linux-kernel - [PATCH v2] tracing: Fix uaf issue when open the hist or hist

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Date:   Wed, 13 Dec 2023 09:51:38 +0800
From:   Zheng Yejian <zhengyejian1@...wei.com>
To:     <rostedt@...dmis.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-trace-kernel@...r.kernel.org>,
        <mathieu.desnoyers@...icios.com>, <mhiramat@...nel.org>,
        <yeweihua4@...wei.com>, <zhengyejian1@...wei.com>
Subject: [PATCH v2] tracing: Fix uaf issue when open the hist or hist_debug file

KASAN report following issue. The root cause is when opening 'hist'
file of an instance and accessing 'trace_event_file' in hist_show(),
but 'trace_event_file' has been freed due to the instance being removed.
'hist_debug' file has the same problem. To fix it, call
tracing_{open,release}_file_tr() in file_operations callback to have
the ref count and avoid 'trace_event_file' being freed.

  BUG: KASAN: slab-use-after-free in hist_show+0x11e0/0x1278
  Read of size 8 at addr ffff242541e336b8 by task head/190

  CPU: 4 PID: 190 Comm: head Not tainted 6.7.0-rc5-g26aff849438c #133
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   dump_backtrace+0x98/0xf8
   show_stack+0x1c/0x30
   dump_stack_lvl+0x44/0x58
   print_report+0xf0/0x5a0
   kasan_report+0x80/0xc0
   __asan_report_load8_noabort+0x1c/0x28
   hist_show+0x11e0/0x1278
   seq_read_iter+0x344/0xd78
   seq_read+0x128/0x1c0
   vfs_read+0x198/0x6c8
   ksys_read+0xf4/0x1e0
   __arm64_sys_read+0x70/0xa8
   invoke_syscall+0x70/0x260
   el0_svc_common.constprop.0+0xb0/0x280
   do_el0_svc+0x44/0x60
   el0_svc+0x34/0x68
   el0t_64_sync_handler+0xb8/0xc0
   el0t_64_sync+0x168/0x170

  Allocated by task 188:
   kasan_save_stack+0x28/0x50
   kasan_set_track+0x28/0x38
   kasan_save_alloc_info+0x20/0x30
   __kasan_slab_alloc+0x6c/0x80
   kmem_cache_alloc+0x15c/0x4a8
   trace_create_new_event+0x84/0x348
   __trace_add_new_event+0x18/0x88
   event_trace_add_tracer+0xc4/0x1a0
   trace_array_create_dir+0x6c/0x100
   trace_array_create+0x2e8/0x568
   instance_mkdir+0x48/0x80
   tracefs_syscall_mkdir+0x90/0xe8
   vfs_mkdir+0x3c4/0x610
   do_mkdirat+0x144/0x200
   __arm64_sys_mkdirat+0x8c/0xc0
   invoke_syscall+0x70/0x260
   el0_svc_common.constprop.0+0xb0/0x280
   do_el0_svc+0x44/0x60
   el0_svc+0x34/0x68
   el0t_64_sync_handler+0xb8/0xc0
   el0t_64_sync+0x168/0x170

  Freed by task 191:
   kasan_save_stack+0x28/0x50
   kasan_set_track+0x28/0x38
   kasan_save_free_info+0x34/0x58
   __kasan_slab_free+0xe4/0x158
   kmem_cache_free+0x19c/0x508
   event_file_put+0xa0/0x120
   remove_event_file_dir+0x180/0x320
   event_trace_del_tracer+0xb0/0x180
   __remove_instance+0x224/0x508
   instance_rmdir+0x44/0x78
   tracefs_syscall_rmdir+0xbc/0x140
   vfs_rmdir+0x1cc/0x4c8
   do_rmdir+0x220/0x2b8
   __arm64_sys_unlinkat+0xc0/0x100
   invoke_syscall+0x70/0x260
   el0_svc_common.constprop.0+0xb0/0x280
   do_el0_svc+0x44/0x60
   el0_svc+0x34/0x68
   el0t_64_sync_handler+0xb8/0xc0
   el0t_64_sync+0x168/0x170

Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
---
 kernel/trace/trace_events_hist.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

Steve, thanks for your review!

v2:
  - Introduce tracing_single_release_file_tr() to add the missing call for
    single_release() as suggested by Steve;
    Link: https://lore.kernel.org/all/20231212113546.6a51d359@gandalf.local.home/
  - Slightly modify the commit message and comments.

v1:
  Link: https://lore.kernel.org/all/20231212113317.4159890-1-zhengyejian1@huawei.com/

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 1abc07fba1b9..5296a08c0641 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -5619,14 +5619,22 @@ static int hist_show(struct seq_file *m, void *v)
 	return ret;
 }
 
+static int tracing_single_release_file_tr(struct inode *inode, struct file *filp)
+{
+	tracing_release_file_tr(inode, filp);
+	return single_release(inode, filp);
+}
+
 static int event_hist_open(struct inode *inode, struct file *file)
 {
 	int ret;
 
-	ret = security_locked_down(LOCKDOWN_TRACEFS);
+	ret = tracing_open_file_tr(inode, file);
 	if (ret)
 		return ret;
 
+	/* Clear private_data to avoid warning in single_open() */
+	file->private_data = NULL;
 	return single_open(file, hist_show, file);
 }
 
@@ -5634,7 +5642,7 @@ const struct file_operations event_hist_fops = {
 	.open = event_hist_open,
 	.read = seq_read,
 	.llseek = seq_lseek,
-	.release = single_release,
+	.release = tracing_single_release_file_tr,
 };
 
 #ifdef CONFIG_HIST_TRIGGERS_DEBUG
@@ -5900,10 +5908,12 @@ static int event_hist_debug_open(struct inode *inode, struct file *file)
 {
 	int ret;
 
-	ret = security_locked_down(LOCKDOWN_TRACEFS);
+	ret = tracing_open_file_tr(inode, file);
 	if (ret)
 		return ret;
 
+	/* Clear private_data to avoid warning in single_open() */
+	file->private_data = NULL;
 	return single_open(file, hist_debug_show, file);
 }
 
@@ -5911,7 +5921,7 @@ const struct file_operations event_hist_debug_fops = {
 	.open = event_hist_debug_open,
 	.read = seq_read,
 	.llseek = seq_lseek,
-	.release = single_release,
+	.release = tracing_single_release_file_tr,
 };
 #endif
 
-- 
2.25.1