[PATCH] tracing: Avoid memory leak in process_system_preds()

[PATCH] tracing: Avoid memory leak in process_system_preds()

[Keita Suzuki]

When failing in the allocation of filter_item, process_system_preds()
goes to fail_mem, where the allocated filter is freed.

However, this leads to memory leak of filter->filter_string and
filter->prog, which is allocated before and in process_preds().
This bug has been detected by kmemleak as well.

Fix this by changing kfree to __free_fiter.

unreferenced object 0xffff8880658007c0 (size 32):
  comm "bash", pid 579, jiffies 4295096372 (age 17.752s)
  hex dump (first 32 bytes):
    63 6f 6d 6d 6f 6e 5f 70 69 64 20 20 3e 20 31 30  common_pid  > 10
    00 00 00 00 00 00 00 00 65 73 00 00 00 00 00 00  ........es......
  backtrace:
    [<0000000067441602>] kstrdup+0x2d/0x60
    [<00000000141cf7b7>] apply_subsystem_event_filter+0x378/0x932
    [<000000009ca32334>] subsystem_filter_write+0x5a/0x90
    [<0000000072da2bee>] vfs_write+0xe1/0x240
    [<000000004f14f473>] ksys_write+0xb4/0x150
    [<00000000a968b4a0>] do_syscall_64+0x6d/0x1e0
    [<000000001a189f40>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
unreferenced object 0xffff888060c22d00 (size 64):
  comm "bash", pid 579, jiffies 4295096372 (age 17.752s)
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 00 e8 d7 41 80 88 ff ff  ...........A....
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000b8c1b109>] process_preds+0x243/0x1820
    [<000000003972c7f0>] apply_subsystem_event_filter+0x3be/0x932
    [<000000009ca32334>] subsystem_filter_write+0x5a/0x90
    [<0000000072da2bee>] vfs_write+0xe1/0x240
    [<000000004f14f473>] ksys_write+0xb4/0x150
    [<00000000a968b4a0>] do_syscall_64+0x6d/0x1e0
    [<000000001a189f40>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
unreferenced object 0xffff888041d7e800 (size 512):
  comm "bash", pid 579, jiffies 4295096372 (age 17.752s)
  hex dump (first 32 bytes):
    70 bc 85 97 ff ff ff ff 0a 00 00 00 00 00 00 00  p...............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<000000001e04af34>] process_preds+0x71a/0x1820
    [<000000003972c7f0>] apply_subsystem_event_filter+0x3be/0x932
    [<000000009ca32334>] subsystem_filter_write+0x5a/0x90
    [<0000000072da2bee>] vfs_write+0xe1/0x240
    [<000000004f14f473>] ksys_write+0xb4/0x150
    [<00000000a968b4a0>] do_syscall_64+0x6d/0x1e0
    [<000000001a189f40>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Signed-off-by: Keita Suzuki <keitasuzuki.park@sslab.ics.keio.ac.jp>
---
 kernel/trace/trace_events_filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index c9a74f82b14a..bf44f6bbd0c3 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1662,7 +1662,7 @@ static int process_system_preds(struct trace_subsystem_dir *dir,
 	parse_error(pe, FILT_ERR_BAD_SUBSYS_FILTER, 0);
 	return -EINVAL;
  fail_mem:
-	kfree(filter);
+	__free_filter(filter);
 	/* If any call succeeded, we still need to sync */
 	if (!fail)
 		tracepoint_synchronize_unregister();
-- 
2.17.1

Re: [PATCH] tracing: Avoid memory leak in process_system_preds()

[Steven Rostedt]

On Wed, 11 Dec 2019 09:12:58 +0000
Keita Suzuki <keitasuzuki.park@sslab.ics.keio.ac.jp> wrote:

> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -1662,7 +1662,7 @@ static int process_system_preds(struct trace_subsystem_dir *dir,
>  	parse_error(pe, FILT_ERR_BAD_SUBSYS_FILTER, 0);
>  	return -EINVAL;
>   fail_mem:
> -	kfree(filter);
> +	__free_filter(filter);
>  	/* If any call succeeded, we still need to sync */
>  	if (!fail)
>  		tracepoint_synchronize_unregister();

Applied. Thanks Keita!

-- Steve