[PATCH v4 13/15] tracing/filters: Fix error positions for CPUS mask parsing

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

In parse_pred(), CPUS mask error paths report incorrect error positions:
- Checking 'str[i++] != '\'{'\'' post-increments 'i' before calling
  parse_error(), shifting the error caret one character past the
  missing brace position.
- In the CPUS operator check and comparison function selection check,
  'pos + i' points to the CPUS operand or past it instead of the
  unsupported operator.

Check 'str[i] != '\'{'\'' before incrementing 'i', and pass 'pos + op_pos'
for the operator checks so the error caret points accurately.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v4:
 - Drop Fixes and Cc: stable tags since these error position fixes are
   cleanups.
Changes in v3:
 - Group error position fixes for CPUS mask parsing into a single patch
   targeting commit 39f7c41c908b and commit 3cbec9d7b93d.
---
 kernel/trace/trace_events_filter.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 9b1100769676..1a9a1cc8daa2 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1932,16 +1932,17 @@ static int parse_pred(const char *str, void *data,
 		case OP_BAND:
 			break;
 		default:
-			parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i);
+			parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + op_pos);
 			goto err_free;
 		}
 
 		/* Skip CPUS */
 		i += 4;
-		if (str[i++] != '{') {
+		if (str[i] != '{') {
 			parse_error(pe, FILT_ERR_MISSING_BRACE_OPEN, pos + i);
 			goto err_free;
 		}
+		i++;
 		maskstart = i;
 
 		/* Walk the cpulist until closing } */
@@ -2029,7 +2030,7 @@ static int parse_pred(const char *str, void *data,
 			}
 		}
 		if (pred->fn_num == FILTER_PRED_FN_NOP) {
-			parse_error(pe, FILT_ERR_INVALID_OP, pos + i);
+			parse_error(pe, FILT_ERR_INVALID_OP, pos + op_pos);
 			goto err_free;
 		}