linux-kernel - [for-linus][PATCH 2/7] tracing: Fix memory leak in eprobe

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Date:   Fri, 15 Oct 2021 23:02:24 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>
Subject: [for-linus][PATCH 2/7] tracing: Fix memory leak in eprobe_register()

From: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>

kmemleak report:
unreferenced object 0xffff900a70ec7ec0 (size 32):
  comm "ftracetest", pid 2770, jiffies 4295042510 (age 311.464s)
  hex dump (first 32 bytes):
    c8 31 23 45 0a 90 ff ff 40 85 c7 6e 0a 90 ff ff  .1#E....@.......
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<000000009d3751fd>] kmem_cache_alloc_trace+0x2a2/0x440
    [<0000000088b8124b>] eprobe_register+0x1e3/0x350
    [<000000002a9a0517>] __ftrace_event_enable_disable+0x7c/0x240
    [<0000000019109321>] event_enable_write+0x93/0xe0
    [<000000007d85b320>] vfs_write+0xb9/0x260
    [<00000000b94c5e41>] ksys_write+0x67/0xe0
    [<000000005a08c81d>] __x64_sys_write+0x1a/0x20
    [<00000000240bf576>] do_syscall_64+0x3b/0xc0
    [<0000000043d5d9f6>] entry_SYSCALL_64_after_hwframe+0x44/0xae

unreferenced object 0xffff900a56bbf280 (size 128):
  comm "ftracetest", pid 2770, jiffies 4295042510 (age 311.464s)
  hex dump (first 32 bytes):
    ff ff ff ff ff ff ff ff 00 00 00 00 01 00 00 00  ................
    80 69 3b b2 ff ff ff ff 20 69 3b b2 ff ff ff ff  .i;..... i;.....
  backtrace:
    [<000000009d3751fd>] kmem_cache_alloc_trace+0x2a2/0x440
    [<00000000c4e90fad>] eprobe_register+0x1fc/0x350
    [<000000002a9a0517>] __ftrace_event_enable_disable+0x7c/0x240
    [<0000000019109321>] event_enable_write+0x93/0xe0
    [<000000007d85b320>] vfs_write+0xb9/0x260
    [<00000000b94c5e41>] ksys_write+0x67/0xe0
    [<000000005a08c81d>] __x64_sys_write+0x1a/0x20
    [<00000000240bf576>] do_syscall_64+0x3b/0xc0
    [<0000000043d5d9f6>] entry_SYSCALL_64_after_hwframe+0x44/0xae

In new_eprobe_trigger(), allocated edata and trigger variables are
never freed.

To fix, free memory in disable_eprobe().

Link: https://lkml.kernel.org/r/20211008071802.GA2098@cosmos

Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events")
Signed-off-by: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/trace/trace_eprobe.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index 3044b762cbd7..570d081929fb 100644
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -632,6 +632,13 @@ static int disable_eprobe(struct trace_eprobe *ep,
 
 	trace_event_trigger_enable_disable(file, 0);
 	update_cond_flag(file);
+
+	/* Make sure nothing is using the edata or trigger */
+	tracepoint_synchronize_unregister();
+
+	kfree(edata);
+	kfree(trigger);
+
 	return 0;
 }
 
-- 
2.32.0