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Subject[PATCH AUTOSEL 4.4 2/6] spi: bitbang: Fix NULL pointer dereference in spi_unregister_master
Date
From: YueHaibing <yuehaibing@huawei.com>

[ Upstream commit 5caaf29af5ca82d5da8bc1d0ad07d9e664ccf1d8 ]

If spi_register_master fails in spi_bitbang_start
because device_add failure, We should return the
error code other than 0, otherwise calling
spi_bitbang_stop may trigger NULL pointer dereference
like this:

BUG: KASAN: null-ptr-deref in __list_del_entry_valid+0x45/0xd0
Read of size 8 at addr 0000000000000000 by task syz-executor.0/3661

CPU: 0 PID: 3661 Comm: syz-executor.0 Not tainted 5.1.0+ #28
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
Call Trace:
dump_stack+0xa9/0x10e
? __list_del_entry_valid+0x45/0xd0
? __list_del_entry_valid+0x45/0xd0
__kasan_report+0x171/0x18d
? __list_del_entry_valid+0x45/0xd0
kasan_report+0xe/0x20
__list_del_entry_valid+0x45/0xd0
spi_unregister_controller+0x99/0x1b0
spi_lm70llp_attach+0x3ae/0x4b0 [spi_lm70llp]
? 0xffffffffc1128000
? klist_next+0x131/0x1e0
? driver_detach+0x40/0x40 [parport]
port_check+0x3b/0x50 [parport]
bus_for_each_dev+0x115/0x180
? subsys_dev_iter_exit+0x20/0x20
__parport_register_driver+0x1f0/0x210 [parport]
? 0xffffffffc1150000
do_one_initcall+0xb9/0x3b5
? perf_trace_initcall_level+0x270/0x270
? kasan_unpoison_shadow+0x30/0x40
? kasan_unpoison_shadow+0x30/0x40
do_init_module+0xe0/0x330
load_module+0x38eb/0x4270
? module_frob_arch_sections+0x20/0x20
? kernel_read_file+0x188/0x3f0
? find_held_lock+0x6d/0xd0
? fput_many+0x1a/0xe0
? __do_sys_finit_module+0x162/0x190
__do_sys_finit_module+0x162/0x190
? __ia32_sys_init_module+0x40/0x40
? __mutex_unlock_slowpath+0xb4/0x3f0
? wait_for_completion+0x240/0x240
? vfs_write+0x160/0x2a0
? lockdep_hardirqs_off+0xb5/0x100
? mark_held_locks+0x1a/0x90
? do_syscall_64+0x14/0x2a0
do_syscall_64+0x72/0x2a0
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 702a4879ec33 ("spi: bitbang: Let spi_bitbang_start() take a reference to master")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi-bitbang.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-bitbang.c b/drivers/spi/spi-bitbang.c
index 3aa9e6e3dac8..4ef54436b9d4 100644
--- a/drivers/spi/spi-bitbang.c
+++ b/drivers/spi/spi-bitbang.c
@@ -392,7 +392,7 @@ int spi_bitbang_start(struct spi_bitbang *bitbang)
if (ret)
spi_master_put(master);

- return 0;
+ return ret;
}
EXPORT_SYMBOL_GPL(spi_bitbang_start);

--
2.20.1
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