The original justification for cap_task_kill() was as follows:
check_kill_permission() does appropriate uid equivalence checks.
However with file capabilities it becomes possible for an
unprivileged user to execute a file with file capabilities
resulting in a more privileged task with the same uid.
However now that cap_task_kill() always returns 0 (permission
granted) when p->uid==current->uid, the whole hook is worthless,
and only likely to create more subtle problems in the corner cases
where it might still be called but return -EPERM. Those cases
are basically when uids are different but euid/suid is equivalent
as per the check in check_kill_permission().
This patch removes cap_task_kill().
Signed-off-by: Serge Hallyn <[email protected]>
---
include/linux/security.h | 3 +--
security/capability.c | 1 -
security/commoncap.c | 40 ----------------------------------------
security/smack/smack_lsm.c | 5 -----
4 files changed, 1 insertions(+), 48 deletions(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index fe52cde..95cb830 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -63,7 +63,6 @@ extern int cap_inode_need_killpriv(struct dentry *dentry);
extern int cap_inode_killpriv(struct dentry *dentry);
extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags);
extern void cap_task_reparent_to_init (struct task_struct *p);
-extern int cap_task_kill(struct task_struct *p, struct siginfo *info, int sig, u32 secid);
extern int cap_task_setscheduler (struct task_struct *p, int policy, struct sched_param *lp);
extern int cap_task_setioprio (struct task_struct *p, int ioprio);
extern int cap_task_setnice (struct task_struct *p, int nice);
@@ -2138,7 +2137,7 @@ static inline int security_task_kill (struct task_struct *p,
struct siginfo *info, int sig,
u32 secid)
{
- return cap_task_kill(p, info, sig, secid);
+ return 0;
}
static inline int security_task_wait (struct task_struct *p)
diff --git a/security/capability.c b/security/capability.c
index 9e99f36..2c6e06d 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -40,7 +40,6 @@ static struct security_operations capability_ops = {
.inode_need_killpriv = cap_inode_need_killpriv,
.inode_killpriv = cap_inode_killpriv,
- .task_kill = cap_task_kill,
.task_setscheduler = cap_task_setscheduler,
.task_setioprio = cap_task_setioprio,
.task_setnice = cap_task_setnice,
diff --git a/security/commoncap.c b/security/commoncap.c
index bb0c095..06d5c94 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -540,41 +540,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
return cap_safe_nice(p);
}
-int cap_task_kill(struct task_struct *p, struct siginfo *info,
- int sig, u32 secid)
-{
- if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info)))
- return 0;
-
- /*
- * Running a setuid root program raises your capabilities.
- * Killing your own setuid root processes was previously
- * allowed.
- * We must preserve legacy signal behavior in this case.
- */
- if (p->uid == current->uid)
- return 0;
-
- /* sigcont is permitted within same session */
- if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p)))
- return 0;
-
- if (secid)
- /*
- * Signal sent as a particular user.
- * Capabilities are ignored. May be wrong, but it's the
- * only thing we can do at the moment.
- * Used only by usb drivers?
- */
- return 0;
- if (cap_issubset(p->cap_permitted, current->cap_permitted))
- return 0;
- if (capable(CAP_KILL))
- return 0;
-
- return -EPERM;
-}
-
/*
* called from kernel/sys.c for prctl(PR_CABSET_DROP)
* done without task_capability_lock() because it introduces
@@ -605,11 +570,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
{
return 0;
}
-int cap_task_kill(struct task_struct *p, struct siginfo *info,
- int sig, u32 secid)
-{
- return 0;
-}
#endif
void cap_task_reparent_to_init (struct task_struct *p)
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 770eb06..a9ca412 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1124,11 +1124,6 @@ static int smack_task_movememory(struct task_struct *p)
static int smack_task_kill(struct task_struct *p, struct siginfo *info,
int sig, u32 secid)
{
- int rc;
-
- rc = cap_task_kill(p, info, sig, secid);
- if (rc != 0)
- return rc;
/*
* Special cases where signals really ought to go through
* in spite of policy. Stephen Smalley suggests it may
--
1.5.2.5
For 2.6.25-rc3,
Tested-By: John Gatewood Ham <[email protected]>
This fixes the 'at' command for non-root users. Thank you.
On 2/29/08, [email protected] <[email protected]> wrote:
> The original justification for cap_task_kill() was as follows:
>
> check_kill_permission() does appropriate uid equivalence checks.
> However with file capabilities it becomes possible for an
> unprivileged user to execute a file with file capabilities
> resulting in a more privileged task with the same uid.
>
> However now that cap_task_kill() always returns 0 (permission
> granted) when p->uid==current->uid, the whole hook is worthless,
> and only likely to create more subtle problems in the corner cases
> where it might still be called but return -EPERM. Those cases
> are basically when uids are different but euid/suid is equivalent
> as per the check in check_kill_permission().
>
> This patch removes cap_task_kill().
>
> Signed-off-by: Serge Hallyn <[email protected]>
> ---
> include/linux/security.h | 3 +--
> security/capability.c | 1 -
> security/commoncap.c | 40 ----------------------------------------
> security/smack/smack_lsm.c | 5 -----
> 4 files changed, 1 insertions(+), 48 deletions(-)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index fe52cde..95cb830 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -63,7 +63,6 @@ extern int cap_inode_need_killpriv(struct dentry *dentry);
> extern int cap_inode_killpriv(struct dentry *dentry);
> extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t
> old_suid, int flags);
> extern void cap_task_reparent_to_init (struct task_struct *p);
> -extern int cap_task_kill(struct task_struct *p, struct siginfo *info, int
> sig, u32 secid);
> extern int cap_task_setscheduler (struct task_struct *p, int policy, struct
> sched_param *lp);
> extern int cap_task_setioprio (struct task_struct *p, int ioprio);
> extern int cap_task_setnice (struct task_struct *p, int nice);
> @@ -2138,7 +2137,7 @@ static inline int security_task_kill (struct
> task_struct *p,
> struct siginfo *info, int sig,
> u32 secid)
> {
> - return cap_task_kill(p, info, sig, secid);
> + return 0;
> }
>
> static inline int security_task_wait (struct task_struct *p)
> diff --git a/security/capability.c b/security/capability.c
> index 9e99f36..2c6e06d 100644
> --- a/security/capability.c
> +++ b/security/capability.c
> @@ -40,7 +40,6 @@ static struct security_operations capability_ops = {
> .inode_need_killpriv = cap_inode_need_killpriv,
> .inode_killpriv = cap_inode_killpriv,
>
> - .task_kill = cap_task_kill,
> .task_setscheduler = cap_task_setscheduler,
> .task_setioprio = cap_task_setioprio,
> .task_setnice = cap_task_setnice,
> diff --git a/security/commoncap.c b/security/commoncap.c
> index bb0c095..06d5c94 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -540,41 +540,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
> return cap_safe_nice(p);
> }
>
> -int cap_task_kill(struct task_struct *p, struct siginfo *info,
> - int sig, u32 secid)
> -{
> - if (info != SEND_SIG_NOINFO && (is_si_special(info) ||
> SI_FROMKERNEL(info)))
> - return 0;
> -
> - /*
> - * Running a setuid root program raises your capabilities.
> - * Killing your own setuid root processes was previously
> - * allowed.
> - * We must preserve legacy signal behavior in this case.
> - */
> - if (p->uid == current->uid)
> - return 0;
> -
> - /* sigcont is permitted within same session */
> - if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p)))
> - return 0;
> -
> - if (secid)
> - /*
> - * Signal sent as a particular user.
> - * Capabilities are ignored. May be wrong, but it's the
> - * only thing we can do at the moment.
> - * Used only by usb drivers?
> - */
> - return 0;
> - if (cap_issubset(p->cap_permitted, current->cap_permitted))
> - return 0;
> - if (capable(CAP_KILL))
> - return 0;
> -
> - return -EPERM;
> -}
> -
> /*
> * called from kernel/sys.c for prctl(PR_CABSET_DROP)
> * done without task_capability_lock() because it introduces
> @@ -605,11 +570,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
> {
> return 0;
> }
> -int cap_task_kill(struct task_struct *p, struct siginfo *info,
> - int sig, u32 secid)
> -{
> - return 0;
> -}
> #endif
>
> void cap_task_reparent_to_init (struct task_struct *p)
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 770eb06..a9ca412 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -1124,11 +1124,6 @@ static int smack_task_movememory(struct task_struct
> *p)
> static int smack_task_kill(struct task_struct *p, struct siginfo *info,
> int sig, u32 secid)
> {
> - int rc;
> -
> - rc = cap_task_kill(p, info, sig, secid);
> - if (rc != 0)
> - return rc;
> /*
> * Special cases where signals really ought to go through
> * in spite of policy. Stephen Smalley suggests it may
> --
> 1.5.2.5
>
>
Quoting BuraphaLinux Server ([email protected]):
> For 2.6.25-rc3,
> Tested-By: John Gatewood Ham <[email protected]>
>
> This fixes the 'at' command for non-root users. Thank you.
Cool, thanks much for testing.
-serge
> On 2/29/08, [email protected] <[email protected]> wrote:
> > The original justification for cap_task_kill() was as follows:
> >
> > check_kill_permission() does appropriate uid equivalence checks.
> > However with file capabilities it becomes possible for an
> > unprivileged user to execute a file with file capabilities
> > resulting in a more privileged task with the same uid.
> >
> > However now that cap_task_kill() always returns 0 (permission
> > granted) when p->uid==current->uid, the whole hook is worthless,
> > and only likely to create more subtle problems in the corner cases
> > where it might still be called but return -EPERM. Those cases
> > are basically when uids are different but euid/suid is equivalent
> > as per the check in check_kill_permission().
> >
> > This patch removes cap_task_kill().
> >
> > Signed-off-by: Serge Hallyn <[email protected]>
> > ---
> > include/linux/security.h | 3 +--
> > security/capability.c | 1 -
> > security/commoncap.c | 40 ----------------------------------------
> > security/smack/smack_lsm.c | 5 -----
> > 4 files changed, 1 insertions(+), 48 deletions(-)
> >
> > diff --git a/include/linux/security.h b/include/linux/security.h
> > index fe52cde..95cb830 100644
> > --- a/include/linux/security.h
> > +++ b/include/linux/security.h
> > @@ -63,7 +63,6 @@ extern int cap_inode_need_killpriv(struct dentry *dentry);
> > extern int cap_inode_killpriv(struct dentry *dentry);
> > extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t
> > old_suid, int flags);
> > extern void cap_task_reparent_to_init (struct task_struct *p);
> > -extern int cap_task_kill(struct task_struct *p, struct siginfo *info, int
> > sig, u32 secid);
> > extern int cap_task_setscheduler (struct task_struct *p, int policy, struct
> > sched_param *lp);
> > extern int cap_task_setioprio (struct task_struct *p, int ioprio);
> > extern int cap_task_setnice (struct task_struct *p, int nice);
> > @@ -2138,7 +2137,7 @@ static inline int security_task_kill (struct
> > task_struct *p,
> > struct siginfo *info, int sig,
> > u32 secid)
> > {
> > - return cap_task_kill(p, info, sig, secid);
> > + return 0;
> > }
> >
> > static inline int security_task_wait (struct task_struct *p)
> > diff --git a/security/capability.c b/security/capability.c
> > index 9e99f36..2c6e06d 100644
> > --- a/security/capability.c
> > +++ b/security/capability.c
> > @@ -40,7 +40,6 @@ static struct security_operations capability_ops = {
> > .inode_need_killpriv = cap_inode_need_killpriv,
> > .inode_killpriv = cap_inode_killpriv,
> >
> > - .task_kill = cap_task_kill,
> > .task_setscheduler = cap_task_setscheduler,
> > .task_setioprio = cap_task_setioprio,
> > .task_setnice = cap_task_setnice,
> > diff --git a/security/commoncap.c b/security/commoncap.c
> > index bb0c095..06d5c94 100644
> > --- a/security/commoncap.c
> > +++ b/security/commoncap.c
> > @@ -540,41 +540,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
> > return cap_safe_nice(p);
> > }
> >
> > -int cap_task_kill(struct task_struct *p, struct siginfo *info,
> > - int sig, u32 secid)
> > -{
> > - if (info != SEND_SIG_NOINFO && (is_si_special(info) ||
> > SI_FROMKERNEL(info)))
> > - return 0;
> > -
> > - /*
> > - * Running a setuid root program raises your capabilities.
> > - * Killing your own setuid root processes was previously
> > - * allowed.
> > - * We must preserve legacy signal behavior in this case.
> > - */
> > - if (p->uid == current->uid)
> > - return 0;
> > -
> > - /* sigcont is permitted within same session */
> > - if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p)))
> > - return 0;
> > -
> > - if (secid)
> > - /*
> > - * Signal sent as a particular user.
> > - * Capabilities are ignored. May be wrong, but it's the
> > - * only thing we can do at the moment.
> > - * Used only by usb drivers?
> > - */
> > - return 0;
> > - if (cap_issubset(p->cap_permitted, current->cap_permitted))
> > - return 0;
> > - if (capable(CAP_KILL))
> > - return 0;
> > -
> > - return -EPERM;
> > -}
> > -
> > /*
> > * called from kernel/sys.c for prctl(PR_CABSET_DROP)
> > * done without task_capability_lock() because it introduces
> > @@ -605,11 +570,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
> > {
> > return 0;
> > }
> > -int cap_task_kill(struct task_struct *p, struct siginfo *info,
> > - int sig, u32 secid)
> > -{
> > - return 0;
> > -}
> > #endif
> >
> > void cap_task_reparent_to_init (struct task_struct *p)
> > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> > index 770eb06..a9ca412 100644
> > --- a/security/smack/smack_lsm.c
> > +++ b/security/smack/smack_lsm.c
> > @@ -1124,11 +1124,6 @@ static int smack_task_movememory(struct task_struct
> > *p)
> > static int smack_task_kill(struct task_struct *p, struct siginfo *info,
> > int sig, u32 secid)
> > {
> > - int rc;
> > -
> > - rc = cap_task_kill(p, info, sig, secid);
> > - if (rc != 0)
> > - return rc;
> > /*
> > * Special cases where signals really ought to go through
> > * in spite of policy. Stephen Smalley suggests it may
> > --
> > 1.5.2.5
> >
> >
> --
> To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
Em Thu, 28 Feb 2008 11:38:17 -0600
[email protected] escreveu:
| The original justification for cap_task_kill() was as follows:
|
| check_kill_permission() does appropriate uid equivalence checks.
| However with file capabilities it becomes possible for an
| unprivileged user to execute a file with file capabilities
| resulting in a more privileged task with the same uid.
|
| However now that cap_task_kill() always returns 0 (permission
| granted) when p->uid==current->uid, the whole hook is worthless,
| and only likely to create more subtle problems in the corner cases
| where it might still be called but return -EPERM. Those cases
| are basically when uids are different but euid/suid is equivalent
| as per the check in check_kill_permission().
|
| This patch removes cap_task_kill().
2.6.24 seems to have the same bug, what about a rediff for it and
submit the patch to -stable team?
Thanks.
--
Luiz Fernando N. Capitulino
Quoting Luiz Fernando N. Capitulino ([email protected]):
> Em Thu, 28 Feb 2008 11:38:17 -0600
> [email protected] escreveu:
>
> | The original justification for cap_task_kill() was as follows:
> |
> | check_kill_permission() does appropriate uid equivalence checks.
> | However with file capabilities it becomes possible for an
> | unprivileged user to execute a file with file capabilities
> | resulting in a more privileged task with the same uid.
> |
> | However now that cap_task_kill() always returns 0 (permission
> | granted) when p->uid==current->uid, the whole hook is worthless,
> | and only likely to create more subtle problems in the corner cases
> | where it might still be called but return -EPERM. Those cases
> | are basically when uids are different but euid/suid is equivalent
> | as per the check in check_kill_permission().
> |
> | This patch removes cap_task_kill().
>
> 2.6.24 seems to have the same bug, what about a rediff for it and
> submit the patch to -stable team?
Luiz, could you confirm that the below works?
thanks,
-serge
>From c77b7d418933c14707383f06a1da61169e84071b Mon Sep 17 00:00:00 2001
From: Serge Hallyn <[email protected]>
Date: Fri, 29 Feb 2008 15:14:57 +0000
Subject: [PATCH 1/1] file capabilities: remove cap_task_kill()
The original justification for cap_task_kill() was as follows:
check_kill_permission() does appropriate uid equivalence checks.
However with file capabilities it becomes possible for an
unprivileged user to execute a file with file capabilities
resulting in a more privileged task with the same uid.
However now that cap_task_kill() always returns 0 (permission
granted) when p->uid==current->uid, the whole hook is worthless,
and only likely to create more subtle problems in the corner cases
where it might still be called but return -EPERM. Those cases
are basically when uids are different but euid/suid is equivalent
as per the check in check_kill_permission().
This patch removes cap_task_kill().
Signed-off-by: Serge Hallyn <[email protected]>
---
include/linux/security.h | 3 +--
security/capability.c | 1 -
security/commoncap.c | 39 ---------------------------------------
3 files changed, 1 insertions(+), 42 deletions(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index ac05083..d842ee3 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -62,7 +62,6 @@ extern int cap_inode_need_killpriv(struct dentry *dentry);
extern int cap_inode_killpriv(struct dentry *dentry);
extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags);
extern void cap_task_reparent_to_init (struct task_struct *p);
-extern int cap_task_kill(struct task_struct *p, struct siginfo *info, int sig, u32 secid);
extern int cap_task_setscheduler (struct task_struct *p, int policy, struct sched_param *lp);
extern int cap_task_setioprio (struct task_struct *p, int ioprio);
extern int cap_task_setnice (struct task_struct *p, int nice);
@@ -2112,7 +2111,7 @@ static inline int security_task_kill (struct task_struct *p,
struct siginfo *info, int sig,
u32 secid)
{
- return cap_task_kill(p, info, sig, secid);
+ return 0;
}
static inline int security_task_wait (struct task_struct *p)
diff --git a/security/capability.c b/security/capability.c
index 9e99f36..2c6e06d 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -40,7 +40,6 @@ static struct security_operations capability_ops = {
.inode_need_killpriv = cap_inode_need_killpriv,
.inode_killpriv = cap_inode_killpriv,
- .task_kill = cap_task_kill,
.task_setscheduler = cap_task_setscheduler,
.task_setioprio = cap_task_setioprio,
.task_setnice = cap_task_setnice,
diff --git a/security/commoncap.c b/security/commoncap.c
index ea61bc7..6e9065c 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -527,40 +527,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
return cap_safe_nice(p);
}
-int cap_task_kill(struct task_struct *p, struct siginfo *info,
- int sig, u32 secid)
-{
- if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info)))
- return 0;
-
- /*
- * Running a setuid root program raises your capabilities.
- * Killing your own setuid root processes was previously
- * allowed.
- * We must preserve legacy signal behavior in this case.
- */
- if (p->euid == 0 && p->uid == current->uid)
- return 0;
-
- /* sigcont is permitted within same session */
- if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p)))
- return 0;
-
- if (secid)
- /*
- * Signal sent as a particular user.
- * Capabilities are ignored. May be wrong, but it's the
- * only thing we can do at the moment.
- * Used only by usb drivers?
- */
- return 0;
- if (cap_issubset(p->cap_permitted, current->cap_permitted))
- return 0;
- if (capable(CAP_KILL))
- return 0;
-
- return -EPERM;
-}
#else
int cap_task_setscheduler (struct task_struct *p, int policy,
struct sched_param *lp)
@@ -575,11 +541,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
{
return 0;
}
-int cap_task_kill(struct task_struct *p, struct siginfo *info,
- int sig, u32 secid)
-{
- return 0;
-}
#endif
void cap_task_reparent_to_init (struct task_struct *p)
--
1.5.2.5
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Acked-by: Andrew G. Morgan <[email protected]>
Cheers
Andrew
[email protected] wrote:
| The original justification for cap_task_kill() was as follows:
|
| check_kill_permission() does appropriate uid equivalence checks.
| However with file capabilities it becomes possible for an
| unprivileged user to execute a file with file capabilities
| resulting in a more privileged task with the same uid.
|
| However now that cap_task_kill() always returns 0 (permission
| granted) when p->uid==current->uid, the whole hook is worthless,
| and only likely to create more subtle problems in the corner cases
| where it might still be called but return -EPERM. Those cases
| are basically when uids are different but euid/suid is equivalent
| as per the check in check_kill_permission().
|
| This patch removes cap_task_kill().
|
| Signed-off-by: Serge Hallyn <[email protected]>
| ---
| include/linux/security.h | 3 +--
| security/capability.c | 1 -
| security/commoncap.c | 40
- ----------------------------------------
| security/smack/smack_lsm.c | 5 -----
| 4 files changed, 1 insertions(+), 48 deletions(-)
|
| diff --git a/include/linux/security.h b/include/linux/security.h
| index fe52cde..95cb830 100644
| --- a/include/linux/security.h
| +++ b/include/linux/security.h
| @@ -63,7 +63,6 @@ extern int cap_inode_need_killpriv(struct dentry
*dentry);
| extern int cap_inode_killpriv(struct dentry *dentry);
| extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid,
uid_t old_suid, int flags);
| extern void cap_task_reparent_to_init (struct task_struct *p);
| -extern int cap_task_kill(struct task_struct *p, struct siginfo *info,
int sig, u32 secid);
| extern int cap_task_setscheduler (struct task_struct *p, int policy,
struct sched_param *lp);
| extern int cap_task_setioprio (struct task_struct *p, int ioprio);
| extern int cap_task_setnice (struct task_struct *p, int nice);
| @@ -2138,7 +2137,7 @@ static inline int security_task_kill (struct
task_struct *p,
| struct siginfo *info, int sig,
| u32 secid)
| {
| - return cap_task_kill(p, info, sig, secid);
| + return 0;
| }
|
| static inline int security_task_wait (struct task_struct *p)
| diff --git a/security/capability.c b/security/capability.c
| index 9e99f36..2c6e06d 100644
| --- a/security/capability.c
| +++ b/security/capability.c
| @@ -40,7 +40,6 @@ static struct security_operations capability_ops = {
| .inode_need_killpriv = cap_inode_need_killpriv,
| .inode_killpriv = cap_inode_killpriv,
|
| - .task_kill = cap_task_kill,
| .task_setscheduler = cap_task_setscheduler,
| .task_setioprio = cap_task_setioprio,
| .task_setnice = cap_task_setnice,
| diff --git a/security/commoncap.c b/security/commoncap.c
| index bb0c095..06d5c94 100644
| --- a/security/commoncap.c
| +++ b/security/commoncap.c
| @@ -540,41 +540,6 @@ int cap_task_setnice (struct task_struct *p, int
nice)
| return cap_safe_nice(p);
| }
|
| -int cap_task_kill(struct task_struct *p, struct siginfo *info,
| - int sig, u32 secid)
| -{
| - if (info != SEND_SIG_NOINFO && (is_si_special(info) ||
SI_FROMKERNEL(info)))
| - return 0;
| -
| - /*
| - * Running a setuid root program raises your capabilities.
| - * Killing your own setuid root processes was previously
| - * allowed.
| - * We must preserve legacy signal behavior in this case.
| - */
| - if (p->uid == current->uid)
| - return 0;
| -
| - /* sigcont is permitted within same session */
| - if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p)))
| - return 0;
| -
| - if (secid)
| - /*
| - * Signal sent as a particular user.
| - * Capabilities are ignored. May be wrong, but it's the
| - * only thing we can do at the moment.
| - * Used only by usb drivers?
| - */
| - return 0;
| - if (cap_issubset(p->cap_permitted, current->cap_permitted))
| - return 0;
| - if (capable(CAP_KILL))
| - return 0;
| -
| - return -EPERM;
| -}
| -
| /*
| * called from kernel/sys.c for prctl(PR_CABSET_DROP)
| * done without task_capability_lock() because it introduces
| @@ -605,11 +570,6 @@ int cap_task_setnice (struct task_struct *p, int
nice)
| {
| return 0;
| }
| -int cap_task_kill(struct task_struct *p, struct siginfo *info,
| - int sig, u32 secid)
| -{
| - return 0;
| -}
| #endif
|
| void cap_task_reparent_to_init (struct task_struct *p)
| diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
| index 770eb06..a9ca412 100644
| --- a/security/smack/smack_lsm.c
| +++ b/security/smack/smack_lsm.c
| @@ -1124,11 +1124,6 @@ static int smack_task_movememory(struct
task_struct *p)
| static int smack_task_kill(struct task_struct *p, struct siginfo *info,
| int sig, u32 secid)
| {
| - int rc;
| -
| - rc = cap_task_kill(p, info, sig, secid);
| - if (rc != 0)
| - return rc;
| /*
| * Special cases where signals really ought to go through
| * in spite of policy. Stephen Smalley suggests it may
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Em Fri, 29 Feb 2008 15:26:34 -0600
[email protected] escreveu:
| Quoting Luiz Fernando N. Capitulino ([email protected]):
| > Em Thu, 28 Feb 2008 11:38:17 -0600
| > [email protected] escreveu:
| >
| > | The original justification for cap_task_kill() was as follows:
| > |
| > | check_kill_permission() does appropriate uid equivalence checks.
| > | However with file capabilities it becomes possible for an
| > | unprivileged user to execute a file with file capabilities
| > | resulting in a more privileged task with the same uid.
| > |
| > | However now that cap_task_kill() always returns 0 (permission
| > | granted) when p->uid==current->uid, the whole hook is worthless,
| > | and only likely to create more subtle problems in the corner cases
| > | where it might still be called but return -EPERM. Those cases
| > | are basically when uids are different but euid/suid is equivalent
| > | as per the check in check_kill_permission().
| > |
| > | This patch removes cap_task_kill().
| >
| > 2.6.24 seems to have the same bug, what about a rediff for it and
| > submit the patch to -stable team?
|
| Luiz, could you confirm that the below works?
Yes, it does.
Thanks.
--
Luiz Fernando N. Capitulino
It works here against 2.6.24.3.
Originaly it was a fix - if I recall correctly - to allow a self
started X to kill completly. This works with the patch.
Chris
On Fri, 29 Feb 2008 15:26:34 -0600
[email protected] wrote:
> Quoting Luiz Fernando N. Capitulino ([email protected]):
> > Em Thu, 28 Feb 2008 11:38:17 -0600
> > [email protected] escreveu:
> >
> > | The original justification for cap_task_kill() was as follows:
> > |
> > | check_kill_permission() does appropriate uid equivalence checks.
> > | However with file capabilities it becomes possible for an
> > | unprivileged user to execute a file with file capabilities
> > | resulting in a more privileged task with the same uid.
> > |
> > | However now that cap_task_kill() always returns 0 (permission
> > | granted) when p->uid==current->uid, the whole hook is worthless,
> > | and only likely to create more subtle problems in the corner cases
> > | where it might still be called but return -EPERM. Those cases
> > | are basically when uids are different but euid/suid is equivalent
> > | as per the check in check_kill_permission().
> > |
> > | This patch removes cap_task_kill().
> >
> > 2.6.24 seems to have the same bug, what about a rediff for it and
> > submit the patch to -stable team?
>
> Luiz, could you confirm that the below works?
>
> thanks,
> -serge
>
> From c77b7d418933c14707383f06a1da61169e84071b Mon Sep 17 00:00:00 2001
> From: Serge Hallyn <[email protected]>
> Date: Fri, 29 Feb 2008 15:14:57 +0000
> Subject: [PATCH 1/1] file capabilities: remove cap_task_kill()
>
> The original justification for cap_task_kill() was as follows:
>
> check_kill_permission() does appropriate uid equivalence checks.
> However with file capabilities it becomes possible for an
> unprivileged user to execute a file with file capabilities
> resulting in a more privileged task with the same uid.
>
> However now that cap_task_kill() always returns 0 (permission
> granted) when p->uid==current->uid, the whole hook is worthless,
> and only likely to create more subtle problems in the corner cases
> where it might still be called but return -EPERM. Those cases
> are basically when uids are different but euid/suid is equivalent
> as per the check in check_kill_permission().
>
> This patch removes cap_task_kill().
>
> Signed-off-by: Serge Hallyn <[email protected]>
> ---
> include/linux/security.h | 3 +--
> security/capability.c | 1 -
> security/commoncap.c | 39 ---------------------------------------
> 3 files changed, 1 insertions(+), 42 deletions(-)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index ac05083..d842ee3 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -62,7 +62,6 @@ extern int cap_inode_need_killpriv(struct dentry *dentry);
> extern int cap_inode_killpriv(struct dentry *dentry);
> extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags);
> extern void cap_task_reparent_to_init (struct task_struct *p);
> -extern int cap_task_kill(struct task_struct *p, struct siginfo *info, int sig, u32 secid);
> extern int cap_task_setscheduler (struct task_struct *p, int policy, struct sched_param *lp);
> extern int cap_task_setioprio (struct task_struct *p, int ioprio);
> extern int cap_task_setnice (struct task_struct *p, int nice);
> @@ -2112,7 +2111,7 @@ static inline int security_task_kill (struct task_struct *p,
> struct siginfo *info, int sig,
> u32 secid)
> {
> - return cap_task_kill(p, info, sig, secid);
> + return 0;
> }
>
> static inline int security_task_wait (struct task_struct *p)
> diff --git a/security/capability.c b/security/capability.c
> index 9e99f36..2c6e06d 100644
> --- a/security/capability.c
> +++ b/security/capability.c
> @@ -40,7 +40,6 @@ static struct security_operations capability_ops = {
> .inode_need_killpriv = cap_inode_need_killpriv,
> .inode_killpriv = cap_inode_killpriv,
>
> - .task_kill = cap_task_kill,
> .task_setscheduler = cap_task_setscheduler,
> .task_setioprio = cap_task_setioprio,
> .task_setnice = cap_task_setnice,
> diff --git a/security/commoncap.c b/security/commoncap.c
> index ea61bc7..6e9065c 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -527,40 +527,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
> return cap_safe_nice(p);
> }
>
> -int cap_task_kill(struct task_struct *p, struct siginfo *info,
> - int sig, u32 secid)
> -{
> - if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info)))
> - return 0;
> -
> - /*
> - * Running a setuid root program raises your capabilities.
> - * Killing your own setuid root processes was previously
> - * allowed.
> - * We must preserve legacy signal behavior in this case.
> - */
> - if (p->euid == 0 && p->uid == current->uid)
> - return 0;
> -
> - /* sigcont is permitted within same session */
> - if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p)))
> - return 0;
> -
> - if (secid)
> - /*
> - * Signal sent as a particular user.
> - * Capabilities are ignored. May be wrong, but it's the
> - * only thing we can do at the moment.
> - * Used only by usb drivers?
> - */
> - return 0;
> - if (cap_issubset(p->cap_permitted, current->cap_permitted))
> - return 0;
> - if (capable(CAP_KILL))
> - return 0;
> -
> - return -EPERM;
> -}
> #else
> int cap_task_setscheduler (struct task_struct *p, int policy,
> struct sched_param *lp)
> @@ -575,11 +541,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
> {
> return 0;
> }
> -int cap_task_kill(struct task_struct *p, struct siginfo *info,
> - int sig, u32 secid)
> -{
> - return 0;
> -}
> #endif
>
> void cap_task_reparent_to_init (struct task_struct *p)
> --
> 1.5.2.5
>
> --
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>
--------------------
Chris Friedhoff
[email protected]