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;