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![Romain Perier](/assets/img/avatar_default.png)
The recent decoupling of pagefault disable and preempt disable added an
explicit preempt_disable/enable() pair to the futex_atomic_cmpxchg_inatomic()
implementation in asm-generic/futex.h. But it forgot to add preempt_enable()
calls to the error handling code pathes, which results in a preemption count
imbalance.
This is observable on boot when the test for atomic_cmpxchg() is calling
futex_atomic_cmpxchg_inatomic() on a NULL pointer.
Add the missing preempt_enable() calls to the error handling code pathes.
[ tglx: Massaged changelog ]
Fixes: d9b9ff8c18
("sched/preempt, futex: Disable preemption in UP futex_atomic_cmpxchg_inatomic() explicitly")
Signed-off-by: Romain Perier <romain.perier@free-electrons.com>
Cc: linux-arch@vger.kernel.org
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1460640963-690-1-git-send-email-romain.perier@free-electrons.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
178 lines
3.7 KiB
C
178 lines
3.7 KiB
C
#ifndef _ASM_GENERIC_FUTEX_H
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#define _ASM_GENERIC_FUTEX_H
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#include <linux/futex.h>
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#include <linux/uaccess.h>
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#include <asm/errno.h>
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#ifndef CONFIG_SMP
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/*
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* The following implementation only for uniprocessor machines.
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* It relies on preempt_disable() ensuring mutual exclusion.
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*
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*/
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/**
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* futex_atomic_op_inuser() - Atomic arithmetic operation with constant
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* argument and comparison of the previous
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* futex value with another constant.
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*
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* @encoded_op: encoded operation to execute
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* @uaddr: pointer to user space address
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*
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* Return:
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* 0 - On success
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* <0 - On error
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*/
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static inline int
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futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
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{
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int op = (encoded_op >> 28) & 7;
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int cmp = (encoded_op >> 24) & 15;
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int oparg = (encoded_op << 8) >> 20;
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int cmparg = (encoded_op << 20) >> 20;
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int oldval, ret;
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u32 tmp;
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if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
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oparg = 1 << oparg;
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preempt_disable();
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pagefault_disable();
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ret = -EFAULT;
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if (unlikely(get_user(oldval, uaddr) != 0))
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goto out_pagefault_enable;
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ret = 0;
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tmp = oldval;
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switch (op) {
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case FUTEX_OP_SET:
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tmp = oparg;
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break;
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case FUTEX_OP_ADD:
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tmp += oparg;
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break;
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case FUTEX_OP_OR:
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tmp |= oparg;
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break;
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case FUTEX_OP_ANDN:
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tmp &= ~oparg;
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break;
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case FUTEX_OP_XOR:
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tmp ^= oparg;
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break;
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default:
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ret = -ENOSYS;
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}
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if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
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ret = -EFAULT;
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out_pagefault_enable:
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pagefault_enable();
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preempt_enable();
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if (ret == 0) {
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switch (cmp) {
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case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
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case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
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case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
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case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
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case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
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case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
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default: ret = -ENOSYS;
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}
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}
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return ret;
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}
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/**
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* futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
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* uaddr with newval if the current value is
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* oldval.
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* @uval: pointer to store content of @uaddr
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* @uaddr: pointer to user space address
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* @oldval: old value
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* @newval: new value to store to @uaddr
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*
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* Return:
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* 0 - On success
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* <0 - On error
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*/
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static inline int
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futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
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u32 oldval, u32 newval)
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{
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u32 val;
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preempt_disable();
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if (unlikely(get_user(val, uaddr) != 0)) {
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preempt_enable();
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return -EFAULT;
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}
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if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
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preempt_enable();
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return -EFAULT;
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}
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*uval = val;
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preempt_enable();
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return 0;
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}
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#else
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static inline int
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futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
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{
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int op = (encoded_op >> 28) & 7;
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int cmp = (encoded_op >> 24) & 15;
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int oparg = (encoded_op << 8) >> 20;
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int cmparg = (encoded_op << 20) >> 20;
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int oldval = 0, ret;
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if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
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oparg = 1 << oparg;
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if (! access_ok (VERIFY_WRITE, uaddr, sizeof(u32)))
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return -EFAULT;
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pagefault_disable();
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switch (op) {
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case FUTEX_OP_SET:
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case FUTEX_OP_ADD:
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case FUTEX_OP_OR:
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case FUTEX_OP_ANDN:
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case FUTEX_OP_XOR:
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default:
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ret = -ENOSYS;
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}
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pagefault_enable();
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if (!ret) {
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switch (cmp) {
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case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
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case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
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case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
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case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
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case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
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case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
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default: ret = -ENOSYS;
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}
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}
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return ret;
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}
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static inline int
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futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
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u32 oldval, u32 newval)
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{
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return -ENOSYS;
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}
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#endif /* CONFIG_SMP */
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#endif
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