CVE-2024-50035

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

ppp: fix ppp_async_encode() illegal access

syzbot reported an issue in ppp_async_encode() [1]

In this case, pppoe_sendmsg() is called with a zero size.

Then ppp_async_encode() is called with an empty skb.

BUG: KMSAN: uninit-value in ppp_async_encode drivers/net/ppp/ppp_async.c:545 [inline]

BUG: KMSAN: uninit-value in ppp_async_push+0xb4f/0x2660 drivers/net/ppp/ppp_async.c:675

ppp_async_encode drivers/net/ppp/ppp_async.c:545 [inline]

ppp_async_push+0xb4f/0x2660 drivers/net/ppp/ppp_async.c:675

ppp_async_send+0x130/0x1b0 drivers/net/ppp/ppp_async.c:634

ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2280 [inline]

ppp_input+0x1f1/0xe60 drivers/net/ppp/ppp_generic.c:2304

pppoe_rcv_core+0x1d3/0x720 drivers/net/ppp/pppoe.c:379

sk_backlog_rcv+0x13b/0x420 include/net/sock.h:1113

__release_sock+0x1da/0x330 net/core/sock.c:3072

release_sock+0x6b/0x250 net/core/sock.c:3626

pppoe_sendmsg+0x2b8/0xb90 drivers/net/ppp/pppoe.c:903

sock_sendmsg_nosec net/socket.c:729 [inline]

__sock_sendmsg+0x30f/0x380 net/socket.c:744

____sys_sendmsg+0x903/0xb60 net/socket.c:2602

___sys_sendmsg+0x28d/0x3c0 net/socket.c:2656

__sys_sendmmsg+0x3c1/0x960 net/socket.c:2742

__do_sys_sendmmsg net/socket.c:2771 [inline]

__se_sys_sendmmsg net/socket.c:2768 [inline]

__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2768

x64_sys_call+0xb6e/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:308

do_syscall_x64 arch/x86/entry/common.c:52 [inline]

do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83

entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:

slab_post_alloc_hook mm/slub.c:4092 [inline]

slab_alloc_node mm/slub.c:4135 [inline]

kmem_cache_alloc_node_noprof+0x6bf/0xb80 mm/slub.c:4187

kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:587

__alloc_skb+0x363/0x7b0 net/core/skbuff.c:678

alloc_skb include/linux/skbuff.h:1322 [inline]

sock_wmalloc+0xfe/0x1a0 net/core/sock.c:2732

pppoe_sendmsg+0x3a7/0xb90 drivers/net/ppp/pppoe.c:867

sock_sendmsg_nosec net/socket.c:729 [inline]

__sock_sendmsg+0x30f/0x380 net/socket.c:744

____sys_sendmsg+0x903/0xb60 net/socket.c:2602

___sys_sendmsg+0x28d/0x3c0 net/socket.c:2656

__sys_sendmmsg+0x3c1/0x960 net/socket.c:2742

__do_sys_sendmmsg net/socket.c:2771 [inline]

__se_sys_sendmmsg net/socket.c:2768 [inline]

__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2768

x64_sys_call+0xb6e/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:308

do_syscall_x64 arch/x86/entry/common.c:52 [inline]

do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83

entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 5411 Comm: syz.1.14 Not tainted 6.12.0-rc1-syzkaller-00165-g360c1f1f24c6 #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024