mirror of
https://github.com/Divested-Mobile/DivestOS-Build.git
synced 2024-10-01 01:35:54 -04:00
96 lines
3.0 KiB
Diff
96 lines
3.0 KiB
Diff
From 1e38da300e1e395a15048b0af1e5305bd91402f6 Mon Sep 17 00:00:00 2001
|
|
From: Thomas Gleixner <tglx@linutronix.de>
|
|
Date: Tue, 31 Jan 2017 15:24:03 +0100
|
|
Subject: timerfd: Protect the might cancel mechanism proper
|
|
|
|
The handling of the might_cancel queueing is not properly protected, so
|
|
parallel operations on the file descriptor can race with each other and
|
|
lead to list corruptions or use after free.
|
|
|
|
Protect the context for these operations with a seperate lock.
|
|
|
|
The wait queue lock cannot be reused for this because that would create a
|
|
lock inversion scenario vs. the cancel lock. Replacing might_cancel with an
|
|
atomic (atomic_t or atomic bit) does not help either because it still can
|
|
race vs. the actual list operation.
|
|
|
|
Reported-by: Dmitry Vyukov <dvyukov@google.com>
|
|
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Cc: "linux-fsdevel@vger.kernel.org"
|
|
Cc: syzkaller <syzkaller@googlegroups.com>
|
|
Cc: Al Viro <viro@zeniv.linux.org.uk>
|
|
Cc: linux-fsdevel@vger.kernel.org
|
|
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1701311521430.3457@nanos
|
|
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
---
|
|
fs/timerfd.c | 17 ++++++++++++++---
|
|
1 file changed, 14 insertions(+), 3 deletions(-)
|
|
|
|
diff --git a/fs/timerfd.c b/fs/timerfd.c
|
|
index c173cc1..384fa75 100644
|
|
--- a/fs/timerfd.c
|
|
+++ b/fs/timerfd.c
|
|
@@ -40,6 +40,7 @@ struct timerfd_ctx {
|
|
short unsigned settime_flags; /* to show in fdinfo */
|
|
struct rcu_head rcu;
|
|
struct list_head clist;
|
|
+ spinlock_t cancel_lock;
|
|
bool might_cancel;
|
|
};
|
|
|
|
@@ -112,7 +113,7 @@ void timerfd_clock_was_set(void)
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
-static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
|
|
+static void __timerfd_remove_cancel(struct timerfd_ctx *ctx)
|
|
{
|
|
if (ctx->might_cancel) {
|
|
ctx->might_cancel = false;
|
|
@@ -122,6 +123,13 @@ static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
|
|
}
|
|
}
|
|
|
|
+static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
|
|
+{
|
|
+ spin_lock(&ctx->cancel_lock);
|
|
+ __timerfd_remove_cancel(ctx);
|
|
+ spin_unlock(&ctx->cancel_lock);
|
|
+}
|
|
+
|
|
static bool timerfd_canceled(struct timerfd_ctx *ctx)
|
|
{
|
|
if (!ctx->might_cancel || ctx->moffs != KTIME_MAX)
|
|
@@ -132,6 +140,7 @@ static bool timerfd_canceled(struct timerfd_ctx *ctx)
|
|
|
|
static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
|
|
{
|
|
+ spin_lock(&ctx->cancel_lock);
|
|
if ((ctx->clockid == CLOCK_REALTIME ||
|
|
ctx->clockid == CLOCK_REALTIME_ALARM) &&
|
|
(flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) {
|
|
@@ -141,9 +150,10 @@ static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
|
|
list_add_rcu(&ctx->clist, &cancel_list);
|
|
spin_unlock(&cancel_lock);
|
|
}
|
|
- } else if (ctx->might_cancel) {
|
|
- timerfd_remove_cancel(ctx);
|
|
+ } else {
|
|
+ __timerfd_remove_cancel(ctx);
|
|
}
|
|
+ spin_unlock(&ctx->cancel_lock);
|
|
}
|
|
|
|
static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
|
|
@@ -400,6 +410,7 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
|
|
return -ENOMEM;
|
|
|
|
init_waitqueue_head(&ctx->wqh);
|
|
+ spin_lock_init(&ctx->cancel_lock);
|
|
ctx->clockid = clockid;
|
|
|
|
if (isalarm(ctx))
|
|
--
|
|
cgit v1.1
|
|
|