linux-kernel - Re: [PATCH] debugfs: Fix memleak in debugfs_change

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Message-Id: <DF2B5BG0KOPL.3MV172W4FI1HP@kernel.org>
Date: Fri, 19 Dec 2025 16:44:55 +0100
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Kuniyuki Iwashima" <kuniyu@...gle.com>
Cc: "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, "Christian Brauner" <brauner@...nel.org>, "NeilBrown"
 <neil@...wn.name>, "Kuniyuki Iwashima" <kuni1840@...il.com>,
 <linux-kernel@...r.kernel.org>,
 <syzbot+3d7ca9c802c547f8550a@...kaller.appspotmail.com>
Subject: Re: [PATCH] debugfs: Fix memleak in debugfs_change_name().

On Mon Dec 8, 2025 at 10:45 AM CET, Kuniyuki Iwashima wrote:
> syzbot reported memleak in debugfs_change_name(). [0]
>
> When lookup_noperm_unlocked() fails, new_name is leaked.
>
> Let's fix it by reusing to kfree_const() at the end of
> debugfs_change_name().
>
> [0]:
> BUG: memory leak
> unreferenced object 0xffff8881110bb308 (size 8):
>   comm "syz.0.17", pid 6090, jiffies 4294942958
>   hex dump (first 8 bytes):
>     2e 00 00 00 00 00 00 00                          ........
>   backtrace (crc ecfc7064):
>     kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
>     slab_post_alloc_hook mm/slub.c:4953 [inline]
>     slab_alloc_node mm/slub.c:5258 [inline]
>     __do_kmalloc_node mm/slub.c:5651 [inline]
>     __kmalloc_node_track_caller_noprof+0x3b2/0x670 mm/slub.c:5759
>     __kmemdup_nul mm/util.c:64 [inline]
>     kstrdup+0x3c/0x80 mm/util.c:84
>     kstrdup_const+0x63/0x80 mm/util.c:104
>     kvasprintf_const+0xca/0x110 lib/kasprintf.c:48
>     debugfs_change_name+0xf6/0x5d0 fs/debugfs/inode.c:854
>     cfg80211_dev_rename+0xd8/0x110 net/wireless/core.c:149
>     nl80211_set_wiphy+0x102/0x1770 net/wireless/nl80211.c:3844
>     genl_family_rcv_msg_doit+0x11e/0x190 net/netlink/genetlink.c:1115
>     genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
>     genl_rcv_msg+0x2fd/0x440 net/netlink/genetlink.c:1210
>     netlink_rcv_skb+0x93/0x1d0 net/netlink/af_netlink.c:2550
>     genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
>     netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
>     netlink_unicast+0x3a3/0x4f0 net/netlink/af_netlink.c:1344
>     netlink_sendmsg+0x335/0x6b0 net/netlink/af_netlink.c:1894
>     sock_sendmsg_nosec net/socket.c:718 [inline]
>     __sock_sendmsg net/socket.c:733 [inline]
>     ____sys_sendmsg+0x562/0x5a0 net/socket.c:2608
>     ___sys_sendmsg+0xc8/0x130 net/socket.c:2662
>     __sys_sendmsg+0xc7/0x140 net/socket.c:2694
>
> Fixes: 833d2b3a072f7 ("Add start_renaming_two_dentries()")
> Reported-by: syzbot+3d7ca9c802c547f8550a@...kaller.appspotmail.com
> Closes: https://lore.kernel.org/all/69369d82.a70a0220.38f243.009f.GAE@google.com/
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>

Applied to driver-core-linus, thanks!

    [ Fix minor typo in commit message. - Danilo ]