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>
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fd33c43677
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6d6f332842
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@ -822,15 +822,20 @@ int cap_task_setnice(struct task_struct *p, int nice)
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* Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
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* Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
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* the current task's bounding set. Returns 0 on success, -ve on error.
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* the current task's bounding set. Returns 0 on success, -ve on error.
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*/
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*/
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static long cap_prctl_drop(struct cred *new, unsigned long cap)
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static int cap_prctl_drop(unsigned long cap)
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{
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{
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struct cred *new;
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if (!ns_capable(current_user_ns(), CAP_SETPCAP))
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if (!ns_capable(current_user_ns(), CAP_SETPCAP))
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return -EPERM;
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return -EPERM;
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if (!cap_valid(cap))
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if (!cap_valid(cap))
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return -EINVAL;
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return -EINVAL;
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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cap_lower(new->cap_bset, cap);
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cap_lower(new->cap_bset, cap);
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return 0;
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return commit_creds(new);
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}
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}
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/**
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/**
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@ -848,26 +853,17 @@ static long cap_prctl_drop(struct cred *new, unsigned long cap)
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int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
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int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
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unsigned long arg4, unsigned long arg5)
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unsigned long arg4, unsigned long arg5)
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{
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{
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const struct cred *old = current_cred();
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struct cred *new;
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struct cred *new;
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long error = 0;
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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switch (option) {
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switch (option) {
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case PR_CAPBSET_READ:
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case PR_CAPBSET_READ:
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error = -EINVAL;
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if (!cap_valid(arg2))
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if (!cap_valid(arg2))
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goto error;
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return -EINVAL;
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error = !!cap_raised(new->cap_bset, arg2);
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return !!cap_raised(old->cap_bset, arg2);
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goto no_change;
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case PR_CAPBSET_DROP:
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case PR_CAPBSET_DROP:
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error = cap_prctl_drop(new, arg2);
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return cap_prctl_drop(arg2);
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if (error < 0)
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goto error;
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goto changed;
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/*
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/*
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* The next four prctl's remain to assist with transitioning a
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* The next four prctl's remain to assist with transitioning a
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@ -889,10 +885,9 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
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* capability-based-privilege environment.
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* capability-based-privilege environment.
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*/
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*/
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case PR_SET_SECUREBITS:
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case PR_SET_SECUREBITS:
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error = -EPERM;
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if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
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if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
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& (old->securebits ^ arg2)) /*[1]*/
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& (new->securebits ^ arg2)) /*[1]*/
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|| ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
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|| ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
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|| (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
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|| (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
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|| (cap_capable(current_cred(),
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|| (cap_capable(current_cred(),
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current_cred()->user_ns, CAP_SETPCAP,
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current_cred()->user_ns, CAP_SETPCAP,
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@ -906,46 +901,39 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
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*/
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*/
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)
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)
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/* cannot change a locked bit */
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/* cannot change a locked bit */
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goto error;
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return -EPERM;
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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new->securebits = arg2;
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new->securebits = arg2;
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goto changed;
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return commit_creds(new);
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case PR_GET_SECUREBITS:
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case PR_GET_SECUREBITS:
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error = new->securebits;
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return old->securebits;
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goto no_change;
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case PR_GET_KEEPCAPS:
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case PR_GET_KEEPCAPS:
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if (issecure(SECURE_KEEP_CAPS))
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return !!issecure(SECURE_KEEP_CAPS);
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error = 1;
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goto no_change;
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case PR_SET_KEEPCAPS:
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case PR_SET_KEEPCAPS:
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error = -EINVAL;
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if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
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if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
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goto error;
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return -EINVAL;
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error = -EPERM;
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if (issecure(SECURE_KEEP_CAPS_LOCKED))
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if (issecure(SECURE_KEEP_CAPS_LOCKED))
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goto error;
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return -EPERM;
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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if (arg2)
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if (arg2)
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new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
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new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
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else
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else
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new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
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new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
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goto changed;
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return commit_creds(new);
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default:
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default:
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/* No functionality available - continue with default */
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/* No functionality available - continue with default */
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error = -ENOSYS;
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return -ENOSYS;
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goto error;
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}
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}
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/* Functionality provided */
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changed:
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return commit_creds(new);
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no_change:
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error:
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abort_creds(new);
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return error;
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}
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}
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/**
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/**
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