[PATCH 6.18 012/430] perf/x86/amd: Check event before enable to avoid GPF

[Greg Kroah-Hartman]

6.18-stable review patch. If anyone has any objections, please let me know.

------------------

From: George Kennedy <george....@oracle.com>

[ Upstream commit 866cf36bfee4fba6a492d2dcc5133f857e3446b0 ]

On AMD machines cpuc->events[idx] can become NULL in a subtle race
condition with NMI->throttle->x86_pmu_stop().

Check event for NULL in amd_pmu_enable_all() before enable to avoid a GPF.
This appears to be an AMD only issue.

Syzkaller reported a GPF in amd_pmu_enable_all.

INFO: NMI handler (perf_event_nmi_handler) took too long to run: 13.143
msecs
Oops: general protection fault, probably for non-canonical address
0xdffffc0000000034: 0000 PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x00000000000001a0-0x00000000000001a7]
CPU: 0 UID: 0 PID: 328415 Comm: repro_36674776 Not tainted 6.12.0-rc1-syzk
RIP: 0010:x86_pmu_enable_event (arch/x86/events/perf_event.h:1195
arch/x86/events/core.c:1430)
RSP: 0018:ffff888118009d60 EFLAGS: 00010012
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000034 RSI: 0000000000000000 RDI: 00000000000001a0
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
R13: ffff88811802a440 R14: ffff88811802a240 R15: ffff8881132d8601
FS: 00007f097dfaa700(0000) GS:ffff888118000000(0000) GS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200001c0 CR3: 0000000103d56000 CR4: 00000000000006f0
Call Trace:
<IRQ>
amd_pmu_enable_all (arch/x86/events/amd/core.c:760 (discriminator 2))
x86_pmu_enable (arch/x86/events/core.c:1360)
event_sched_out (kernel/events/core.c:1191 kernel/events/core.c:1186
kernel/events/core.c:2346)
__perf_remove_from_context (kernel/events/core.c:2435)
event_function (kernel/events/core.c:259)
remote_function (kernel/events/core.c:92 (discriminator 1)
kernel/events/core.c:72 (discriminator 1))
__flush_smp_call_function_queue (./arch/x86/include/asm/jump_label.h:27
./include/linux/jump_label.h:207 ./include/trace/events/csd.h:64
kernel/smp.c:135 kernel/smp.c:540)
__sysvec_call_function_single (./arch/x86/include/asm/jump_label.h:27
./include/linux/jump_label.h:207
./arch/x86/include/asm/trace/irq_vectors.h:99 arch/x86/kernel/smp.c:272)
sysvec_call_function_single (arch/x86/kernel/smp.c:266 (discriminator 47)
arch/x86/kernel/smp.c:266 (discriminator 47))
</IRQ>

Reported-by: syzkaller <syzk...@googlegroups.com>
Signed-off-by: George Kennedy <george....@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
arch/x86/events/amd/core.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index b20661b8621d1..8868f5f5379ba 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -763,7 +763,12 @@ static void amd_pmu_enable_all(int added)
if (!test_bit(idx, cpuc->active_mask))
continue;

- amd_pmu_enable_event(cpuc->events[idx]);
+ /*
+ * FIXME: cpuc->events[idx] can become NULL in a subtle race
+ * condition with NMI->throttle->x86_pmu_stop().
+ */
+ if (cpuc->events[idx])
+ amd_pmu_enable_event(cpuc->events[idx]);
}
}

--
2.51.0

[Greg Kroah-Hartman]

6.12-stable review patch. If anyone has any objections, please let me know.

index b4a1a2576510e..36d28edf7a535 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -762,7 +762,12 @@ static void amd_pmu_enable_all(int added)

[Greg Kroah-Hartman]

6.6-stable review patch. If anyone has any objections, please let me know.

index aa8fc2cf1bde7..211f429750f5f 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -745,7 +745,12 @@ static void amd_pmu_enable_all(int added)

[Greg Kroah-Hartman]

6.1-stable review patch. If anyone has any objections, please let me know.

index 1282f1a702139..5a6ef45dc9b68 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -731,7 +731,12 @@ static void amd_pmu_enable_all(int added)