_real_capable(struct task_struct *tsk, struct user_namespace *ns, > >@@ -1837,10 +1846,16 @@ static inline int security_init(void) > > return 0; > > } > > > >+static inline int security_ptrace_task_access_check(struct task_struct *task, > >+ struct task_struct *child, unsigned int mode) > >+{ > >+ return cap_ptrace_access_check(task, child, mode); > >+} > >+ > > static inline int security_ptrace_access_check(struct task_struct *child, > > unsigned int mode) > > { > >- return cap_ptrace_access_check(child, mode); > >+ return cap_ptrace_access_check(current, child, mode); > > } > > Lets not introduce security_ptrace_task_access_check() at all. Just > add the new argument to security_ptrace_access_check() and fix the > single caller (it looks to me like security_ptrace_access_check() > has no users after this patch) OK. > > > > static inline int security_ptrace_traceme(struct task_struct *parent) > >@@ -1865,10 +1880,18 @@ static inline int security_capset(struct cred *new, > > return cap_capset(new, old, effective, inheritable, permitted); > > } > > > >+static inline int security_task_capable(struct task_struct *task, > >+ struct user_namespace *ns, > >+ const struct cred *cred, > >+ int cap) > >+{ > >+ return cap_capable(task, cred, ns, cap, SECURITY_CAP_AUDIT); > >+} > >+ > > static inline int security_capable(struct user_namespace *ns, > > const struct cred *cred, int cap) > > { > >- return cap_capable(current, cred, ns, cap, SECURITY_CAP_AUDIT); > >+ return security_task_capable(current, ns, cred, cap); > > } > > There is only one caller of security_capable outside in the kernel. > Can we just add the task argument rather than make a new function? > Even if you want to retain security_capable, define it exactly like > this up where you declared the function and remove it everywhere > else in the code base. OK. > > static inline int security_real_capable(struct task_struct *tsk, struct user_namespace *ns, int cap) > >diff --git a/kernel/capability.c b/kernel/capability.c > >index 283c529..bc9b07f 100644 > >--- a/kernel/capability.c > >+++ b/kernel/capability.c > >@@ -356,6 +356,30 @@ bool capable(int cap) > > } > > EXPORT_SYMBOL(capable); > > > >+bool task_capable(struct task_struct *task, int cap) > >+{ > >+ return ns_task_capable(task,&init_user_ns, cap); > >+} > >+EXPORT_SYMBOL(task_capable); > > Why do we keep adding things like task_capable? Can't we just stop > adding non-lsm functions and just call the right LSM functions from > now on? This is my original comments mostly directed at Serge. I'm > to the point where I want to NAK anything new in kernel/capability.c > (and yes, I know i'm guilty in the paste) > > >+bool ns_task_capable(struct task_struct *task, struct user_namespace *ns, int cap) > >+{ > >+ if (unlikely(!cap_valid(cap))) { > >+ printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap); > >+ BUG(); > >+ } > >+ > >+ rcu_read_lock(); > >+ if (security_task_capable(task, ns, __task_cred(task), cap) == 0) { > >+ rcu_read_unlock(); > >+ current->flags |= PF_SUPERPRIV; (fixing my 2 copy-paste bugs, here and below) s/current/task/ > >+ return true; > >+ } > >+ rcu_read_unlock(); > >+ return false; > >+} > >+EXPORT_SYMBOL(ns_task_capable); > > Ok, NAK. I just can' stomache having a ns_task_capable() and a > task_ns_capable(). One of them has to be wrong. I'm a bit confused with numerous capable funtions too, but I thought they are needed for some abstraction level. I'll remove ns_task_capable(). > >+ > > /** > > * ns_capable - Determine if the current task has a superior capability in effect > > * @ns: The usernamespace we want the capability in > >@@ -369,16 +393,7 @@ EXPORT_SYMBOL(capable); > > */ > > bool ns_capable(struct user_namespace *ns, int cap) > > { > >- if (unlikely(!cap_valid(cap))) { > >- printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap); > >- BUG(); > >- } > >- > >- if (security_capable(ns, current_cred(), cap) == 0) { > >- current->flags |= PF_SUPERPRIV; > >- return true; > >- } > >- return false; > >+ return ns_task_capable(current, ns, cap); > > } > > EXPORT_SYMBOL(ns_capable); > > > >diff --git a/kernel/ptrace.c b/kernel/ptrace.c > >index 2df1157..df8fe32 100644 > >--- a/kernel/ptrace.c > >+++ b/kernel/ptrace.c > >@@ -132,9 +132,9 @@ int ptrace_check_attach(struct task_struct *child, int kill) > > return ret; > > } > > > >-int __ptrace_may_access(struct task_struct *task, unsigned int mode) > >+int __ptrace_may_access(struct task_struct *who, struct task_struct *task, unsigned int mode) > > { > >- const struct cred *cred = current_cred(), *tcred; > >+ const struct cred *cred, *tcred; > > > > /* May we inspect the given task? > > * This check is used both for attaching with ptrace > >@@ -149,6 +149,7 @@ int __ptrace_may_access(struct task_struct *task, unsigned int mode) > > if (task == current) s/current/who/ -- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments
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