[PATCH] net: core: fix KMSAN: unint value in tipc_rcv

[HariKrishna Sagala]

#syz test

diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index 76284fc538eb..144b02534196 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -69,6 +69,7 @@ struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)
{
struct sk_buff *skb;

+ gfp |= __GFP_ZERO;
skb = alloc_skb_fclone(BUF_OVERHEAD + size, gfp);
if (skb) {
skb_reserve(skb, BUF_HEADROOM);

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: uninit-value in tipc_rcv

=====================================================
BUG: KMSAN: uninit-value in tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
tipc_l2_rcv_msg+0x213/0x320 net/tipc/bearer.c:668
__netif_receive_skb_list_ptype net/core/dev.c:6127 [inline]
__netif_receive_skb_list_core+0x133e/0x16b0 net/core/dev.c:6169
__netif_receive_skb_list net/core/dev.c:6221 [inline]
netif_receive_skb_list_internal+0xee7/0x1530 net/core/dev.c:6312
gro_normal_list include/net/gro.h:524 [inline]
gro_flush_normal include/net/gro.h:532 [inline]
napi_complete_done+0x3fb/0x7d0 net/core/dev.c:6681
napi_complete include/linux/netdevice.h:589 [inline]
tun_get_user+0x5953/0x6d70 drivers/net/tun.c:1924
tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999
do_iter_readv_writev+0x9e1/0xc20 fs/read_write.c:-1
vfs_writev+0x52a/0x1500 fs/read_write.c:1057
do_writev+0x1b5/0x580 fs/read_write.c:1103
__do_sys_writev fs/read_write.c:1171 [inline]
__se_sys_writev fs/read_write.c:1168 [inline]
__x64_sys_writev+0x99/0xf0 fs/read_write.c:1168
x64_sys_call+0x24b1/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:21
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
slab_post_alloc_hook mm/slub.c:4977 [inline]
slab_alloc_node mm/slub.c:5280 [inline]
kmem_cache_alloc_node_noprof+0x989/0x16b0 mm/slub.c:5332
kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:579
__alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
napi_alloc_skb+0xc1/0x740 net/core/skbuff.c:812
napi_get_frags+0xab/0x250 net/core/gro.c:681
tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
tun_get_user+0x1352/0x6d70 drivers/net/tun.c:1784
tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999
do_iter_readv_writev+0x9e1/0xc20 fs/read_write.c:-1
vfs_writev+0x52a/0x1500 fs/read_write.c:1057
do_writev+0x1b5/0x580 fs/read_write.c:1103
__do_sys_writev fs/read_write.c:1171 [inline]
__se_sys_writev fs/read_write.c:1168 [inline]
__x64_sys_writev+0x99/0xf0 fs/read_write.c:1168
x64_sys_call+0x24b1/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:21
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 6553 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(none)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
=====================================================


Tested on:

commit: 4a0c9b33 Merge tag 'probes-fixes-v6.18-rc4' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123c7012580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2901a6a99b67fbcc
dashboard link: https://syzkaller.appspot.com/bug?extid=9a4fbb77c9d4aacd3388
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=104a332f980000

[HariKrishna Sagala]

#syz test

diff --git a/net/tipc/msg.c b/net/tipc/msg.c

index 76284fc538eb..eb50a9e23507 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -71,6 +71,8 @@ struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)

skb = alloc_skb_fclone(BUF_OVERHEAD + size, gfp);
if (skb) {

+ pr_info("tipc_buf_acquire\n");
+ memset(skb, 0, sizeof(struct sk_buff));
skb_reserve(skb, BUF_HEADROOM);
skb_put(skb, size);
skb->next = NULL;

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:

kernel BUG in tipc_buf_acquire

tipc: Started in network mode
tipc: Node identity 5e9377e8cc82, cluster identity 4711
tipc: tipc_buf_acquire
skbuff: skb_over_panic: text:ffffffff8fe53c01 len:76 put:76 head:0000000000000000 data:00000000000000d0 tail:0x11c end:0x0 dev:<NULL>
------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:212!
Oops: invalid opcode: 0000 [#1] SMP PTI
CPU: 0 UID: 0 PID: 6600 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(none)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025

RIP: 0010:skb_panic+0x2d3/0x340 net/core/skbuff.c:212
Code: d0 44 8b 45 cc 4c 8b 8d 58 ff ff ff 41 52 ff b5 70 ff ff ff ff b5 68 ff ff ff ff b5 60 ff ff ff e8 d2 5d ee ff 48 83 c4 20 90 <0f> 0b e8 c6 8f 69 01 48 83 7d a0 00 0f 84 6a ff ff ff 48 8b 7d c0
RSP: 0018:ffff88801f8cf0e8 EFLAGS: 00010286
RAX: 0000000000000085 RBX: ffff88811718cda0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffff88801f8cf1a0 R08: ffffea000000000f R09: 0000000000000000
R10: ffff888237c7e028 R11: ffff88823f278d40 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f26537fe6c0(0000) GS:ffff8881aaf8d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2654574620 CR3: 0000000049ab8000 CR4: 00000000003526f0
Call Trace:
<TASK>
skb_over_panic net/core/skbuff.c:217 [inline]
skb_put+0x1f5/0x250 net/core/skbuff.c:2583
tipc_buf_acquire+0x141/0x1b0 net/tipc/msg.c:77
tipc_disc_create+0x12f/0x870 net/tipc/discover.c:359
tipc_enable_bearer net/tipc/bearer.c:348 [inline]
__tipc_nl_bearer_enable+0x1f61/0x2a00 net/tipc/bearer.c:1047
__tipc_nl_compat_doit net/tipc/netlink_compat.c:371 [inline]
tipc_nl_compat_doit+0x67b/0xa10 net/tipc/netlink_compat.c:393
tipc_nl_compat_handle net/tipc/netlink_compat.c:-1 [inline]
tipc_nl_compat_recv+0x1007/0x1670 net/tipc/netlink_compat.c:1321
genl_family_rcv_msg_doit+0x338/0x3f0 net/netlink/genetlink.c:1115
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0xacf/0xc10 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x54d/0x680 net/netlink/af_netlink.c:2552
genl_rcv+0x41/0x60 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0xf04/0x12b0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x10b3/0x1250 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg+0x333/0x3d0 net/socket.c:742
____sys_sendmsg+0x7e0/0xd80 net/socket.c:2630
___sys_sendmsg+0x271/0x3b0 net/socket.c:2684
__sys_sendmsg net/socket.c:2716 [inline]
__do_sys_sendmsg net/socket.c:2721 [inline]
__se_sys_sendmsg net/socket.c:2719 [inline]
__x64_sys_sendmsg+0x211/0x3e0 net/socket.c:2719
x64_sys_call+0x1dfd/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:47

do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f265458eb69
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f26537fe038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f26547b5fa0 RCX: 00007f265458eb69
RDX: 0000000000000000 RSI: 00002000000002c0 RDI: 0000000000000006
RBP: 00007f2654611df1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f26547b5fa0 R15: 00007ffe744cefd8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:skb_panic+0x2d3/0x340 net/core/skbuff.c:212
Code: d0 44 8b 45 cc 4c 8b 8d 58 ff ff ff 41 52 ff b5 70 ff ff ff ff b5 68 ff ff ff ff b5 60 ff ff ff e8 d2 5d ee ff 48 83 c4 20 90 <0f> 0b e8 c6 8f 69 01 48 83 7d a0 00 0f 84 6a ff ff ff 48 8b 7d c0
RSP: 0018:ffff88801f8cf0e8 EFLAGS: 00010286
RAX: 0000000000000085 RBX: ffff88811718cda0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffff88801f8cf1a0 R08: ffffea000000000f R09: 0000000000000000
R10: ffff888237c7e028 R11: ffff88823f278d40 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f26537fe6c0(0000) GS:ffff8881aaf8d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2654574620 CR3: 0000000049ab8000 CR4: 00000000003526f0

Tested on:

commit: 4a0c9b33 Merge tag 'probes-fixes-v6.18-rc4' of git://g..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=17a79084580000

kernel config: https://syzkaller.appspot.com/x/.config?x=2901a6a99b67fbcc
dashboard link: https://syzkaller.appspot.com/bug?extid=9a4fbb77c9d4aacd3388
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=107a332f980000

[harikrishna]

#syz test

diff --git a/net/tipc/msg.c b/net/tipc/msg.c

index 76284fc538eb..4c22cce4be30 100644

--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -71,6 +71,8 @@ struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)

skb = alloc_skb_fclone(BUF_OVERHEAD + size, gfp);
if (skb) {

+ pr_info("tipc_buf_acquire data len: %d\n", skb->data_len);
+ memset(skb->data, 0, skb->data_len);

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:

KMSAN: uninit-value in tipc_rcv

tipc: Started in network mode

tipc: Node identity a287e0d4fc68, cluster identity 4711
tipc: tipc_buf_acquire data len: 0
tipc: Enabled bearer <eth:syzkaller0>, priority 0

=====================================================
BUG: KMSAN: uninit-value in tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
tipc_l2_rcv_msg+0x213/0x320 net/tipc/bearer.c:668
__netif_receive_skb_list_ptype net/core/dev.c:6127 [inline]
__netif_receive_skb_list_core+0x133e/0x16b0 net/core/dev.c:6169
__netif_receive_skb_list net/core/dev.c:6221 [inline]
netif_receive_skb_list_internal+0xee7/0x1530 net/core/dev.c:6312
gro_normal_list include/net/gro.h:524 [inline]
gro_flush_normal include/net/gro.h:532 [inline]
napi_complete_done+0x3fb/0x7d0 net/core/dev.c:6681
napi_complete include/linux/netdevice.h:589 [inline]
tun_get_user+0x5953/0x6d70 drivers/net/tun.c:1924
tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999
do_iter_readv_writev+0x9e1/0xc20 fs/read_write.c:-1
vfs_writev+0x52a/0x1500 fs/read_write.c:1057
do_writev+0x1b5/0x580 fs/read_write.c:1103
__do_sys_writev fs/read_write.c:1171 [inline]
__se_sys_writev fs/read_write.c:1168 [inline]
__x64_sys_writev+0x99/0xf0 fs/read_write.c:1168
x64_sys_call+0x24b1/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:21

do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
slab_post_alloc_hook mm/slub.c:4977 [inline]
slab_alloc_node mm/slub.c:5280 [inline]
kmem_cache_alloc_node_noprof+0x989/0x16b0 mm/slub.c:5332
kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:579
__alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
napi_alloc_skb+0xc1/0x740 net/core/skbuff.c:812
napi_get_frags+0xab/0x250 net/core/gro.c:681
tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
tun_get_user+0x1352/0x6d70 drivers/net/tun.c:1784
tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999
do_iter_readv_writev+0x9e1/0xc20 fs/read_write.c:-1
vfs_writev+0x52a/0x1500 fs/read_write.c:1057
do_writev+0x1b5/0x580 fs/read_write.c:1103
__do_sys_writev fs/read_write.c:1171 [inline]
__se_sys_writev fs/read_write.c:1168 [inline]
__x64_sys_writev+0x99/0xf0 fs/read_write.c:1168
x64_sys_call+0x24b1/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:21

do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 6569 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(none)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025

=====================================================

Tested on:

commit: 4a0c9b33 Merge tag 'probes-fixes-v6.18-rc4' of git://g..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=1365ca92580000

kernel config: https://syzkaller.appspot.com/x/.config?x=2901a6a99b67fbcc
dashboard link: https://syzkaller.appspot.com/bug?extid=9a4fbb77c9d4aacd3388
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=13631114580000