con->partner_altmode[i] ends up with the value 0x2 in the call to typec_altmode_update_active because the array has been accessed out of bounds causing a random memory read. This patch fixes the first occurrence and 2/2 the second. [ 565.452023] BUG: kernel NULL pointer dereference, address: 00000000000002fe [ 565.452025] #PF: supervisor read access in kernel mode [ 565.452026] #PF: error_code(0x0000) - not-present page [ 565.452026] PGD 0 P4D 0 [ 565.452028] Oops: 0000 [#1] PREEMPT SMP NOPTI [ 565.452030] CPU: 0 PID: 502 Comm: kworker/0:3 Not tainted 5.8.0-rc3+ #1 [ 565.452031] Hardware name: LENOVO 20RD002VUS/20RD002VUS, BIOS R16ET25W (1.11 ) 04/21/2020 [ 565.452034] Workqueue: events ucsi_handle_connector_change [typec_ucsi] [ 565.452039] RIP: 0010:typec_altmode_update_active+0x1f/0x100 [typec] [ 565.452040] Code: 0f 1f 84 00 00 00 00 00 0f 1f 00 0f 1f 44 00 00 55 48 89 e5 41 54 53 48 83 ec 10 65 48 8b 04 25 28 00 00 00 48 89 45 e8 31 c0 <0f> b6 87 fc 02 00 00 83 e0 01 40 38 f0 0f 84 95 00 00 00 48 8b 47 [ 565.452041] RSP: 0018:ffffb729c066bdb0 EFLAGS: 00010246 [ 565.452042] RAX: 0000000000000000 RBX: ffffa067c3e64a70 RCX: 0000000000000000 [ 565.452043] RDX: ffffb729c066bd20 RSI: 0000000000000000 RDI: 0000000000000002 [ 565.452044] RBP: ffffb729c066bdd0 R08: 00000083a7910a4f R09: 0000000000000000 [ 565.452044] R10: ffffffffa106a220 R11: 0000000000000000 R12: 0000000000000000 [ 565.452045] R13: ffffa067c3e64a98 R14: ffffa067c3e64810 R15: ffffa067c3e64800 [ 565.452046] FS: 0000000000000000(0000) GS:ffffa067d1400000(0000) knlGS:0000000000000000 [ 565.452047] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 565.452048] CR2: 00000000000002fe CR3: 00000001b060a003 CR4: 00000000003606f0 [ 565.452048] Call Trace: [ 565.452052] ucsi_altmode_update_active+0x83/0xd0 [typec_ucsi] [ 565.452054] ucsi_handle_connector_change+0x1dc/0x320 [typec_ucsi] [ 565.452057] process_one_work+0x1df/0x3d0 [ 565.452059] worker_thread+0x4d/0x3d0 [ 565.452060] ? process_one_work+0x3d0/0x3d0 [ 565.452062] kthread+0x127/0x170 [ 565.452063] ? kthread_park+0x90/0x90 [ 565.452065] ret_from_fork+0x1f/0x30 The failing instruction is; 0x0000000000000380 <+0>: callq 0x385 <typec_altmode_update_active+5> 0x0000000000000385 <+5>: push %rbp 0x0000000000000386 <+6>: mov %rsp,%rbp 0x0000000000000389 <+9>: push %r12 0x000000000000038b <+11>: push %rbx 0x000000000000038c <+12>: sub $0x10,%rsp 0x0000000000000390 <+16>: mov %gs:0x28,%rax 0x0000000000000399 <+25>: mov %rax,-0x18(%rbp) 0x000000000000039d <+29>: xor %eax,%eax 0x000000000000039f <+31>: movzbl 0x2fc(%rdi),%eax <====== 0x00000000000003a6 <+38>: and $0x1,%eax (gdb) list *typec_altmode_update_active+0x1f 0x39f is in typec_altmode_update_active (drivers/usb/typec/class.c:221). 216 */ 217 void typec_altmode_update_active(struct typec_altmode *adev, bool active) 218 { 219 char dir[6]; 220 221 if (adev->active == active) 222 return; 223 224 if (!is_typec_port(adev->dev.parent) && adev->dev.driver) { 225 if (!active) (gdb) list *ucsi_altmode_update_active+0x83 0x12a3 is in ucsi_altmode_update_active (drivers/usb/typec/ucsi/ucsi.c:221). 216 } 217 218 if (cur < UCSI_MAX_ALTMODES) 219 altmode = typec_altmode_get_partner(con->port_altmode[cur]); 220 221 for (i = 0; con->partner_altmode[i]; i++) 222 typec_altmode_update_active(con->partner_altmode[i], 223 con->partner_altmode[i] == altmode); 224 } Fixes: ad74b8649beaf ("usb: typec: ucsi: Preliminary support for alternate modes") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Zwane Mwaikambo <zwane@xxxxxxxxx> --- v2 addresses both instances of array overrun v3 addresses patch submission/formatting issues v4 addresses patch submission/formatting issues v5 adds and cc to stable diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c index affd024190c9..16906519c173 100644 --- a/drivers/usb/typec/ucsi/ucsi.c +++ b/drivers/usb/typec/ucsi/ucsi.c @@ -218,9 +218,10 @@ void ucsi_altmode_update_active(struct ucsi_connector *con) if (cur < UCSI_MAX_ALTMODES) altmode = typec_altmode_get_partner(con->port_altmode[cur]); - for (i = 0; con->partner_altmode[i]; i++) - typec_altmode_update_active(con->partner_altmode[i], - con->partner_altmode[i] == altmode); + for (i = 0; i < UCSI_MAX_ALTMODES; i++) + if (con->partner_altmode[i]) + typec_altmode_update_active(con->partner_altmode[i], + con->partner_altmode[i] == altmode); } static u8 ucsi_altmode_next_mode(struct typec_altmode **alt, u16 svid)