Linus,
Daniel Jacobowitz noticed that sys_capget is not behaving properly when
called with pid of 0. It is supposed to return current capabilities,
not those of swapper. Also cleaned up some duplicate code from a merge
error. Patch is tested, please apply.
thanks,
-chris
--- 2.5.41/kernel/capability.c Sun Sep 15 12:19:29 2002
+++ 2.5.41-capget/kernel/capability.c Wed Oct 9 16:31:10 2002
@@ -33,7 +33,7 @@
int ret = 0;
pid_t pid;
__u32 version;
- task_t *target;
+ task_t *target = current;
struct __user_cap_data_struct data;
if (get_user(version, &header->version))
@@ -52,21 +52,20 @@
return -EINVAL;
spin_lock(&task_capability_lock);
- read_lock(&tasklist_lock);
- target = find_task_by_pid(pid);
- if (!target) {
- ret = -ESRCH;
- goto out;
+ if (pid && pid != current->pid) {
+ read_lock(&tasklist_lock);
+ target = find_task_by_pid(pid);
+ read_unlock(&tasklist_lock);
+ if (!target) {
+ ret = -ESRCH;
+ goto out;
+ }
}
- data.permitted = cap_t(target->cap_permitted);
- data.inheritable = cap_t(target->cap_inheritable);
- data.effective = cap_t(target->cap_effective);
ret = security_ops->capget(target, &data.effective, &data.inheritable, &data.permitted);
out:
- read_unlock(&tasklist_lock);
spin_unlock(&task_capability_lock);
if (!ret && copy_to_user(dataptr, &data, sizeof data))
--
Linux Security Modules http://lsm.immunix.org http://lsm.bkbits.net
On Wed, 9 Oct 2002, Chris Wright wrote:
>
> Daniel Jacobowitz noticed that sys_capget is not behaving properly when
> called with pid of 0. It is supposed to return current capabilities,
> not those of swapper. Also cleaned up some duplicate code from a merge
> error. Patch is tested, please apply.
This is not correct. You drop the tasklist_lock before you actually set
read the capabilities, which means that by the time you read them, the
task you looked up may not be there any more.
Linus
* Linus Torvalds ([email protected]) wrote:
> On Wed, 9 Oct 2002, Chris Wright wrote:
> >
> > Daniel Jacobowitz noticed that sys_capget is not behaving properly when
> > called with pid of 0. It is supposed to return current capabilities,
> > not those of swapper. Also cleaned up some duplicate code from a merge
> > error. Patch is tested, please apply.
>
> This is not correct. You drop the tasklist_lock before you actually set
> read the capabilities, which means that by the time you read them, the
> task you looked up may not be there any more.
Doh...feeling dumb...
The patch below fixes my oversight. The locking is left the way it was,
and just the pid 0 part is fixed as well as the duplicate code removed.
This still applies against bk-curr and I tested it on 2.5.41.
thanks,
-chris
--- 2.5.41/kernel/capability.c Sun Sep 15 12:19:29 2002
+++ 2.4.41-capget/kernel/capability.c Thu Oct 10 14:36:29 2002
@@ -33,7 +33,7 @@
int ret = 0;
pid_t pid;
__u32 version;
- task_t *target;
+ task_t *target = current;
struct __user_cap_data_struct data;
if (get_user(version, &header->version))
@@ -54,15 +54,14 @@
spin_lock(&task_capability_lock);
read_lock(&tasklist_lock);
- target = find_task_by_pid(pid);
- if (!target) {
- ret = -ESRCH;
- goto out;
+ if (pid && pid != current->pid) {
+ target = find_task_by_pid(pid);
+ if (!target) {
+ ret = -ESRCH;
+ goto out;
+ }
}
- data.permitted = cap_t(target->cap_permitted);
- data.inheritable = cap_t(target->cap_inheritable);
- data.effective = cap_t(target->cap_effective);
ret = security_ops->capget(target, &data.effective, &data.inheritable, &data.permitted);
out:
On Thu, 10 Oct 2002, Chris Wright wrote:
>
> The patch below fixes my oversight. The locking is left the way it was,
> and just the pid 0 part is fixed as well as the duplicate code removed.
All right, call me stupid, but twhere is the "duplication" in the code you
removed?
I see the "security/capability.c" thing, yes, but I also look at
"security/dummy.c", and it appears that at least for that case nobody
would ever initialize the capabilities that we return to user space at
all.
So there's a bug somewhere there, and removing the duplication makes
things worse (admittedly for a case which isn't enabled in the regular
kernel, but still..)
So I'd ask you to have patience with me, and send a third patch that gets
this thing right too..
Linus
On Fri, Oct 11, 2002 at 07:58:46PM -0700, Linus Torvalds wrote:
>
> On Thu, 10 Oct 2002, Chris Wright wrote:
> >
> > The patch below fixes my oversight. The locking is left the way it was,
> > and just the pid 0 part is fixed as well as the duplicate code removed.
>
> All right, call me stupid, but twhere is the "duplication" in the code you
> removed?
>
> I see the "security/capability.c" thing, yes, but I also look at
> "security/dummy.c", and it appears that at least for that case nobody
> would ever initialize the capabilities that we return to user space at
> all.
>
> So there's a bug somewhere there, and removing the duplication makes
> things worse (admittedly for a case which isn't enabled in the regular
> kernel, but still..)
>
> So I'd ask you to have patience with me, and send a third patch that gets
> this thing right too..
Since this is still broken a month later... I don't know what to do
about the "duplication" question, but I'll leave that to Chris. This
is the uncontroversial portion of Chris's patch; its affect is to
change my zsh shell prompt back to a '%' as I'd expect.
Linus, please apply.
[PATCH] sys_capget should use current if the pid argument is 0
===== kernel/capability.c 1.6 vs edited =====
--- 1.6/kernel/capability.c Sat Sep 14 09:18:49 2002
+++ edited/kernel/capability.c Tue Nov 19 16:10:59 2002
@@ -33,7 +33,7 @@
int ret = 0;
pid_t pid;
__u32 version;
- task_t *target;
+ task_t *target = current;
struct __user_cap_data_struct data;
if (get_user(version, &header->version))
@@ -54,10 +54,12 @@
spin_lock(&task_capability_lock);
read_lock(&tasklist_lock);
- target = find_task_by_pid(pid);
- if (!target) {
- ret = -ESRCH;
- goto out;
+ if (pid && pid != current->pid) {
+ target = find_task_by_pid(pid);
+ if (!target) {
+ ret = -ESRCH;
+ goto out;
+ }
}
data.permitted = cap_t(target->cap_permitted);
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer
* Daniel Jacobowitz ([email protected]) wrote:
> On Fri, Oct 11, 2002 at 07:58:46PM -0700, Linus Torvalds wrote:
> >
> > On Thu, 10 Oct 2002, Chris Wright wrote:
> > >
> > > The patch below fixes my oversight. The locking is left the way it was,
> > > and just the pid 0 part is fixed as well as the duplicate code removed.
> >
> > All right, call me stupid, but twhere is the "duplication" in the code you
> > removed?
> >
> > I see the "security/capability.c" thing, yes, but I also look at
> > "security/dummy.c", and it appears that at least for that case nobody
> > would ever initialize the capabilities that we return to user space at
> > all.
> >
> > So there's a bug somewhere there, and removing the duplication makes
> > things worse (admittedly for a case which isn't enabled in the regular
> > kernel, but still..)
> >
> > So I'd ask you to have patience with me, and send a third patch that gets
> > this thing right too..
>
> Since this is still broken a month later... I don't know what to do
> about the "duplication" question, but I'll leave that to Chris. This
> is the uncontroversial portion of Chris's patch; its affect is to
> change my zsh shell prompt back to a '%' as I'd expect.
Thanks Daniel. I've been using the patch below, which differs only
slightly from the one you posted (code style matches the same lookup in
sys_capset). I'll follow up with the patch that removes the duplicate
code.
[PATCH] sys_capget should use current if the pid argument is 0
===== kernel/capability.c 1.5 vs edited =====
--- 1.5/kernel/capability.c Sun Sep 15 12:19:29 2002
+++ edited/kernel/capability.c Tue Nov 19 15:57:15 2002
@@ -54,11 +54,14 @@
spin_lock(&task_capability_lock);
read_lock(&tasklist_lock);
- target = find_task_by_pid(pid);
- if (!target) {
- ret = -ESRCH;
- goto out;
- }
+ if (pid && pid != current->pid) {
+ target = find_task_by_pid(pid);
+ if (!target) {
+ ret = -ESRCH;
+ goto out;
+ }
+ } else
+ target = current;
data.permitted = cap_t(target->cap_permitted);
data.inheritable = cap_t(target->cap_inheritable);
* Chris Wright ([email protected]) wrote:
> I'll follow up with the patch that removes the duplicate code.
This patch, relative to the last patch in this thread, removes the
code from cap_sysget that fills out the capability set being returned
to userspace. The module handles this in a policy specific way. This
updates the dummy.c module to fill in return data according to superuser
policy, and also disables setting capabilities in superuser policy.
[PATCH] remove duplicated assignment from sys_capget.
===== kernel/capability.c 1.6 vs edited =====
--- 1.6/kernel/capability.c Tue Nov 19 15:57:15 2002
+++ edited/kernel/capability.c Tue Nov 19 15:59:38 2002
@@ -63,9 +63,6 @@
} else
target = current;
- data.permitted = cap_t(target->cap_permitted);
- data.inheritable = cap_t(target->cap_inheritable);
- data.effective = cap_t(target->cap_effective);
ret = security_ops->capget(target, &data.effective, &data.inheritable, &data.permitted);
out:
===== security/dummy.c 1.4 vs edited =====
--- 1.4/security/dummy.c Fri Oct 11 14:22:54 2002
+++ edited/security/dummy.c Tue Nov 19 14:58:11 2002
@@ -27,6 +27,17 @@
static int dummy_capget (struct task_struct *target, kernel_cap_t * effective,
kernel_cap_t * inheritable, kernel_cap_t * permitted)
{
+ *effective = *inheritable = *permitted = 0;
+ if (!issecure(SECURE_NOROOT)) {
+ if (target->euid == 0) {
+ *permitted |= (~0 & ~CAP_FS_MASK);
+ *effective |= (~0 & ~CAP_TO_MASK(CAP_SETPCAP) & ~CAP_FS_MASK);
+ }
+ if (target->fsuid == 0) {
+ *permitted |= CAP_FS_MASK;
+ *effective |= CAP_FS_MASK;
+ }
+ }
return 0;
}
@@ -35,7 +46,7 @@
kernel_cap_t * inheritable,
kernel_cap_t * permitted)
{
- return 0;
+ return -EPERM;
}
static void dummy_capset_set (struct task_struct *target,