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Subject[PATCH] kprobe : fix out-of-bounds in register_kretprobe when parsing negative data_size
Date
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@huawei.com>
Reported-by: Kong ZhangHuan <kongzhanghuan@huawei.com>
---
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
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