On Tue, Jul 21, 2020 at 08:18:11PM +0800, Yang Yingliang wrote: > > On 2020/7/21 19:54, Yang Yingliang wrote: > > > > On 2020/7/21 18:48, Greg KH wrote: > > > On Tue, Jul 21, 2020 at 02:38:52PM +0000, Yang Yingliang wrote: > > > > 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 <yangyingli...@huawei.com> > > > > --- > > > > drivers/tty/serial/8250/8250_core.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > Does this fix a specific commit, or has this issue always been present? > > > What has caused it to happen now that no one else has seen this? > > > > I think it's always been present on the arch that not defined > > SERIAL_PORT_DFNS. > > > > I got this on arm64 and here is the C reproducer: > > > > // autogenerated by syzkaller (https://github.com/google/syzkaller) > > > > #define _GNU_SOURCE > > > > #include <endian.h> > > #include <stdint.h> > > #include <stdio.h> > > #include <stdlib.h> > > #include <string.h> > > #include <sys/syscall.h> > > #include <sys/types.h> > > #include <unistd.h> > > > > #ifndef __NR_ioctl > > #define __NR_ioctl 29 > > #endif > > #ifndef __NR_mmap > > #define __NR_mmap 222 > > #endif > > #ifndef __NR_openat > > #define __NR_openat 56 > > #endif > > > > uint64_t r[1] = {0xffffffffffffffff}; > > > > int main(void) > > { > > syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 3ul, 0x32ul, -1, 0); > > intptr_t res = 0; > > memcpy((void*)0x20000040, "/dev/ttyS3\000", 11); > > res = syscall(__NR_openat, 0xffffffffffffff9cul, 0x20000040ul, > > 0x401ul, 0ul); > > if (res != -1) > > r[0] = res; > > syscall(__NR_ioctl, r[0], 0x5412ul, 0x20000080ul); > > return 0; > > } > > > It's can be reproduced with CONFIG_SERIAL_8250_RUNTIME_UARTS=8 and > > by opening ttyS4 on x86_64. Because the size of SERIAL_PORT_DFNS is 4 and > > the pointers of ttyS4 ~ ttyS7 won't be initialized.
Ah, good catch, yeah, that's not nice. I'll go queue this up now, thanks for the fix! greg k-h
