powerpc/powernv/memtrace: Fix crashing the kernel when enabling concurrently (d6718941) · Commits · 戴 / test

It's very easy to crash the kernel right now by simply trying to enable memtrace concurrently, hammering on the "enable" interface loop.sh: #!/bin/bash dmesg --console-off while true; do echo 0x40000000 > /sys/kernel/debug/powerpc/memtrace/enable done [root@localhost ~]# loop.sh & [root@localhost ~]# loop.sh & Resulting quickly in a kernel crash. Let's properly protect using a mutex. Fixes: ("powerpc/powernv: Enable removal of memory for in memory tracing") Cc: stable@vger.kernel.org# v4.14+ Signed-off-by:

David Hildenbrand <david@redhat.com> Reviewed-by:

Oscar Salvador <osalvador@suse.de> Signed-off-by:

Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20201111145322.15793-3-david@redhat.com

arch/powerpc/platforms/powernv/memtrace.c

+15 −7

Original line number	Diff line number	Diff line
		@@ -30,6 +30,7 @@ struct memtrace_entry {
		char name[16];
		};

		static DEFINE_MUTEX(memtrace_mutex);
		static u64 memtrace_size;

		static struct memtrace_entry *memtrace_array;
		@@ -279,6 +280,7 @@ static int memtrace_online(void)

		static int memtrace_enable_set(void *data, u64 val)
		{
		int rc = -EAGAIN;
		u64 bytes;

		/*
		@@ -291,25 +293,31 @@ static int memtrace_enable_set(void *data, u64 val)
		return -EINVAL;
		}

		mutex_lock(&memtrace_mutex);

		/* Re-add/online previously removed/offlined memory */
		if (memtrace_size) {
		if (memtrace_online())
		return -EAGAIN;
		goto out_unlock;
		}

		if (!val)
		return 0;
		if (!val) {
		rc = 0;
		goto out_unlock;
		}

		/* Offline and remove memory */
		if (memtrace_init_regions_runtime(val))
		return -EINVAL;
		goto out_unlock;

		if (memtrace_init_debugfs())
		return -EINVAL;
		goto out_unlock;

		memtrace_size = val;

		return 0;
		rc = 0;
		out_unlock:
		mutex_unlock(&memtrace_mutex);
		return rc;
		}

		static int memtrace_enable_get(void data, u64 val)

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