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Diffstat (limited to 'kernel/futex.c')
-rw-r--r--kernel/futex.c72
1 files changed, 51 insertions, 21 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index fe28dc282ea..ea87f4d2f45 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -55,7 +55,7 @@
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
-#include <linux/module.h>
+#include <linux/export.h>
#include <linux/magic.h>
#include <linux/pid.h>
#include <linux/nsproxy.h>
@@ -218,6 +218,8 @@ static void drop_futex_key_refs(union futex_key *key)
* @uaddr: virtual address of the futex
* @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
* @key: address where result is stored.
+ * @rw: mapping needs to be read/write (values: VERIFY_READ,
+ * VERIFY_WRITE)
*
* Returns a negative error code or 0
* The key words are stored in *key on success.
@@ -229,12 +231,12 @@ static void drop_futex_key_refs(union futex_key *key)
* lock_page() might sleep, the caller should not hold a spinlock.
*/
static int
-get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
+get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
{
unsigned long address = (unsigned long)uaddr;
struct mm_struct *mm = current->mm;
struct page *page, *page_head;
- int err;
+ int err, ro = 0;
/*
* The futex address must be "naturally" aligned.
@@ -262,8 +264,18 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
again:
err = get_user_pages_fast(address, 1, 1, &page);
+ /*
+ * If write access is not required (eg. FUTEX_WAIT), try
+ * and get read-only access.
+ */
+ if (err == -EFAULT && rw == VERIFY_READ) {
+ err = get_user_pages_fast(address, 1, 0, &page);
+ ro = 1;
+ }
if (err < 0)
return err;
+ else
+ err = 0;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
page_head = page;
@@ -305,6 +317,13 @@ again:
if (!page_head->mapping) {
unlock_page(page_head);
put_page(page_head);
+ /*
+ * ZERO_PAGE pages don't have a mapping. Avoid a busy loop
+ * trying to find one. RW mapping would have COW'd (and thus
+ * have a mapping) so this page is RO and won't ever change.
+ */
+ if ((page_head == ZERO_PAGE(address)))
+ return -EFAULT;
goto again;
}
@@ -316,6 +335,15 @@ again:
* the object not the particular process.
*/
if (PageAnon(page_head)) {
+ /*
+ * A RO anonymous page will never change and thus doesn't make
+ * sense for futex operations.
+ */
+ if (ro) {
+ err = -EFAULT;
+ goto out;
+ }
+
key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
key->private.mm = mm;
key->private.address = address;
@@ -327,9 +355,10 @@ again:
get_futex_key_refs(key);
+out:
unlock_page(page_head);
put_page(page_head);
- return 0;
+ return err;
}
static inline void put_futex_key(union futex_key *key)
@@ -355,8 +384,8 @@ static int fault_in_user_writeable(u32 __user *uaddr)
int ret;
down_read(&mm->mmap_sem);
- ret = get_user_pages(current, mm, (unsigned long)uaddr,
- 1, 1, 0, NULL, NULL);
+ ret = fixup_user_fault(current, mm, (unsigned long)uaddr,
+ FAULT_FLAG_WRITE);
up_read(&mm->mmap_sem);
return ret < 0 ? ret : 0;
@@ -825,7 +854,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
{
struct task_struct *new_owner;
struct futex_pi_state *pi_state = this->pi_state;
- u32 curval, newval;
+ u32 uninitialized_var(curval), newval;
if (!pi_state)
return -EINVAL;
@@ -887,7 +916,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
{
- u32 oldval;
+ u32 uninitialized_var(oldval);
/*
* There is no waiter, so we unlock the futex. The owner died
@@ -940,7 +969,7 @@ futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
if (!bitset)
return -EINVAL;
- ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_READ);
if (unlikely(ret != 0))
goto out;
@@ -986,10 +1015,10 @@ futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2,
int ret, op_ret;
retry:
- ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
+ ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
if (unlikely(ret != 0))
goto out;
- ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
if (unlikely(ret != 0))
goto out_put_key1;
@@ -1243,10 +1272,11 @@ retry:
pi_state = NULL;
}
- ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
+ ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
if (unlikely(ret != 0))
goto out;
- ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2,
+ requeue_pi ? VERIFY_WRITE : VERIFY_READ);
if (unlikely(ret != 0))
goto out_put_key1;
@@ -1546,7 +1576,7 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
struct futex_pi_state *pi_state = q->pi_state;
struct task_struct *oldowner = pi_state->owner;
- u32 uval, curval, newval;
+ u32 uval, uninitialized_var(curval), newval;
int ret;
/* Owner died? */
@@ -1763,7 +1793,7 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
*
* Returns:
* 0 - uaddr contains val and hb has been locked
- * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked
+ * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked
*/
static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
struct futex_q *q, struct futex_hash_bucket **hb)
@@ -1790,7 +1820,7 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
* while the syscall executes.
*/
retry:
- ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key);
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, VERIFY_READ);
if (unlikely(ret != 0))
return ret;
@@ -1941,7 +1971,7 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect,
}
retry:
- ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key);
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, VERIFY_WRITE);
if (unlikely(ret != 0))
goto out;
@@ -2060,7 +2090,7 @@ retry:
if ((uval & FUTEX_TID_MASK) != vpid)
return -EPERM;
- ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE);
if (unlikely(ret != 0))
goto out;
@@ -2249,7 +2279,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
debug_rt_mutex_init_waiter(&rt_waiter);
rt_waiter.task = NULL;
- ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
if (unlikely(ret != 0))
goto out;
@@ -2451,7 +2481,7 @@ err_unlock:
*/
int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
{
- u32 uval, nval, mval;
+ u32 uval, uninitialized_var(nval), mval;
retry:
if (get_user(uval, uaddr))
@@ -2697,7 +2727,7 @@ static int __init futex_init(void)
futex_cmpxchg_enabled = 1;
for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
- plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock);
+ plist_head_init(&futex_queues[i].chain);
spin_lock_init(&futex_queues[i].lock);
}
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-11-22 22:17:11 +0000