The first patch fixes how we check for validity of trace_percpu_buffer,
fixing a kernel oops seen on ppc64le with the new osnoise tracer. The
second patch is new in v2 and carries the change to tag the pointer as a
percpu pointer.
v1:
http://lkml.kernel.org/r/[email protected]
- Naveen
Naveen N. Rao (2):
trace: Fix check for trace_percpu_buffer validity in get_trace_buf()
trace: Tag trace_percpu_buffer as a percpu pointer
kernel/trace/trace.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
base-commit: f7f0bb5eaecb1aff9cc8ab13425d43690b71ec44
--
2.34.1
Tag trace_percpu_buffer as a percpu pointer to resolve warnings
reported by sparse:
/linux/kernel/trace/trace.c:3218:46: warning: incorrect type in initializer (different address spaces)
/linux/kernel/trace/trace.c:3218:46: expected void const [noderef] __percpu *__vpp_verify
/linux/kernel/trace/trace.c:3218:46: got struct trace_buffer_struct *
/linux/kernel/trace/trace.c:3234:9: warning: incorrect type in initializer (different address spaces)
/linux/kernel/trace/trace.c:3234:9: expected void const [noderef] __percpu *__vpp_verify
/linux/kernel/trace/trace.c:3234:9: got int *
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Naveen N. Rao <[email protected]>
---
kernel/trace/trace.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e1f55851e53faa..78ea542ce3bc2e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3207,7 +3207,7 @@ struct trace_buffer_struct {
char buffer[4][TRACE_BUF_SIZE];
};
-static struct trace_buffer_struct *trace_percpu_buffer;
+static struct trace_buffer_struct __percpu *trace_percpu_buffer;
/*
* This allows for lockless recording. If we're nested too deeply, then
@@ -3236,7 +3236,7 @@ static void put_trace_buf(void)
static int alloc_percpu_trace_buffer(void)
{
- struct trace_buffer_struct *buffers;
+ struct trace_buffer_struct __percpu *buffers;
if (trace_percpu_buffer)
return 0;
--
2.34.1
With the new osnoise tracer, we are seeing the below splat:
Kernel attempted to read user page (c7d880000) - exploit attempt? (uid: 0)
BUG: Unable to handle kernel data access on read at 0xc7d880000
Faulting instruction address: 0xc0000000002ffa10
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
...
NIP [c0000000002ffa10] __trace_array_vprintk.part.0+0x70/0x2f0
LR [c0000000002ff9fc] __trace_array_vprintk.part.0+0x5c/0x2f0
Call Trace:
[c0000008bdd73b80] [c0000000001c49cc] put_prev_task_fair+0x3c/0x60 (unreliable)
[c0000008bdd73be0] [c000000000301430] trace_array_printk_buf+0x70/0x90
[c0000008bdd73c00] [c0000000003178b0] trace_sched_switch_callback+0x250/0x290
[c0000008bdd73c90] [c000000000e70d60] __schedule+0x410/0x710
[c0000008bdd73d40] [c000000000e710c0] schedule+0x60/0x130
[c0000008bdd73d70] [c000000000030614] interrupt_exit_user_prepare_main+0x264/0x270
[c0000008bdd73de0] [c000000000030a70] syscall_exit_prepare+0x150/0x180
[c0000008bdd73e10] [c00000000000c174] system_call_vectored_common+0xf4/0x278
osnoise tracer on ppc64le is triggering osnoise_taint() for negative
duration in get_int_safe_duration() called from
trace_sched_switch_callback()->thread_exit().
The problem though is that the check for a valid trace_percpu_buffer is
incorrect in get_trace_buf(). The check is being done after calculating
the pointer for the current cpu, rather than on the main percpu pointer.
Fix the check to be against trace_percpu_buffer.
Fixes: e2ace001176dc9 ("tracing: Choose static tp_printk buffer by explicit nesting count")
Cc: [email protected]
Signed-off-by: Naveen N. Rao <[email protected]>
---
kernel/trace/trace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 88de94da596b13..e1f55851e53faa 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3217,7 +3217,7 @@ static char *get_trace_buf(void)
{
struct trace_buffer_struct *buffer = this_cpu_ptr(trace_percpu_buffer);
- if (!buffer || buffer->nesting >= 4)
+ if (!trace_percpu_buffer || buffer->nesting >= 4)
return NULL;
buffer->nesting++;
--
2.34.1