[PATCH] tracing/probe: Test nr_args match in looking for same probe events

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>

Testing triggered:

==================================================================
 BUG: KASAN: slab-out-of-bounds in trace_kprobe_create+0xa9e/0xe40
 Read of size 8 at addr ffff8880c4f25a48 by task ftracetest/4798

 CPU: 2 PID: 4798 Comm: ftracetest Not tainted 5.3.0-rc6-test+ #30
 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016
 Call Trace:
  dump_stack+0x7c/0xc0
  ? trace_kprobe_create+0xa9e/0xe40
  print_address_description+0x6c/0x332
  ? trace_kprobe_create+0xa9e/0xe40
  ? trace_kprobe_create+0xa9e/0xe40
  __kasan_report.cold.6+0x1a/0x3b
  ? trace_kprobe_create+0xa9e/0xe40
  kasan_report+0xe/0x12
  trace_kprobe_create+0xa9e/0xe40
  ? print_kprobe_event+0x280/0x280
  ? match_held_lock+0x1b/0x240
  ? find_held_lock+0xac/0xd0
  ? fs_reclaim_release.part.112+0x5/0x20
  ? lock_downgrade+0x350/0x350
  ? kasan_unpoison_shadow+0x30/0x40
  ? __kasan_kmalloc.constprop.6+0xc1/0xd0
  ? trace_kprobe_create+0xe40/0xe40
  ? trace_kprobe_create+0xe40/0xe40
  create_or_delete_trace_kprobe+0x2e/0x60
  trace_run_command+0xc3/0xe0
  ? trace_panic_handler+0x20/0x20
  ? kasan_unpoison_shadow+0x30/0x40
  trace_parse_run_command+0xdc/0x163
  vfs_write+0xe1/0x240
  ksys_write+0xba/0x150
  ? __ia32_sys_read+0x50/0x50
  ? tracer_hardirqs_on+0x61/0x180
  ? trace_hardirqs_off_caller+0x43/0x110
  ? mark_held_locks+0x29/0xa0
  ? do_syscall_64+0x14/0x260
  do_syscall_64+0x68/0x260

The cause was that the args array to compare between two probe events only
looked at one of the probe events size. If the other one had a smaller
number of args, it would read out of bounds memory.

Fixes: fe60b0ce8e733 ("tracing/probe: Reject exactly same probe event")
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_kprobe.c | 2 ++
 kernel/trace/trace_uprobe.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 402dc3ce88d3..d2543a403f25 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -537,6 +537,8 @@ static bool trace_kprobe_has_same_kprobe(struct trace_kprobe *orig,
 
 	list_for_each_entry(pos, &tpe->probes, list) {
 		orig = container_of(pos, struct trace_kprobe, tp);
+		if (orig->tp.nr_args != comp->tp.nr_args)
+			continue;
 		if (strcmp(trace_kprobe_symbol(orig),
 			   trace_kprobe_symbol(comp)) ||
 		    trace_kprobe_offset(orig) != trace_kprobe_offset(comp))
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index dd884341f5c5..11bcafdc93e2 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -420,6 +420,8 @@ static bool trace_uprobe_has_same_uprobe(struct trace_uprobe *orig,
 
 	list_for_each_entry(pos, &tpe->probes, list) {
 		orig = container_of(pos, struct trace_uprobe, tp);
+		if (orig->tp.nr_args != comp->tp.nr_args)
+			continue;
 		if (comp_inode != d_real_inode(orig->path.dentry) ||
 		    comp->offset != orig->offset)
 			continue;
-- 
2.20.1