[PATCH] perf/x86/rapl: Fix use-after-free on rapl_pmus_core on AMD/Hygon

[Jayapal Ashwin Nair]

The global rapl_pmus_core pointer can be used after it has been freed in
two ways:

1) init_rapl_pmus() stores the newly allocated rapl_pmus in
   *rapl_pmus_ptr before calling init_rapl_pmu(). If init_rapl_pmu()
   fails, rapl_pmus is freed but *rapl_pmus_ptr is not cleared, leaving
   rapl_pmus_core pointing to freed memory. rapl_pmu_init() then jumps
   to core_init_failed, where rapl_advertise() dereferences it.

2) If perf_pmu_register() fails for the power_core PMU,
   cleanup_rapl_pmus() frees rapl_pmus_core, but the pointer is not
   cleared. rapl_advertise() then dereferences the stale pointer in the
   same way as in 1).

In both cases, rmmod can result in use-after-free and a double free.

Fix this by setting rapl_pmus_core to NULL on both failure paths.

Fixes: b4943b8bfc41 ("perf/x86/rapl: Add core energy counter support for AMD CPUs")
Signed-off-by: Jayapal Ashwin Nair <jayapalashwin.nair@xxxxxxx>
---
 arch/x86/events/rapl.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
index 8ed03c32f560..b67986c58146 100644
--- a/arch/x86/events/rapl.c
+++ b/arch/x86/events/rapl.c
@@ -763,8 +763,10 @@ static int __init init_rapl_pmus(struct rapl_pmus **rapl_pmus_ptr, int rapl_pmu_
 	rapl_pmus->pmu.capabilities	= PERF_PMU_CAP_NO_EXCLUDE;
 
 	ret = init_rapl_pmu(rapl_pmus);
-	if (ret)
+	if (ret) {
+		*rapl_pmus_ptr = NULL;
 		kfree(rapl_pmus);
+	}
 
 	return ret;
 }
@@ -939,6 +941,7 @@ static int __init rapl_pmu_init(void)
 		if (ret) {
 			pr_warn("power-core PMU registration failed (%d)\n", ret);
 			cleanup_rapl_pmus(rapl_pmus_core);
+			rapl_pmus_core = NULL;
 		}
 	}
 
-- 
2.53.0