@@ -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)
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: 9d5171a8f248 ("powerpc/powernv: Enable removal of memory for in memory tracing") Cc: stable@vger.kernel.org# v4.14+ Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Rashmica Gupta <rashmica.g@gmail.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- arch/powerpc/platforms/powernv/memtrace.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-)