[PATCH] spmi: trace: fix stack-out-of-bound access in SPMI tracing functions

[David Collins]

trace_spmi_write_begin() and trace_spmi_read_end() both call
memcpy() with a length of "len + 1".  This leads to one extra
byte being read beyond the end of the specified buffer.  Fix
this out-of-bound memory access by using a length of "len"
instead.

Here is a KASAN log showing the issue:

BUG: KASAN: stack-out-of-bounds in trace_event_raw_event_spmi_read_end+0x1d0/0x234
Read of size 2 at addr ffffffc0265b7540 by task thermal@2.0-ser/1314
...
Call trace:
 dump_backtrace+0x0/0x3e8
 show_stack+0x2c/0x3c
 dump_stack_lvl+0xdc/0x11c
 print_address_description+0x74/0x384
 kasan_report+0x188/0x268
 kasan_check_range+0x270/0x2b0
 memcpy+0x90/0xe8
 trace_event_raw_event_spmi_read_end+0x1d0/0x234
 spmi_read_cmd+0x294/0x3ac
 spmi_ext_register_readl+0x84/0x9c
 regmap_spmi_ext_read+0x144/0x1b0 [regmap_spmi]
 _regmap_raw_read+0x40c/0x754
 regmap_raw_read+0x3a0/0x514
 regmap_bulk_read+0x418/0x494
 adc5_gen3_poll_wait_hs+0xe8/0x1e0 [qcom_spmi_adc5_gen3]
 ...
 __arm64_sys_read+0x4c/0x60
 invoke_syscall+0x80/0x218
 el0_svc_common+0xec/0x1c8
 ...

addr ffffffc0265b7540 is located in stack of task thermal@2.0-ser/1314 at offset 32 in frame:
 adc5_gen3_poll_wait_hs+0x0/0x1e0 [qcom_spmi_adc5_gen3]

this frame has 1 object:
 [32, 33) 'status'

Memory state around the buggy address:
 ffffffc0265b7400: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
 ffffffc0265b7480: 04 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffc0265b7500: 00 00 00 00 f1 f1 f1 f1 01 f3 f3 f3 00 00 00 00
                                           ^
 ffffffc0265b7580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffc0265b7600: f1 f1 f1 f1 01 f2 07 f2 f2 f2 01 f3 00 00 00 00
==================================================================

Fixes: a9fce374815d ("spmi: add command tracepoints for SPMI")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: David Collins <quic_collinsd@xxxxxxxxxxx>
---
 include/trace/events/spmi.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/trace/events/spmi.h b/include/trace/events/spmi.h
index 8b60efe18ba6..a6819fd85cdf 100644
--- a/include/trace/events/spmi.h
+++ b/include/trace/events/spmi.h
@@ -21,15 +21,15 @@ TRACE_EVENT(spmi_write_begin,
 		__field		( u8,         sid       )
 		__field		( u16,        addr      )
 		__field		( u8,         len       )
-		__dynamic_array	( u8,   buf,  len + 1   )
+		__dynamic_array	( u8,   buf,  len       )
 	),
 
 	TP_fast_assign(
 		__entry->opcode = opcode;
 		__entry->sid    = sid;
 		__entry->addr   = addr;
-		__entry->len    = len + 1;
-		memcpy(__get_dynamic_array(buf), buf, len + 1);
+		__entry->len    = len;
+		memcpy(__get_dynamic_array(buf), buf, len);
 	),
 
 	TP_printk("opc=%d sid=%02d addr=0x%04x len=%d buf=0x[%*phD]",
@@ -92,7 +92,7 @@ TRACE_EVENT(spmi_read_end,
 		__field		( u16,        addr      )
 		__field		( int,        ret       )
 		__field		( u8,         len       )
-		__dynamic_array	( u8,   buf,  len + 1   )
+		__dynamic_array	( u8,   buf,  len       )
 	),
 
 	TP_fast_assign(
@@ -100,8 +100,8 @@ TRACE_EVENT(spmi_read_end,
 		__entry->sid    = sid;
 		__entry->addr   = addr;
 		__entry->ret    = ret;
-		__entry->len    = len + 1;
-		memcpy(__get_dynamic_array(buf), buf, len + 1);
+		__entry->len    = len;
+		memcpy(__get_dynamic_array(buf), buf, len);
 	),
 
 	TP_printk("opc=%d sid=%02d addr=0x%04x ret=%d len=%02d buf=0x[%*phD]",
-- 
2.25.1