diff options
| author | David Hildenbrand <david@redhat.com> | 2020-11-11 15:53:16 +0100 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-11-19 16:56:58 +1100 |
| commit | d6718941a2767fb383e105d257d2105fe4f15f0e (patch) | |
| tree | 7a3a30e5af52d24cb847251a3fd9027d5d6b5d57 /arch/powerpc/platforms/powernv | |
| parent | c74cf7a3d59a21b290fe0468f5b470d0b8ee37df (diff) | |
| download | linux-d6718941a2767fb383e105d257d2105fe4f15f0e.tar.gz | |
powerpc/powernv/memtrace: Fix crashing the kernel when enabling concurrently
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+
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
Diffstat (limited to 'arch/powerpc/platforms/powernv')
| -rw-r--r-- | arch/powerpc/platforms/powernv/memtrace.c | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c index eea1f94482ff..0e42fe2d7b6a 100644 --- a/arch/powerpc/platforms/powernv/memtrace.c +++ b/arch/powerpc/platforms/powernv/memtrace.c @@ -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) |