[PATCH 5.9 597/757] firmware: arm_scmi: Fix NULL pointer dereference in mailbox_chan_free

Greg Kroah-Hartman
2020-10-27T16:02:36Z

From: Sudeep Holla <sudeep.holla@arm.com>

[ Upstream commit 6ed6c558234f0b6c22e47a3c2feddce3d02324dd ]

scmi_mailbox is obtained from cinfo->transport_info and the first
call to mailbox_chan_free frees the channel and sets cinfo->transport_info
to NULL. Care is taken to check for non NULL smbox->chan but smbox can
itself be NULL. Fix it by checking for it without which, kernel crashes
with below NULL pointer dereference and eventually kernel panic.

Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000038
Modules linked in: scmi_module(-)
Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno
Development Platform, BIOS EDK II Sep 2 2020
pstate: 80000005 (Nzcv daif -PAN -UAO BTYPE=--)
pc : mailbox_chan_free+0x2c/0x70 [scmi_module]
lr : idr_for_each+0x6c/0xf8
Call trace:
mailbox_chan_free+0x2c/0x70 [scmi_module]
idr_for_each+0x6c/0xf8
scmi_remove+0xa8/0xf0 [scmi_module]
platform_drv_remove+0x34/0x58
device_release_driver_internal+0x118/0x1f0
driver_detach+0x58/0xe8
bus_remove_driver+0x64/0xe0
driver_unregister+0x38/0x68
platform_driver_unregister+0x1c/0x28
scmi_driver_exit+0x38/0x44 [scmi_module]
---[ end trace 17bde19f50436de9 ]---
Kernel panic - not syncing: Fatal exception
SMP: stopping secondary CPUs
Kernel Offset: 0x1d0000 from 0xffff800010000000
PHYS_OFFSET: 0x80000000
CPU features: 0x0240022,25806004
Memory Limit: none
---[ end Kernel panic - not syncing: Fatal exception ]---

Link: https://lore.kernel.org/r/20200908112611.31515-1-sudeep.holla@arm.com
Fixes: 5c8a47a5a91d ("firmware: arm_scmi: Make scmi core independent of the transport type")
Cc: Cristian Marussi <cristian.marussi@arm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/firmware/arm_scmi/mailbox.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/mailbox.c b/drivers/firmware/arm_scmi/mailbox.c
index 6998dc86b5ce8..b797a713c3313 100644
--- a/drivers/firmware/arm_scmi/mailbox.c
+++ b/drivers/firmware/arm_scmi/mailbox.c
@@ -110,7 +110,7 @@ static int mailbox_chan_free(int id, void *p, void *data)
struct scmi_chan_info *cinfo = p;
struct scmi_mailbox *smbox = cinfo->transport_info;

- if (!IS_ERR(smbox->chan)) {
+ if (smbox && !IS_ERR(smbox->chan)) {
mbox_free_channel(smbox->chan);
cinfo->transport_info = NULL;
smbox->chan = NULL;
--
2.25.1