netrom: Fix memory leak in nr_sendmsg()

Overview

In the Linux kernel, the following vulnerability has been resolved:

netrom: Fix memory leak in nr_sendmsg()

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

Affected

• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < f77e538ac4e3adb1882d5bccb7bfdc111b5963d3
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 09efbf54eeaecebe882af603c9939a4b1bb9567e
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 73839497bbde5cd4fd02bbd9c8bc2640780ae65d
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 156a0f6341dce634a825db49ca20b48b1ae9bcc1
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 8d1ccba4b171cd504ecfa47349cb9864fc9d687c
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 51f5fbc1681bdcffcc7d18bf3dfdb2b1278d3977
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 613d12dd794e078be8ff3cf6b62a6b9acf7f4619
• Linux 2.6.12

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.