tracing: Remove precision vsnprintf() check from print event

This reverts 60be76eeabb3d ("tracing: Add size check when printing
trace_marker output"). The only reason the precision check was added
was because of a bug that miscalculated the write size of the string into
the ring buffer and it truncated it removing the terminating nul byte. On
reading the trace it crashed the kernel. But this was due to the bug in
the code that happened during development and should never happen in
practice. If anything, the precision can hide bugs where the string in the
ring buffer isn't nul terminated and it will not be checked.

Link: https://lore.kernel.org/all/C7E7AF1A-D30F-4D18-B8E5-AF1EF58004F5@linux.ibm.com/
Link: https://lore.kernel.org/linux-trace-kernel/20240227125706.04279ac2@gandalf.local.home
Link: https://lore.kernel.org/all/20240302111244.3a1674be@gandalf.local.home/
Link: https://lore.kernel.org/linux-trace-kernel/20240304174341.2a561d9f@gandalf.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: 60be76eeabb3d ("tracing: Add size check when printing trace_marker output")
Reported-by: Sachin Sant <sachinp@linux.ibm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 3e7fa44dc2b24850f8b836f6bd223807fbcf0c48..d8b302d0108302d9ef2debe735c4b7778a217f90 100644 (file)
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1587,12 +1587,11 @@ static enum print_line_t trace_print_print(struct trace_iterator *iter,
 {
        struct print_entry *field;
        struct trace_seq *s = &iter->seq;
-       int max = iter->ent_size - offsetof(struct print_entry, buf);
 
        trace_assign_type(field, iter->ent);
 
        seq_print_ip_sym(s, field->ip, flags);
-       trace_seq_printf(s, ": %.*s", max, field->buf);
+       trace_seq_printf(s, ": %s", field->buf);
 
        return trace_handle_return(s);
 }
@@ -1601,11 +1600,10 @@ static enum print_line_t trace_print_raw(struct trace_iterator *iter, int flags,
                                         struct trace_event *event)
 {
        struct print_entry *field;
-       int max = iter->ent_size - offsetof(struct print_entry, buf);
 
        trace_assign_type(field, iter->ent);
 
-       trace_seq_printf(&iter->seq, "# %lx %.*s", field->ip, max, field->buf);
+       trace_seq_printf(&iter->seq, "# %lx %s", field->ip, field->buf);
 
        return trace_handle_return(&iter->seq);
 }