5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit 40dddd4b8bd08a69471efd96107a4e1c73fabefc ]
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
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+1d121645899e7692f92a@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
Link: https://patch.msgid.link/20241009185802.3763282-1-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/net/ppp/ppp_async.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ppp/ppp_async.c b/drivers/net/ppp/ppp_async.c
index 34c31d6da734c..c41eeecb5a106 100644
--- a/drivers/net/ppp/ppp_async.c
+++ b/drivers/net/ppp/ppp_async.c
@@ -551,7 +551,7 @@ ppp_async_encode(struct asyncppp *ap)
* and 7 (code-reject) must be sent as though no options
* had been negotiated.
*/
- islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
+ islcp = proto == PPP_LCP && count >= 3 && 1 <= data[2] && data[2] <= 7;
if (i == 0) {
if (islcp)
--
2.43.0
