[PATCH] kprobe : fix out-of-bounds in register_kretprobe when parsing negative data_size

[Cheng Jian]

When we register kretprobe, data_size used to allocate space
for storing per-instance private data.

If we use a negative values as data_size, It will register
successfully, then cause slab-out-of-bounds which can be
found by KASAN.

The call trace is like :

	=============================================================
	BUG: KASAN: slab-out-of-bounds in trampoline_probe_handler
	+0xb4/0x2f0 at addr ffff8000b732a7a0
	Read of size 8 by task sh/1945
	=============================================================
	BUG kmalloc-64 (Tainted: G    B   W  OE  ):
	kasan: bad access detected
	-------------------------------------------------------------
	INFO: Allocated in register_kretprobe+0x12c/0x350
	age=157 cpu=4 pid=1947
	......
	INFO: Freed in do_one_initcall+0x110/0x260
	age=169 cpu=4 pid=1947
	......
	INFO: Slab 0xffff7bffc2dcca80 objects=21 used=10
	fp=0xffff8000b732aa80 flags=0x7fff00000004080
	INFO: Object 0xffff8000b732a780 @offset=1920 fp=0x     (null)

	CPU: 7 PID: 1945 Comm: sh Tainted: G    B   W  OE   4.1.46 #8
	Hardware name: linux,dummy-virt (DT)
	Call trace:
	[<0008d2a0>] dump_backtrace+0x0/0x220
	[<0008d4e0>] show_stack+0x20/0x30
	[<00ff2278>] dump_stack+0xa8/0xcc
	[<002dc6c8>] print_trailer+0xf8/0x160
	[<002e20d8>] object_err+0x48/0x60
	[<002e48dc>] kasan_report+0x26c/0x5a0
	[<002e39a0>] __asan_load8+0x60/0x80
	[<01000054>] trampoline_probe_handler+0xb4/0x2f0
	[<00ffff38>] kretprobe_trampoline+0x54/0xbc
	Memory state around the buggy address:
 	b732a680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 	b732a700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
	>b732a780: 00 00 00 00 07 fc fc fc fc fc fc fc fc fc fc fc
                               ^

If data_size is invalid, then we should not register it.

Signed-off-by: Cheng Jian <cj.chengjian@xxxxxxxxxx>
Reported-by: Kong ZhangHuan <kongzhanghuan@xxxxxxxxxx>
---
 kernel/kprobes.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index da2ccf1..8002f28 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1924,6 +1924,9 @@ int register_kretprobe(struct kretprobe *rp)
 	int i;
 	void *addr;
 
+	if ((ssize_t)rp->data_size < 0)
+		return -EINVAL;
+
 	if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset))
 		return -EINVAL;
 
-- 
1.8.3.1