linux-kernel - [PATCH] scsi: ufs: Fix NULL pointer dereference in ufshcd_config_vreg

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Date:   Wed, 14 Aug 2019 15:59:50 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     "Martin K . Petersen" <martin.petersen@...cle.com>,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>
Subject: [PATCH] scsi: ufs: Fix NULL pointer dereference in ufshcd_config_vreg_hpm()

Fix the following BUG:

  [ 187.065689] BUG: kernel NULL pointer dereference, address: 000000000000001c
  [ 187.065790] RIP: 0010:ufshcd_vreg_set_hpm+0x3c/0x110 [ufshcd_core]
  [ 187.065938] Call Trace:
  [ 187.065959] ufshcd_resume+0x72/0x290 [ufshcd_core]
  [ 187.065980] ufshcd_system_resume+0x54/0x140 [ufshcd_core]
  [ 187.065993] ? pci_pm_restore+0xb0/0xb0
  [ 187.066005] ufshcd_pci_resume+0x15/0x20 [ufshcd_pci]
  [ 187.066017] pci_pm_thaw+0x4c/0x90
  [ 187.066030] dpm_run_callback+0x5b/0x150
  [ 187.066043] device_resume+0x11b/0x220

Voltage regulators are optional, so functions must check they exist
before dereferencing.

Note this issue is hidden if CONFIG_REGULATORS is not set, because the
offending code is optimised away.

Notes for stable:

The issue first appears in commit 57d104c153d3 ("ufs: add UFS power
management support") but is inadvertently fixed in commit 60f0187031c0
("scsi: ufs: disable vccq if it's not needed by UFS device") which in
turn was reverted by commit 730679817d83 ("Revert "scsi: ufs: disable vccq
if it's not needed by UFS device""). So fix applies v3.18 to v4.5 and
v5.1+

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Fixes: 57d104c153d3 ("ufs: add UFS power management support")
Fixes: 730679817d83 ("Revert "scsi: ufs: disable vccq if it's not needed by UFS device"")
Cc: stable@...r.kernel.org
---
 drivers/scsi/ufs/ufshcd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 507fd51e8039..219c435d69a7 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -7105,6 +7105,9 @@ static inline int ufshcd_config_vreg_lpm(struct ufs_hba *hba,
 static inline int ufshcd_config_vreg_hpm(struct ufs_hba *hba,
 					 struct ufs_vreg *vreg)
 {
+	if (!vreg)
+		return 0;
+
 	return ufshcd_config_vreg_load(hba->dev, vreg, vreg->max_uA);
 }
 
-- 
2.17.1