linux-kernel - [PATCH 5.7 463/477] tracing/probe: Fix memleak in fetch_op

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Date:   Tue, 23 Jun 2020 21:57:40 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>,
        Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 5.7 463/477] tracing/probe: Fix memleak in fetch_op_data operations

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

commit 3aa8fdc37d16735e8891035becf25b3857d3efe0 upstream.

kmemleak report:
    [<57dcc2ca>] __kmalloc_track_caller+0x139/0x2b0
    [<f1c45d0f>] kstrndup+0x37/0x80
    [<f9761eb0>] parse_probe_arg.isra.7+0x3cc/0x630
    [<055bf2ba>] traceprobe_parse_probe_arg+0x2f5/0x810
    [<655a7766>] trace_kprobe_create+0x2ca/0x950
    [<4fc6a02a>] create_or_delete_trace_kprobe+0xf/0x30
    [<6d1c8a52>] trace_run_command+0x67/0x80
    [<be812cc0>] trace_parse_run_command+0xa7/0x140
    [<aecfe401>] probes_write+0x10/0x20
    [<2027641c>] __vfs_write+0x30/0x1e0
    [<6a4aeee1>] vfs_write+0x96/0x1b0
    [<3517fb7d>] ksys_write+0x53/0xc0
    [<dad91db7>] __ia32_sys_write+0x15/0x20
    [<da347f64>] do_syscall_32_irqs_on+0x3d/0x260
    [<fd0b7e7d>] do_fast_syscall_32+0x39/0xb0
    [<ea5ae810>] entry_SYSENTER_32+0xaf/0x102

Post parse_probe_arg(), the FETCH_OP_DATA operation type is overwritten
to FETCH_OP_ST_STRING, as a result memory is never freed since
traceprobe_free_probe_arg() iterates only over SYMBOL and DATA op types

Setup fetch string operation correctly after fetch_op_data operation.

Link: https://lkml.kernel.org/r/20200615143034.GA1734@cosmos

Cc: stable@...r.kernel.org
Fixes: a42e3c4de964 ("tracing/probe: Add immediate string parameter support")
Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/trace/trace_probe.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -639,8 +639,8 @@ static int traceprobe_parse_probe_arg_bo
 			ret = -EINVAL;
 			goto fail;
 		}
-		if ((code->op == FETCH_OP_IMM || code->op == FETCH_OP_COMM) ||
-		     parg->count) {
+		if ((code->op == FETCH_OP_IMM || code->op == FETCH_OP_COMM ||
+		     code->op == FETCH_OP_DATA) || parg->count) {
 			/*
 			 * IMM, DATA and COMM is pointing actual address, those
 			 * must be kept, and if parg->count != 0, this is an