[PATCH AUTOSEL 6.0 11/18] char: xillybus: Fix trivial bug with mutex

Sasha Levin
2022-12-24T01:33:45Z

From: Eli Billauer <eli.billauer@gmail.com>

[ Upstream commit c002f04c0bc79ec00d4beb75fb631d5bf37419bd ]

@unit_mutex protects @unit from being freed, so obviously it should be
released after @unit is used, and not before.

This is a follow-up to commit 282a4b71816b ("char: xillybus: Prevent
use-after-free due to race condition") which ensures, among others, the
protection of @private_data after @unit_mutex has been released.

Reported-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Eli Billauer <eli.billauer@gmail.com>
Link: https://lore.kernel.org/r/20221117071825.3942-1-eli.billauer@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/char/xillybus/xillybus_class.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/char/xillybus/xillybus_class.c b/drivers/char/xillybus/xillybus_class.c
index 0f238648dcfe..e9a288e61c15 100644
--- a/drivers/char/xillybus/xillybus_class.c
+++ b/drivers/char/xillybus/xillybus_class.c
@@ -227,14 +227,15 @@ int xillybus_find_inode(struct inode *inode,
break;
}

- mutex_unlock(&unit_mutex);
-
- if (!unit)
+ if (!unit) {
+ mutex_unlock(&unit_mutex);
return -ENODEV;
+ }

*private_data = unit->private_data;
*index = minor - unit->lowest_minor;

+ mutex_unlock(&unit_mutex);
return 0;
}
EXPORT_SYMBOL(xillybus_find_inode);
--
2.35.1