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authorTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>2014-07-22 21:20:01 +0900
committerJames Morris <james.l.morris@oracle.com>2014-07-24 21:12:30 +1000
commit6d6f3328422a3bc56b0d8dd026a5de845d2abfa7 (patch)
tree51c24037355a91d098568a88f7dd9715dee8008c /security/commoncap.c
parentfd33c43677a7965624b46352a686a7c1e72ae4aa (diff)
downloadlinux-6d6f3328422a3bc56b0d8dd026a5de845d2abfa7.tar.gz
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>
Diffstat (limited to 'security/commoncap.c')
-rw-r--r--security/commoncap.c72
1 files changed, 30 insertions, 42 deletions
diff --git a/security/commoncap.c b/security/commoncap.c
index b9d613e0ef14..9fe46e22c7f2 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -822,15 +822,20 @@ int cap_task_setnice(struct task_struct *p, int nice)
* 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)
{
+ 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);
}
/**
@@ -848,26 +853,17 @@ static long cap_prctl_drop(struct cred *new, unsigned long cap)
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
@@ -889,10 +885,9 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
* 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,
@@ -906,46 +901,39 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
*/
)
/* 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);
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;
}
/**