[PATCH AUTOSEL 5.4 09/18] scsi: mpt3sas: Fix unlock imbalance

[Sasha Levin <sashal@kernel.org>]

From: Damien Le Moal <damien.lemoal@wdc.com>

[ Upstream commit cb551b8dc079d2ef189145782627c99cb68c0255 ]

In BRM_status_show(), if the condition "!ioc->is_warpdrive" tested on entry
to the function is true, a "goto out" is called. This results in unlocking
ioc->pci_access_mutex without this mutex lock being taken.  This generates
the following splat:

[ 1148.539883] mpt3sas_cm2: BRM_status_show: BRM attribute is only for warpdrive
[ 1148.547184]
[ 1148.548708] =====================================
[ 1148.553501] WARNING: bad unlock balance detected!
[ 1148.558277] 5.8.0-rc3+ #827 Not tainted
[ 1148.562183] -------------------------------------
[ 1148.566959] cat/5008 is trying to release lock (&ioc->pci_access_mutex) at:
[ 1148.574035] [<ffffffffc070b7a3>] BRM_status_show+0xd3/0x100 [mpt3sas]
[ 1148.580574] but there are no more locks to release!
[ 1148.585524]
[ 1148.585524] other info that might help us debug this:
[ 1148.599624] 3 locks held by cat/5008:
[ 1148.607085]  #0: ffff92aea3e392c0 (&p->lock){+.+.}-{3:3}, at: seq_read+0x34/0x480
[ 1148.618509]  #1: ffff922ef14c4888 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x2a/0xb0
[ 1148.630729]  #2: ffff92aedb5d7310 (kn->active#224){.+.+}-{0:0}, at: kernfs_seq_start+0x32/0xb0
[ 1148.643347]
[ 1148.643347] stack backtrace:
[ 1148.655259] CPU: 73 PID: 5008 Comm: cat Not tainted 5.8.0-rc3+ #827
[ 1148.665309] Hardware name: HGST H4060-S/S2600STB, BIOS SE5C620.86B.02.01.0008.031920191559 03/19/2019
[ 1148.678394] Call Trace:
[ 1148.684750]  dump_stack+0x78/0xa0
[ 1148.691802]  lock_release.cold+0x45/0x4a
[ 1148.699451]  __mutex_unlock_slowpath+0x35/0x270
[ 1148.707675]  BRM_status_show+0xd3/0x100 [mpt3sas]
[ 1148.716092]  dev_attr_show+0x19/0x40
[ 1148.723664]  sysfs_kf_seq_show+0x87/0x100
[ 1148.731193]  seq_read+0xbc/0x480
[ 1148.737882]  vfs_read+0xa0/0x160
[ 1148.744514]  ksys_read+0x58/0xd0
[ 1148.751129]  do_syscall_64+0x4c/0xa0
[ 1148.757941]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 1148.766240] RIP: 0033:0x7f1230566542
[ 1148.772957] Code: Bad RIP value.
[ 1148.779206] RSP: 002b:00007ffeac1bcac8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[ 1148.790063] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f1230566542
[ 1148.800284] RDX: 0000000000020000 RSI: 00007f1223460000 RDI: 0000000000000003
[ 1148.810474] RBP: 00007f1223460000 R08: 00007f122345f010 R09: 0000000000000000
[ 1148.820641] R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000000000
[ 1148.830728] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000

Fix this by returning immediately instead of jumping to the out label.

Link: https://lore.kernel.org/r/20200701085254.51740-1-damien.lemoal@wdc.com
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Acked-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/scsi/mpt3sas/mpt3sas_ctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_ctl.c b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
index b95f7d062ea44..82c4ecc16f191 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_ctl.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
@@ -2921,7 +2921,7 @@ BRM_status_show(struct device *cdev, struct device_attribute *attr,
 	if (!ioc->is_warpdrive) {
 		ioc_err(ioc, "%s: BRM attribute is only for warpdrive\n",
 			__func__);
-		goto out;
+		return 0;
 	}
 	/* pci_access_mutex lock acquired by sysfs show path */
 	mutex_lock(&ioc->pci_access_mutex);
-- 
2.25.1