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https://github.com/Divested-Mobile/DivestOS-Build.git
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100 lines
3.2 KiB
Diff
100 lines
3.2 KiB
Diff
From 24a4020b992c7f3cd3320d574947c5a1f51f264d Mon Sep 17 00:00:00 2001
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Tue, 31 Jan 2017 15:24:03 +0100
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Subject: [PATCH] timerfd: Protect the might cancel mechanism proper
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commit 1e38da300e1e395a15048b0af1e5305bd91402f6 upstream.
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The handling of the might_cancel queueing is not properly protected, so
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parallel operations on the file descriptor can race with each other and
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lead to list corruptions or use after free.
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Protect the context for these operations with a seperate lock.
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The wait queue lock cannot be reused for this because that would create a
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lock inversion scenario vs. the cancel lock. Replacing might_cancel with an
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atomic (atomic_t or atomic bit) does not help either because it still can
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race vs. the actual list operation.
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Bug: 36266767
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Reported-by: Dmitry Vyukov <dvyukov@google.com>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Cc: "linux-fsdevel@vger.kernel.org"
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Cc: syzkaller <syzkaller@googlegroups.com>
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Cc: Al Viro <viro@zeniv.linux.org.uk>
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Cc: linux-fsdevel@vger.kernel.org
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Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1701311521430.3457@nanos
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Signed-off-by: Siqi Lin <siqilin@google.com>
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Change-Id: I122753e0920e51757d3012cd1a133e823719be51
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---
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fs/timerfd.c | 17 ++++++++++++++---
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1 file changed, 14 insertions(+), 3 deletions(-)
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diff --git a/fs/timerfd.c b/fs/timerfd.c
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index 86b32c3cb247f..31374ec8f9bd2 100644
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--- a/fs/timerfd.c
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+++ b/fs/timerfd.c
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@@ -40,6 +40,7 @@ struct timerfd_ctx {
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short unsigned settime_flags; /* to show in fdinfo */
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struct rcu_head rcu;
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struct list_head clist;
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+ spinlock_t cancel_lock;
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bool might_cancel;
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};
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@@ -113,7 +114,7 @@ void timerfd_clock_was_set(void)
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rcu_read_unlock();
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}
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-static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
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+static void __timerfd_remove_cancel(struct timerfd_ctx *ctx)
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{
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if (ctx->might_cancel) {
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ctx->might_cancel = false;
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@@ -123,6 +124,13 @@ static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
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}
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}
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+static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
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+{
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+ spin_lock(&ctx->cancel_lock);
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+ __timerfd_remove_cancel(ctx);
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+ spin_unlock(&ctx->cancel_lock);
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+}
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+
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static bool timerfd_canceled(struct timerfd_ctx *ctx)
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{
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if (!ctx->might_cancel || ctx->moffs.tv64 != KTIME_MAX)
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@@ -133,6 +141,7 @@ static bool timerfd_canceled(struct timerfd_ctx *ctx)
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static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
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{
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+ spin_lock(&ctx->cancel_lock);
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if ((ctx->clockid == CLOCK_REALTIME ||
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ctx->clockid == CLOCK_REALTIME_ALARM ||
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ctx->clockid == CLOCK_POWEROFF_ALARM) &&
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@@ -143,9 +152,10 @@ static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
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list_add_rcu(&ctx->clist, &cancel_list);
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spin_unlock(&cancel_lock);
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}
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- } else if (ctx->might_cancel) {
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- timerfd_remove_cancel(ctx);
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+ } else {
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+ __timerfd_remove_cancel(ctx);
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}
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+ spin_unlock(&ctx->cancel_lock);
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}
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static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
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@@ -397,6 +407,7 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
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return -ENOMEM;
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init_waitqueue_head(&ctx->wqh);
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+ spin_lock_init(&ctx->cancel_lock);
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ctx->clockid = clockid;
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if (isalarm(ctx)) {
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