linux-kernel - [PATCH] xfs: Fix unreferenced object reported by kmemleak in xfs_sysfs

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Date:   Mon, 17 Oct 2022 11:00:29 +0800
From:   Li Zetao <lizetao1@...wei.com>
To:     <djwong@...nel.org>, <dchinner@...hat.com>, <bfoster@...hat.com>
CC:     <lizetao1@...wei.com>, <linux-xfs@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] xfs: Fix unreferenced object reported by kmemleak in xfs_sysfs_init()

kmemleak reported a sequence of memory leaks, and one of them indicated we
failed to free a pointer:
  comm "mount", pid 19610, jiffies 4297086464 (age 60.635s)
    hex dump (first 8 bytes):
      73 64 61 00 81 88 ff ff                          sda.....
    backtrace:
      [<00000000d77f3e04>] kstrdup_const+0x46/0x70
      [<00000000e51fa804>] kobject_set_name_vargs+0x2f/0xb0
      [<00000000247cd595>] kobject_init_and_add+0xb0/0x120
      [<00000000f9139aaf>] xfs_mountfs+0x367/0xfc0
      [<00000000250d3caf>] xfs_fs_fill_super+0xa16/0xdc0
      [<000000008d873d38>] get_tree_bdev+0x256/0x390
      [<000000004881f3fa>] vfs_get_tree+0x41/0xf0
      [<000000008291ab52>] path_mount+0x9b3/0xdd0
      [<0000000022ba8f2d>] __x64_sys_mount+0x190/0x1d0

As mentioned in kobject_init_and_add() comment, if this function
returns an error, kobject_put() must be called to properly clean up
the memory associated with the object. Apparently, xfs_sysfs_init()
does not follow such a requirement. When kobject_init_and_add()
returns an error, the space of kobj->kobject.name alloced by
kstrdup_const() is unfree, which will cause the above stack.

Fix it by adding kobject_put() when kobject_init_and_add returns an
error.

Fixes: a31b1d3d89e4 ("xfs: add xfs_mount sysfs kobject")
Signed-off-by: Li Zetao <lizetao1@...wei.com>
---
 fs/xfs/xfs_sysfs.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_sysfs.h b/fs/xfs/xfs_sysfs.h
index 43585850f154..513095e353a5 100644
--- a/fs/xfs/xfs_sysfs.h
+++ b/fs/xfs/xfs_sysfs.h
@@ -33,10 +33,15 @@ xfs_sysfs_init(
 	const char		*name)
 {
 	struct kobject		*parent;
+	int err;
 
 	parent = parent_kobj ? &parent_kobj->kobject : NULL;
 	init_completion(&kobj->complete);
-	return kobject_init_and_add(&kobj->kobject, ktype, parent, "%s", name);
+	err = kobject_init_and_add(&kobj->kobject, ktype, parent, "%s", name);
+	if (err)
+		kobject_put(&kobj->kobject);
+
+	return err;
 }
 
 static inline void
-- 
2.31.1