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: 035ba76014c0 ("tracing/probes: cleanup: Set trace_probe::nr_args at trace_probe_init")
Signed-off-by: Mikel Rychliski <mikel@mikelr.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index b0e0ec85912e98870bbe6b0e2563d58e3377a755..ebda68ee9abff9013580b2fcee0b55a405b60b57 100644 (file)
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -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)

diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index a079abd8955b56579b9ed0638357caed3efcdf41..c62d1629cffecd72f01b54f8586b7b02ed671a5d 100644 (file)
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -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);

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 61a6da808203e07328b9ec6e3d03fd1f286ae34a..263fac44d3ca32ad0aee21c7e65ac744f1034ca7 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -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);

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 13f9270ed5ab439564f7c30dd963c2ecd7816bdb..b30fc8fcd0956aa1ea638d8bb36169ecdae64d05 100644 (file)
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -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,
                };