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tracing/probes: Fix MAX_TRACE_ARGS limit handling

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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: 035ba76014 ("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>
This commit is contained in:
Mikel Rychliski 2024-09-30 16:26:54 -04:00 committed by Masami Hiramatsu (Google)
parent aff1871bfc
commit 73f3508047
4 changed files with 19 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
kernel/trace/trace_eprobe.c
View File

@ -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)

6
kernel/trace/trace_fprobe.c
View File

@ -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);

6
kernel/trace/trace_kprobe.c
View File

@ -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);

4
kernel/trace/trace_uprobe.c
View File

@ -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,
};