BACKPORT: commoncap: don't alloc the credential unless needed in cap_task_prctl
In function cap_task_prctl(), we would allocate a credential
unconditionally and then check if we support the requested function.
If not we would release this credential with abort_creds() by using
RCU method. But on some archs such as powerpc, the sys_prctl is heavily
used to get/set the floating point exception mode. So the unnecessary
allocating/releasing of credential not only introduce runtime overhead
but also do cause OOM due to the RCU implementation.
This patch removes abort_creds() from cap_task_prctl() by calling
prepare_creds() only when we need to modify it.
Reported-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Paul Moore <paul@paul-moore.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.l.morris@oracle.com>
(cherry picked from commit 6d6f3328422a3bc56b0d8dd026a5de845d2abfa7)
Bug: 35074030
Test: Builds.
Change-Id: I6f8136b017fd0dcafbf82553e64fbf002a268f20
Signed-off-by: Jorge Lucangeli Obes <jorgelo@google.com>
diff --git a/security/commoncap.c b/security/commoncap.c
index cc79598..1741c37 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -878,15 +878,20 @@
* Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
* the current task's bounding set. Returns 0 on success, -ve on error.
*/
-static long cap_prctl_drop(struct cred *new, unsigned long cap)
+static int cap_prctl_drop(unsigned long cap)
{
- if (!capable(CAP_SETPCAP))
+ struct cred *new;
+
+ if (!ns_capable(current_user_ns(), CAP_SETPCAP))
return -EPERM;
if (!cap_valid(cap))
return -EINVAL;
+ new = prepare_creds();
+ if (!new)
+ return -ENOMEM;
cap_lower(new->cap_bset, cap);
- return 0;
+ return commit_creds(new);
}
/**
@@ -904,26 +909,17 @@
int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5)
{
+ const struct cred *old = current_cred();
struct cred *new;
- long error = 0;
-
- new = prepare_creds();
- if (!new)
- return -ENOMEM;
switch (option) {
case PR_CAPBSET_READ:
- error = -EINVAL;
if (!cap_valid(arg2))
- goto error;
- error = !!cap_raised(new->cap_bset, arg2);
- goto no_change;
+ return -EINVAL;
+ return !!cap_raised(old->cap_bset, arg2);
case PR_CAPBSET_DROP:
- error = cap_prctl_drop(new, arg2);
- if (error < 0)
- goto error;
- goto changed;
+ return cap_prctl_drop(arg2);
/*
* The next four prctl's remain to assist with transitioning a
@@ -945,10 +941,9 @@
* capability-based-privilege environment.
*/
case PR_SET_SECUREBITS:
- error = -EPERM;
- if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
- & (new->securebits ^ arg2)) /*[1]*/
- || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
+ if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
+ & (old->securebits ^ arg2)) /*[1]*/
+ || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
|| (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
|| (cap_capable(current_cred(),
current_cred()->user_ns, CAP_SETPCAP,
@@ -962,31 +957,34 @@
*/
)
/* cannot change a locked bit */
- goto error;
+ return -EPERM;
+
+ new = prepare_creds();
+ if (!new)
+ return -ENOMEM;
new->securebits = arg2;
- goto changed;
+ return commit_creds(new);
case PR_GET_SECUREBITS:
- error = new->securebits;
- goto no_change;
+ return old->securebits;
case PR_GET_KEEPCAPS:
- if (issecure(SECURE_KEEP_CAPS))
- error = 1;
- goto no_change;
+ return !!issecure(SECURE_KEEP_CAPS);
case PR_SET_KEEPCAPS:
- error = -EINVAL;
if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
- goto error;
- error = -EPERM;
+ return -EINVAL;
if (issecure(SECURE_KEEP_CAPS_LOCKED))
- goto error;
+ return -EPERM;
+
+ new = prepare_creds();
+ if (!new)
+ return -ENOMEM;
if (arg2)
new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
else
new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
- goto changed;
+ return commit_creds(new);
case PR_CAP_AMBIENT:
if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
@@ -1027,18 +1025,8 @@
default:
/* No functionality available - continue with default */
- error = -ENOSYS;
- goto error;
+ return -ENOSYS;
}
-
- /* Functionality provided */
-changed:
- return commit_creds(new);
-
-no_change:
-error:
- abort_creds(new);
- return error;
}
/**
