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-rw-r--r--Documentation/fault-injection/fault-injection.txt11
-rw-r--r--kernel/futex.c89
-rw-r--r--lib/Kconfig.debug7
3 files changed, 105 insertions, 2 deletions
diff --git a/Documentation/fault-injection/fault-injection.txt b/Documentation/fault-injection/fault-injection.txt
index 4cf1a2a6bd72..415484f3d59a 100644
--- a/Documentation/fault-injection/fault-injection.txt
+++ b/Documentation/fault-injection/fault-injection.txt
@@ -15,6 +15,10 @@ o fail_page_alloc
injects page allocation failures. (alloc_pages(), get_free_pages(), ...)
+o fail_futex
+
+ injects futex deadlock and uaddr fault errors.
+
o fail_make_request
injects disk IO errors on devices permitted by setting
@@ -113,6 +117,12 @@ configuration of fault-injection capabilities.
specifies the minimum page allocation order to be injected
failures.
+- /sys/kernel/debug/fail_futex/ignore-private:
+
+ Format: { 'Y' | 'N' }
+ default is 'N', setting it to 'Y' will disable failure injections
+ when dealing with private (address space) futexes.
+
o Boot option
In order to inject faults while debugfs is not available (early boot time),
@@ -121,6 +131,7 @@ use the boot option:
failslab=
fail_page_alloc=
fail_make_request=
+ fail_futex=
mmc_core.fail_request=<interval>,<probability>,<space>,<times>
How to add new fault injection capability
diff --git a/kernel/futex.c b/kernel/futex.c
index 153eb22b0fc0..6ea31bb703c9 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -64,6 +64,7 @@
#include <linux/hugetlb.h>
#include <linux/freezer.h>
#include <linux/bootmem.h>
+#include <linux/fault-inject.h>
#include <asm/futex.h>
@@ -258,6 +259,66 @@ static unsigned long __read_mostly futex_hashsize;
static struct futex_hash_bucket *futex_queues;
+/*
+ * Fault injections for futexes.
+ */
+#ifdef CONFIG_FAIL_FUTEX
+
+static struct {
+ struct fault_attr attr;
+
+ u32 ignore_private;
+} fail_futex = {
+ .attr = FAULT_ATTR_INITIALIZER,
+ .ignore_private = 0,
+};
+
+static int __init setup_fail_futex(char *str)
+{
+ return setup_fault_attr(&fail_futex.attr, str);
+}
+__setup("fail_futex=", setup_fail_futex);
+
+bool should_fail_futex(bool fshared)
+{
+ if (fail_futex.ignore_private && !fshared)
+ return false;
+
+ return should_fail(&fail_futex.attr, 1);
+}
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+
+static int __init fail_futex_debugfs(void)
+{
+ umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
+ struct dentry *dir;
+
+ dir = fault_create_debugfs_attr("fail_futex", NULL,
+ &fail_futex.attr);
+ if (IS_ERR(dir))
+ return PTR_ERR(dir);
+
+ if (!debugfs_create_bool("ignore-private", mode, dir,
+ &fail_futex.ignore_private)) {
+ debugfs_remove_recursive(dir);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+late_initcall(fail_futex_debugfs);
+
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
+
+#else
+static inline bool should_fail_futex(bool fshared)
+{
+ return false;
+}
+#endif /* CONFIG_FAIL_FUTEX */
+
static inline void futex_get_mm(union futex_key *key)
{
atomic_inc(&key->private.mm->mm_count);
@@ -413,6 +474,9 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
if (unlikely(!access_ok(rw, uaddr, sizeof(u32))))
return -EFAULT;
+ if (unlikely(should_fail_futex(fshared)))
+ return -EFAULT;
+
/*
* PROCESS_PRIVATE futexes are fast.
* As the mm cannot disappear under us and the 'key' only needs
@@ -428,6 +492,10 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
}
again:
+ /* Ignore any VERIFY_READ mapping (futex common case) */
+ if (unlikely(should_fail_futex(fshared)))
+ return -EFAULT;
+
err = get_user_pages_fast(address, 1, 1, &page);
/*
* If write access is not required (eg. FUTEX_WAIT), try
@@ -516,7 +584,7 @@ again:
* A RO anonymous page will never change and thus doesn't make
* sense for futex operations.
*/
- if (ro) {
+ if (unlikely(should_fail_futex(fshared)) || ro) {
err = -EFAULT;
goto out;
}
@@ -974,6 +1042,9 @@ static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval)
{
u32 uninitialized_var(curval);
+ if (unlikely(should_fail_futex(true)))
+ return -EFAULT;
+
if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)))
return -EFAULT;
@@ -1015,12 +1086,18 @@ static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
if (get_futex_value_locked(&uval, uaddr))
return -EFAULT;
+ if (unlikely(should_fail_futex(true)))
+ return -EFAULT;
+
/*
* Detect deadlocks.
*/
if ((unlikely((uval & FUTEX_TID_MASK) == vpid)))
return -EDEADLK;
+ if ((unlikely(should_fail_futex(true))))
+ return -EDEADLK;
+
/*
* Lookup existing state first. If it exists, try to attach to
* its pi_state.
@@ -1155,6 +1232,9 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this,
*/
newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
+ if (unlikely(should_fail_futex(true)))
+ ret = -EFAULT;
+
if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
ret = -EFAULT;
else if (curval != uval)
@@ -1457,6 +1537,9 @@ static int futex_proxy_trylock_atomic(u32 __user *pifutex,
if (get_futex_value_locked(&curval, pifutex))
return -EFAULT;
+ if (unlikely(should_fail_futex(true)))
+ return -EFAULT;
+
/*
* Find the top_waiter and determine if there are additional waiters.
* If the caller intends to requeue more than 1 waiter to pifutex,
@@ -2537,7 +2620,7 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
* futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
* @uaddr: the futex we initially wait on (non-pi)
* @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be
- * the same type, no requeueing from private to shared, etc.
+ * the same type, no requeueing from private to shared, etc.
* @val: the expected value of uaddr
* @abs_time: absolute timeout
* @bitset: 32 bit wakeup bitset set by userspace, defaults to all
@@ -3012,6 +3095,8 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
cmd == FUTEX_WAIT_BITSET ||
cmd == FUTEX_WAIT_REQUEUE_PI)) {
+ if (unlikely(should_fail_futex(!(op & FUTEX_PRIVATE_FLAG))))
+ return -EFAULT;
if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
return -EFAULT;
if (!timespec_valid(&ts))
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e2894b23efb6..22554d6f720f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1542,6 +1542,13 @@ config FAIL_MMC_REQUEST
and to test how the mmc host driver handles retries from
the block device.
+config FAIL_FUTEX
+ bool "Fault-injection capability for futexes"
+ select DEBUG_FS
+ depends on FAULT_INJECTION && FUTEX
+ help
+ Provide fault-injection capability for futexes.
+
config FAULT_INJECTION_DEBUG_FS
bool "Debugfs entries for fault-injection capabilities"
depends on FAULT_INJECTION && SYSFS && DEBUG_FS