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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, Denis Kirjanov <kda@linux-powerpc.org>,
        "YueHaibing" <yuehaibing@huawei.com>,
        "Mark Brown" <broonie@kernel.org>,
        "Mukesh Ojha" <mojha@codeaurora.org>,
        "Axel Lin" <axel.lin@ingics.com>,
        "Geert Uytterhoeven" <geert+renesas@glider.be>,
        "Hulk Robot" <hulkci@huawei.com>
Date:   Wed, 02 Oct 2019 20:06:51 +0100
Message-ID: <lsq.1570043211.344502621@decadent.org.uk>
Subject: [PATCH 3.16 02/87] spi: bitbang: Fix NULL pointer dereference in
 spi_unregister_master
In-Reply-To: <lsq.1570043210.379046399@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: YueHaibing <yuehaibing@huawei.com>

commit 5caaf29af5ca82d5da8bc1d0ad07d9e664ccf1d8 upstream.

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: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/spi/spi-bitbang.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/spi/spi-bitbang.c
+++ b/drivers/spi/spi-bitbang.c
@@ -462,7 +462,7 @@ int spi_bitbang_start(struct spi_bitbang
 	if (ret)
 		spi_master_put(master);
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(spi_bitbang_start);