[PATCH 4.4 32/54] serial: 8250: fix null-ptr-deref in serial8250_start_tx()

Greg Kroah-Hartman
2020-07-30T08:15:18Z

From: Yang Yingliang <yangyingliang@huawei.com>

commit f4c23a140d80ef5e6d3d1f8f57007649014b60fa upstream.

I got null-ptr-deref in serial8250_start_tx():

[ 78.114630] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[ 78.123778] Mem abort info:
[ 78.126560] ESR = 0x86000007
[ 78.129603] EC = 0x21: IABT (current EL), IL = 32 bits
[ 78.134891] SET = 0, FnV = 0
[ 78.137933] EA = 0, S1PTW = 0
[ 78.141064] user pgtable: 64k pages, 48-bit VAs, pgdp=00000027d41a8600
[ 78.147562] [0000000000000000] pgd=00000027893f0003, p4d=00000027893f0003, pud=00000027893f0003, pmd=00000027c9a20003, pte=0000000000000000
[ 78.160029] Internal error: Oops: 86000007 [#1] SMP
[ 78.164886] Modules linked in: sunrpc vfat fat aes_ce_blk crypto_simd cryptd aes_ce_cipher crct10dif_ce ghash_ce sha2_ce sha256_arm64 sha1_ce ses enclosure sg sbsa_gwdt ipmi_ssif spi_dw_mmio sch_fq_codel vhost_net tun vhost vhost_iotlb tap ip_tables ext4 mbcache jbd2 ahci hisi_sas_v3_hw libahci hisi_sas_main libsas hns3 scsi_transport_sas hclge libata megaraid_sas ipmi_si hnae3 ipmi_devintf ipmi_msghandler br_netfilter bridge stp llc nvme nvme_core xt_sctp sctp libcrc32c dm_mod nbd
[ 78.207383] CPU: 11 PID: 23258 Comm: null-ptr Not tainted 5.8.0-rc6+ #48
[ 78.214056] Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V3.B210.01 03/12/2020
[ 78.222888] pstate: 80400089 (Nzcv daIf +PAN -UAO BTYPE=--)
[ 78.228435] pc : 0x0
[ 78.230618] lr : serial8250_start_tx+0x160/0x260
[ 78.235215] sp : ffff800062eefb80
[ 78.238517] x29: ffff800062eefb80 x28: 0000000000000fff
[ 78.243807] x27: ffff800062eefd80 x26: ffff202fd83b3000
[ 78.249098] x25: ffff800062eefd80 x24: ffff202fd83b3000
[ 78.254388] x23: ffff002fc5e50be8 x22: 0000000000000002
[ 78.259679] x21: 0000000000000001 x20: 0000000000000000
[ 78.264969] x19: ffffa688827eecc8 x18: 0000000000000000
[ 78.270259] x17: 0000000000000000 x16: 0000000000000000
[ 78.275550] x15: ffffa68881bc67a8 x14: 00000000000002e6
[ 78.280841] x13: ffffa68881bc67a8 x12: 000000000000c539
[ 78.286131] x11: d37a6f4de9bd37a7 x10: ffffa68881cccff0
[ 78.291421] x9 : ffffa68881bc6000 x8 : ffffa688819daa88
[ 78.296711] x7 : ffffa688822a0f20 x6 : ffffa688819e0000
[ 78.302002] x5 : ffff800062eef9d0 x4 : ffffa68881e707a8
[ 78.307292] x3 : 0000000000000000 x2 : 0000000000000002
[ 78.312582] x1 : 0000000000000001 x0 : ffffa688827eecc8
[ 78.317873] Call trace:
[ 78.320312] 0x0
[ 78.322147] __uart_start.isra.9+0x64/0x78
[ 78.326229] uart_start+0xb8/0x1c8
[ 78.329620] uart_flush_chars+0x24/0x30
[ 78.333442] n_tty_receive_buf_common+0x7b0/0xc30
[ 78.338128] n_tty_receive_buf+0x44/0x2c8
[ 78.342122] tty_ioctl+0x348/0x11f8
[ 78.345599] ksys_ioctl+0xd8/0xf8
[ 78.348903] __arm64_sys_ioctl+0x2c/0xc8
[ 78.352812] el0_svc_common.constprop.2+0x88/0x1b0
[ 78.357583] do_el0_svc+0x44/0xd0
[ 78.360887] el0_sync_handler+0x14c/0x1d0
[ 78.364880] el0_sync+0x140/0x180
[ 78.368185] Code: bad PC value

SERIAL_PORT_DFNS is not defined on each arch, if it's not defined,
serial8250_set_defaults() won't be called in serial8250_isa_init_ports(),
so the p->serial_in pointer won't be initialized, and it leads a null-ptr-deref.
Fix this problem by calling serial8250_set_defaults() after init uart port.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200721143852.4058352-1-yangyingliang@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/tty/serial/8250/8250_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -530,6 +530,7 @@ static void __init serial8250_isa_init_p
*/
up->mcr_mask = ~ALPHA_KLUDGE_MCR;
up->mcr_force = ALPHA_KLUDGE_MCR;
+ serial8250_set_defaults(up);
}

/* chain base port ops to support Remote Supervisor Adapter */
@@ -553,7 +554,6 @@ static void __init serial8250_isa_init_p
port->membase = old_serial_port[i].iomem_base;
port->iotype = old_serial_port[i].io_type;
port->regshift = old_serial_port[i].iomem_reg_shift;
- serial8250_set_defaults(up);

port->irqflags |= irqflag;
if (serial8250_isa_config != NULL)