From c7bdb07902e0b633795372665d0154e7267ecd0e Mon Sep 17 00:00:00 2001 From: Beau Belgrave Date: Wed, 19 Apr 2023 14:41:40 -0700 Subject: [PATCH] tracing: Fix print_fields() for __dyn_loc/__rel_loc Both print_fields() and print_array() do not handle if dynamic data ends at the last byte of the payload for both __dyn_loc and __rel_loc field types. For __rel_loc, the offset was off by 4 bytes, leading to incorrect strings and data being printed out. In print_array() the buffer pos was missed from being advanced, which results in the first payload byte being used as the offset base instead of the field offset. Advance __rel_loc offset by 4 to ensure correct offset and advance pos to the field offset to ensure correct data is displayed when printing arrays. Change >= to > when checking if data is in-bounds, since it's valid for dynamic data to include the last byte of the payload. Example outputs for event format: field:unsigned short common_type; offset:0; size:2; signed:0; field:unsigned char common_flags; offset:2; size:1; signed:0; field:unsigned char common_preempt_count; offset:3; size:1; signed:0; field:int common_pid; offset:4; size:4; signed:1; field:__rel_loc char text[]; offset:8; size:4; signed:1; Output before: tp_rel_loc: text= Output after: tp_rel_loc: text=Test Link: https://lkml.kernel.org/r/20230419214140.4158-3-beaub@linux.microsoft.com Fixes: 80a76994b2d8 ("tracing: Add "fields" option to show raw trace event fields") Reported-by: Doug Cook Signed-off-by: Beau Belgrave Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace_output.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 780c6971c944..952cc8aa8e59 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -819,13 +819,15 @@ static void print_array(struct trace_iterator *iter, void *pos, len = *(int *)pos >> 16; if (field) - offset += field->offset; + offset += field->offset + sizeof(int); - if (offset + len >= iter->ent_size) { + if (offset + len > iter->ent_size) { trace_seq_puts(&iter->seq, ""); return; } + pos = (void *)iter->ent + offset; + for (i = 0; i < len; i++, pos++) { if (i) trace_seq_putc(&iter->seq, ','); @@ -861,9 +863,9 @@ static void print_fields(struct trace_iterator *iter, struct trace_event_call *c len = *(int *)pos >> 16; if (field->filter_type == FILTER_RDYN_STRING) - offset += field->offset; + offset += field->offset + sizeof(int); - if (offset + len >= iter->ent_size) { + if (offset + len > iter->ent_size) { trace_seq_puts(&iter->seq, ""); break; } -- 2.39.5