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| author | Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> | 2021-12-23 11:34:38 +0100 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2022-01-06 00:51:25 +0100 |
| commit | 823e670f7ed616d0ce993075c8afe0217885f79d (patch) | |
| tree | 82d1d3aaeb4fc7b68c19136fd458be2e269a48ac /kernel | |
| parent | ftrace/samples: Add missing prototypes direct functions (diff) | |
| download | linux-823e670f7ed616d0ce993075c8afe0217885f79d.tar.xz linux-823e670f7ed616d0ce993075c8afe0217885f79d.zip | |
tracing: Fix check for trace_percpu_buffer validity in get_trace_buf()
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.
Link: https://lkml.kernel.org/r/a920e4272e0b0635cf20c444707cbce1b2c8973d.1640255304.git.naveen.n.rao@linux.vnet.ibm.com
Cc: stable@vger.kernel.org
Fixes: e2ace001176dc9 ("tracing: Choose static tp_printk buffer by explicit nesting count")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/trace.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 88de94da596b..e1f55851e53f 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++; |