[PATCH AUTOSEL 6.0 07/18] chardev: Fix potential memory leak when cdev_add() failed

Sasha Levin
2022-12-24T01:34:03Z

From: Shang XiaoJing <shangxiaojing@huawei.com>

[ Upstream commit 4634c973096a64662a24d9914c47cebc2a8b72f4 ]

Some init function of cdev(like comedi) will call kobject_set_name()
before cdev_add(), but won't free the cdev.kobj.name or put the ref cnt
of cdev.kobj when cdev_add() failed. As the result, cdev.kobj.name will
be leaked.

Free the name of kobject in cdev_add() fail path to prevent memleak. With
this fix, the callers don't need to care about freeing the name of
kobject if cdev_add() fails.

unreferenced object 0xffff8881000fa8c0 (size 8):
comm "modprobe", pid 239, jiffies 4294905173 (age 51.308s)
hex dump (first 8 bytes):
63 6f 6d 65 64 69 00 ff comedi..
backtrace:
[<000000005f9878f7>] __kmalloc_node_track_caller+0x4c/0x1c0
[<000000000fd70302>] kstrdup+0x3f/0x70
[<000000009428bc33>] kstrdup_const+0x46/0x60
[<00000000ed50d9de>] kvasprintf_const+0xdb/0xf0
[<00000000b2766964>] kobject_set_name_vargs+0x3c/0xe0
[<00000000f2424ef7>] kobject_set_name+0x62/0x90
[<000000005d5a125b>] 0xffffffffa0013098
[<00000000f331e663>] do_one_initcall+0x7a/0x380
[<00000000aa7bac96>] do_init_module+0x5c/0x230
[<000000005fd72335>] load_module+0x227d/0x2420
[<00000000ad550cf1>] __do_sys_finit_module+0xd5/0x140
[<00000000069a60c5>] do_syscall_64+0x3f/0x90
[<00000000c5e0d521>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Suggested-by: Greg KH <gregkh@linuxfoundation.org>
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
Link: https://lore.kernel.org/r/20221102072659.23671-1-shangxiaojing@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/char_dev.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/char_dev.c b/fs/char_dev.c
index ba0ded7842a7..340e4543b24a 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -483,17 +483,24 @@ int cdev_add(struct cdev *p, dev_t dev, unsigned count)
p->dev = dev;
p->count = count;

- if (WARN_ON(dev == WHITEOUT_DEV))
- return -EBUSY;
+ if (WARN_ON(dev == WHITEOUT_DEV)) {
+ error = -EBUSY;
+ goto err;
+ }

error = kobj_map(cdev_map, dev, count, NULL,
exact_match, exact_lock, p);
if (error)
- return error;
+ goto err;

kobject_get(p->kobj.parent);

return 0;
+
+err:
+ kfree_const(p->kobj.name);
+ p->kobj.name = NULL;
+ return error;
}

/**
--
2.35.1