[PATCH 6.12 046/567] netrom: Fix memory leak in nr_sendmsg()

Greg Kroah-Hartman
2026-01-06T17:16:45Z

From: Wang Liang <wangliang74@huawei.com>

[ Upstream commit 613d12dd794e078be8ff3cf6b62a6b9acf7f4619 ]

syzbot reported a memory leak [1].

When function sock_alloc_send_skb() return NULL in nr_output(), the
original skb is not freed, which was allocated in nr_sendmsg(). Fix this
by freeing it before return.

[1]
BUG: memory leak
unreferenced object 0xffff888129f35500 (size 240):
comm "syz.0.17", pid 6119, jiffies 4294944652
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 10 52 28 81 88 ff ff ..........R(....
backtrace (crc 1456a3e4):
kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
slab_post_alloc_hook mm/slub.c:4983 [inline]
slab_alloc_node mm/slub.c:5288 [inline]
kmem_cache_alloc_node_noprof+0x36f/0x5e0 mm/slub.c:5340
__alloc_skb+0x203/0x240 net/core/skbuff.c:660
alloc_skb include/linux/skbuff.h:1383 [inline]
alloc_skb_with_frags+0x69/0x3f0 net/core/skbuff.c:6671
sock_alloc_send_pskb+0x379/0x3e0 net/core/sock.c:2965
sock_alloc_send_skb include/net/sock.h:1859 [inline]
nr_sendmsg+0x287/0x450 net/netrom/af_netrom.c:1105
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
sock_write_iter+0x293/0x2a0 net/socket.c:1195
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x45d/0x710 fs/read_write.c:686
ksys_write+0x143/0x170 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d7abc36bbbb6d7d40b58
Tested-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Wang Liang <wangliang74@huawei.com>
Link: https://patch.msgid.link/20251129041315.1550766-1-wangliang74@huawei.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netrom/nr_out.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netrom/nr_out.c b/net/netrom/nr_out.c
index 5e531394a724b..2b3cbceb0b52d 100644
--- a/net/netrom/nr_out.c
+++ b/net/netrom/nr_out.c
@@ -43,8 +43,10 @@ void nr_output(struct sock *sk, struct sk_buff *skb)
frontlen = skb_headroom(skb);

while (skb->len > 0) {
- if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
+ if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL) {
+ kfree_skb(skb);
return;
+ }

skb_reserve(skbn, frontlen);

--
2.51.0