Commit 73f35080 authored by Mikel Rychliski's avatar Mikel Rychliski Committed by Masami Hiramatsu (Google)
Browse files

tracing/probes: Fix MAX_TRACE_ARGS limit handling 

When creating a trace_probe we would set nr_args prior to truncating the
arguments to MAX_TRACE_ARGS. However, we would only initialize arguments
up to the limit.

This caused invalid memory access when attempting to set up probes with
more than 128 fetchargs.

  BUG: kernel NULL pointer dereference, address: 0000000000000020
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: Oops: 0000 [#1] PREEMPT SMP PTI
  CPU: 0 UID: 0 PID: 1769 Comm: cat Not tainted 6.11.0-rc7+ #8
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-1.fc39 04/01/2014
  RIP: 0010:__set_print_fmt+0x134/0x330

Resolve the issue by applying the MAX_TRACE_ARGS limit earlier. Return
an error when there are too many arguments instead of silently
truncating.

Link: https://lore.kernel.org/all/20240930202656.292869-1-mikel@mikelr.com/



Fixes: 035ba760 ("tracing/probes: cleanup: Set trace_probe::nr_args at trace_probe_init")
Signed-off-by: default avatarMikel Rychliski <mikel@mikelr.com>
Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
parent aff1871b

kernel/trace/trace_eprobe.c

+6 −1
Original line number Diff line number Diff line
@@ -912,6 +912,11 @@ static int __trace_eprobe_create(int argc, const char *argv[]) 
		}

	}



	if (argc - 2 > MAX_TRACE_ARGS) {

		ret = -E2BIG;

		goto error;

	}



	mutex_lock(&event_mutex);

	event_call = find_and_get_event(sys_name, sys_event);

	ep = alloc_event_probe(group, event, event_call, argc - 2);
@@ -937,7 +942,7 @@ static int __trace_eprobe_create(int argc, const char *argv[]) 


	argc -= 2; argv += 2;

	/* parse arguments */

	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {

	for (i = 0; i < argc; i++) {

		trace_probe_log_set_index(i + 2);

		ret = trace_eprobe_tp_update_arg(ep, argv, i);

		if (ret)

kernel/trace/trace_fprobe.c

+5 −1
Original line number Diff line number Diff line
@@ -1187,6 +1187,10 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
		argc = new_argc;

		argv = new_argv;

	}

	if (argc > MAX_TRACE_ARGS) {

		ret = -E2BIG;

		goto out;

	}



	ret = traceprobe_expand_dentry_args(argc, argv, &dbuf);

	if (ret)
@@ -1203,7 +1207,7 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
	}



	/* parse arguments */

	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {

	for (i = 0; i < argc; i++) {

		trace_probe_log_set_index(i + 2);

		ctx.offset = 0;

		ret = traceprobe_parse_probe_arg(&tf->tp, i, argv[i], &ctx);

kernel/trace/trace_kprobe.c

+5 −1
Original line number Diff line number Diff line
@@ -1013,6 +1013,10 @@ static int __trace_kprobe_create(int argc, const char *argv[]) 
		argc = new_argc;

		argv = new_argv;

	}

	if (argc > MAX_TRACE_ARGS) {

		ret = -E2BIG;

		goto out;

	}



	ret = traceprobe_expand_dentry_args(argc, argv, &dbuf);

	if (ret)
@@ -1029,7 +1033,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) 
	}



	/* parse arguments */

	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {

	for (i = 0; i < argc; i++) {

		trace_probe_log_set_index(i + 2);

		ctx.offset = 0;

		ret = traceprobe_parse_probe_arg(&tk->tp, i, argv[i], &ctx);

kernel/trace/trace_uprobe.c

+3 −1
Original line number Diff line number Diff line
@@ -565,6 +565,8 @@ static int __trace_uprobe_create(int argc, const char **argv) 


	if (argc < 2)

		return -ECANCELED;

	if (argc - 2 > MAX_TRACE_ARGS)

		return -E2BIG;



	if (argv[0][1] == ':')

		event = &argv[0][2];
@@ -690,7 +692,7 @@ static int __trace_uprobe_create(int argc, const char **argv) 
	tu->filename = filename;



	/* parse arguments */

	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {

	for (i = 0; i < argc; i++) {

		struct traceprobe_parse_context ctx = {

			.flags = (is_return ? TPARG_FL_RETURN : 0) | TPARG_FL_USER,

		};