[syzbot] [net?] KMSAN: uninit-value in __llc_lookup_established

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1c41041124bd Merge tag 'i3c/for-6.7' of git://git.kernel.o..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10429eeb680000
kernel config: https://syzkaller.appspot.com/x/.config?x=956549bd1d1e9efd
dashboard link: https://syzkaller.appspot.com/bug?extid=b5ad66046b913bc04c6f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12b6a00f680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=121471ef680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/20fd86e677f1/disk-1c410411.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ccd39cb0b7b6/vmlinux-1c410411.xz
kernel image: https://storage.googleapis.com/syzbot-assets/156fc60f97bc/bzImage-1c410411.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b5ad66...@syzkaller.appspotmail.com

syz-executor994 uses obsolete (PF_INET,SOCK_PACKET)
=====================================================
BUG: KMSAN: uninit-value in __llc_lookup_established+0xe9d/0xf90
__llc_lookup_established+0xe9d/0xf90
__llc_lookup net/llc/llc_conn.c:611 [inline]
llc_conn_handler+0x4bd/0x1360 net/llc/llc_conn.c:791
llc_rcv+0xfbb/0x14a0 net/llc/llc_input.c:206
__netif_receive_skb_one_core net/core/dev.c:5527 [inline]
__netif_receive_skb+0x1a6/0x5a0 net/core/dev.c:5641
netif_receive_skb_internal net/core/dev.c:5727 [inline]
netif_receive_skb+0x58/0x660 net/core/dev.c:5786
tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1555
tun_get_user+0x53af/0x66d0 drivers/net/tun.c:2002
tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
call_write_iter include/linux/fs.h:2020 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x8ef/0x1490 fs/read_write.c:584
ksys_write+0x20f/0x4c0 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__x64_sys_write+0x93/0xd0 fs/read_write.c:646
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Local variable daddr created at:
llc_conn_handler+0x53/0x1360 net/llc/llc_conn.c:783
llc_rcv+0xfbb/0x14a0 net/llc/llc_input.c:206

CPU: 1 PID: 5004 Comm: syz-executor994 Not tainted 6.6.0-syzkaller-14500-g1c41041124bd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
=====================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

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If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Kuniyuki Iwashima]

From: syzbot <syzbot+b5ad66...@syzkaller.appspotmail.com>
Date: Tue, 05 Dec 2023 10:25:31 -0800

llc_pdu_decode_[sd]a() initialises addr.mac only for ETH_P_802_2.
Otherwise, llc_estab_match() reads an uninit value form both [sd]addr.

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 1c41041124bd

diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c
index 0a3f5e0bec00..730561e186ce 100644
--- a/net/llc/llc_conn.c
+++ b/net/llc/llc_conn.c
@@ -780,7 +780,7 @@ static struct sock *llc_create_incoming_sock(struct sock *sk,

void llc_conn_handler(struct llc_sap *sap, struct sk_buff *skb)
{
- struct llc_addr saddr, daddr;
+ struct llc_addr saddr = {}, daddr = {};
struct sock *sk;

llc_pdu_decode_sa(skb, saddr.mac);

[Edward Adam Davis]

please test uninit-value in __llc_lookup_established

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 1c41041124bd

diff --git a/net/llc/llc_input.c b/net/llc/llc_input.c
index 51bccfb00a9c..58e0b8ab41b7 100644
--- a/net/llc/llc_input.c
+++ b/net/llc/llc_input.c
@@ -126,6 +126,7 @@ static inline int llc_fixup_skb(struct sk_buff *skb)

skb->transport_header += llc_len;
skb_pull(skb, llc_len);
+ printk("3sp: %d\n", skb->protocol);
if (skb->protocol == htons(ETH_P_802_2)) {
__be16 pdulen;
s32 data_size;
@@ -141,7 +142,8 @@ static inline int llc_fixup_skb(struct sk_buff *skb)
return 0;
if (unlikely(pskb_trim_rcsum(skb, data_size)))
return 0;
- }
+ } else
+ return 0;
return 1;
}

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index afa5497f7c35..bff910513fc3 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1900,6 +1900,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
skb->protocol = eth_type_trans(skb, tun->dev);
break;
}
+ printk("sp: %d\n", skb->protocol);

/* copy skb_ubuf_info for callback when skb has no error */
if (zerocopy) {
@@ -1999,6 +2000,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,

local_bh_enable();
} else if (!IS_ENABLED(CONFIG_4KSTACKS)) {
+ printk("2sp: %d\n", skb->protocol);
tun_rx_batched(tun, tfile, skb, more);
} else {
netif_rx(skb);

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+b5ad66...@syzkaller.appspotmail.com

Tested on:

commit: 1c410411 Merge tag 'i3c/for-6.7' of git://git.kernel.o..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1577c0d4e80000

kernel config: https://syzkaller.appspot.com/x/.config?x=956549bd1d1e9efd
dashboard link: https://syzkaller.appspot.com/bug?extid=b5ad66046b913bc04c6f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=13fa938ce80000

Note: testing is done by a robot and is best-effort only.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+b5ad66...@syzkaller.appspotmail.com

Tested on:

commit: 1c410411 Merge tag 'i3c/for-6.7' of git://git.kernel.o..

git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=11b6743ce80000

kernel config: https://syzkaller.appspot.com/x/.config?x=956549bd1d1e9efd
dashboard link: https://syzkaller.appspot.com/bug?extid=b5ad66046b913bc04c6f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=141ceb9ae80000

[Edward Adam Davis]

llc only supports ETH_P_802_2 protocol, so drop the skb when the protocol is
not it.

Reported-by: syzbot+b5ad66...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
net/llc/llc_input.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/llc/llc_input.c b/net/llc/llc_input.c
index 51bccfb00a9c..16b2c57f38c2 100644
--- a/net/llc/llc_input.c
+++ b/net/llc/llc_input.c
@@ -141,7 +141,8 @@ static inline int llc_fixup_skb(struct sk_buff *skb)

return 0;
if (unlikely(pskb_trim_rcsum(skb, data_size)))
return 0;
- }
+ } else
+ return 0;
return 1;
}

--
2.43.0

[Kuniyuki Iwashima]

From: Edward Adam Davis <ead...@qq.com>
Date: Wed, 6 Dec 2023 09:55:15 +0800

> llc only supports ETH_P_802_2 protocol, so drop the skb when the protocol is
> not it.

This is not true. ETH_P_TR_802_2 is also processed by llc_rcv().

Let me post this formally.
https://lore.kernel.org/netdev/20231206005340...@amazon.com/

[Edward Adam Davis]

please test uninit-value in __llc_lookup_established

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 1c41041124bd

diff --git a/net/llc/llc_input.c b/net/llc/llc_input.c
index 51bccfb00a9c..58e0b8ab41b7 100644
--- a/net/llc/llc_input.c
+++ b/net/llc/llc_input.c

@@ -126,6 +126,7 @@ static inline int llc_fixup_skb(struct sk_buff *skb)

skb->transport_header += llc_len;
skb_pull(skb, llc_len);

+ printk("3sp: %d, %d, %d\n", skb->protocol, htons(ETH_P_802_2), htons(ETH_P_TR_802_2));

if (skb->protocol == htons(ETH_P_802_2)) {
__be16 pdulen;
s32 data_size;

@@ -141,7 +142,8 @@ static inline int llc_fixup_skb(struct sk_buff *skb)

return 0;
if (unlikely(pskb_trim_rcsum(skb, data_size)))
return 0;
- }

+ } else if (skb->protocol != htons(ETH_P_TR_802_2))

[syzbot]

Hello,

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

syz-executor.0 uses obsolete (PF_INET,SOCK_PACKET)
3sp: 4352, 1024, 4352

=====================================================
BUG: KMSAN: uninit-value in __llc_lookup_established+0xe9d/0xf90
__llc_lookup_established+0xe9d/0xf90
__llc_lookup net/llc/llc_conn.c:611 [inline]
llc_conn_handler+0x4bd/0x1360 net/llc/llc_conn.c:791

llc_rcv+0x105b/0x1520 net/llc/llc_input.c:208

__netif_receive_skb_one_core net/core/dev.c:5527 [inline]
__netif_receive_skb+0x1a6/0x5a0 net/core/dev.c:5641
netif_receive_skb_internal net/core/dev.c:5727 [inline]
netif_receive_skb+0x58/0x660 net/core/dev.c:5786
tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1555
tun_get_user+0x53af/0x66d0 drivers/net/tun.c:2002
tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
call_write_iter include/linux/fs.h:2020 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x8ef/0x1490 fs/read_write.c:584
ksys_write+0x20f/0x4c0 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__x64_sys_write+0x93/0xd0 fs/read_write.c:646
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Local variable daddr created at:
llc_conn_handler+0x53/0x1360 net/llc/llc_conn.c:783

llc_rcv+0x105b/0x1520 net/llc/llc_input.c:208

CPU: 1 PID: 5474 Comm: syz-executor.0 Not tainted 6.6.0-syzkaller-14500-g1c41041124bd-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
=====================================================

Tested on:

commit: 1c410411 Merge tag 'i3c/for-6.7' of git://git.kernel.o..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

console output: https://syzkaller.appspot.com/x/log.txt?x=148a49b4e80000

kernel config: https://syzkaller.appspot.com/x/.config?x=956549bd1d1e9efd
dashboard link: https://syzkaller.appspot.com/bug?extid=b5ad66046b913bc04c6f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16c0649ce80000

[Edward Adam Davis]

please test uninit-value in __llc_lookup_established

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 1c41041124bd

diff --git a/include/net/llc_pdu.h b/include/net/llc_pdu.h
index 7e73f8e5e497..cba149476e41 100644
--- a/include/net/llc_pdu.h
+++ b/include/net/llc_pdu.h
@@ -262,7 +262,8 @@ static inline void llc_pdu_header_init(struct sk_buff *skb, u8 type,
*/
static inline void llc_pdu_decode_sa(struct sk_buff *skb, u8 *sa)
{
- if (skb->protocol == htons(ETH_P_802_2))
+ if (skb->protocol == htons(ETH_P_802_2) ||
+ skb->protocol == htons(ETH_P_TR_802_2))
memcpy(sa, eth_hdr(skb)->h_source, ETH_ALEN);
}

@@ -275,7 +276,8 @@ static inline void llc_pdu_decode_sa(struct sk_buff *skb, u8 *sa)
*/
static inline void llc_pdu_decode_da(struct sk_buff *skb, u8 *da)
{
- if (skb->protocol == htons(ETH_P_802_2))
+ if (skb->protocol == htons(ETH_P_802_2) ||
+ skb->protocol == htons(ETH_P_TR_802_2))
memcpy(da, eth_hdr(skb)->h_dest, ETH_ALEN);
}

diff --git a/net/llc/llc_input.c b/net/llc/llc_input.c
index 51bccfb00a9c..ed1a2b59b40c 100644
--- a/net/llc/llc_input.c
+++ b/net/llc/llc_input.c
@@ -126,7 +126,8 @@ static inline int llc_fixup_skb(struct sk_buff *skb)

skb->transport_header += llc_len;
skb_pull(skb, llc_len);

- if (skb->protocol == htons(ETH_P_802_2)) {
+ if (skb->protocol == htons(ETH_P_802_2) ||
+ skb->protocol == htons(ETH_P_TR_802_2)) {
__be16 pdulen;
s32 data_size;

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to apply patch:
checking file include/net/llc_pdu.h
checking file net/llc/llc_input.c
Hunk #1 FAILED at 126.
1 out of 1 hunk FAILED

Tested on:

commit: 1c410411 Merge tag 'i3c/for-6.7' of git://git.kernel.o..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

kernel config: https://syzkaller.appspot.com/x/.config?x=956549bd1d1e9efd
dashboard link: https://syzkaller.appspot.com/bug?extid=b5ad66046b913bc04c6f
compiler:

patch: https://syzkaller.appspot.com/x/patch.diff?x=10855d1ce80000

[Edward Adam Davis]

please test uninit-value in __llc_lookup_established

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 1c41041124bd

diff --git a/include/net/llc_pdu.h b/include/net/llc_pdu.h
index 7e73f8e5e497..cba149476e41 100644
--- a/include/net/llc_pdu.h
+++ b/include/net/llc_pdu.h
@@ -262,7 +262,8 @@ static inline void llc_pdu_header_init(struct sk_buff *skb, u8 type,
*/
static inline void llc_pdu_decode_sa(struct sk_buff *skb, u8 *sa)
{
- if (skb->protocol == htons(ETH_P_802_2))
+ if (skb->protocol == htons(ETH_P_802_2) ||
+ skb->protocol == htons(ETH_P_TR_802_2))
memcpy(sa, eth_hdr(skb)->h_source, ETH_ALEN);
}

@@ -275,7 +276,8 @@ static inline void llc_pdu_decode_sa(struct sk_buff *skb, u8 *sa)
*/
static inline void llc_pdu_decode_da(struct sk_buff *skb, u8 *da)
{
- if (skb->protocol == htons(ETH_P_802_2))
+ if (skb->protocol == htons(ETH_P_802_2) ||
+ skb->protocol == htons(ETH_P_TR_802_2))
memcpy(da, eth_hdr(skb)->h_dest, ETH_ALEN);
}

diff --git a/net/llc/llc_input.c b/net/llc/llc_input.c

index 7cac441862e2..f4f24b5d9eea 100644

--- a/net/llc/llc_input.c
+++ b/net/llc/llc_input.c
@@ -126,7 +126,8 @@ static inline int llc_fixup_skb(struct sk_buff *skb)

skb->transport_header += llc_len;
skb_pull(skb, llc_len);
- if (skb->protocol == htons(ETH_P_802_2)) {
+ if (skb->protocol == htons(ETH_P_802_2)
+ skb->protocol == htons(ETH_P_TR_802_2)) {

__be16 pdulen = eth_hdr(skb)->h_proto;
s32 data_size = ntohs(pdulen) - llc_len;

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/llc/llc_input.c:130:6: error: expected ')'

Tested on:

commit: 1c410411 Merge tag 'i3c/for-6.7' of git://git.kernel.o..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel config: https://syzkaller.appspot.com/x/.config?x=956549bd1d1e9efd
dashboard link: https://syzkaller.appspot.com/bug?extid=b5ad66046b913bc04c6f

compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1367debae80000

[Edward Adam Davis]

[syzbot]

Hello,

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

KMSAN: uninit-value in llc_rcv

syz-executor.0 uses obsolete (PF_INET,SOCK_PACKET)
=====================================================
BUG: KMSAN: uninit-value in pskb_may_pull_reason include/linux/skbuff.h:2667 [inline]
BUG: KMSAN: uninit-value in pskb_may_pull include/linux/skbuff.h:2681 [inline]
BUG: KMSAN: uninit-value in llc_fixup_skb net/llc/llc_input.c:135 [inline]
BUG: KMSAN: uninit-value in llc_rcv+0x10b9/0x1480 net/llc/llc_input.c:178
pskb_may_pull_reason include/linux/skbuff.h:2667 [inline]
pskb_may_pull include/linux/skbuff.h:2681 [inline]
llc_fixup_skb net/llc/llc_input.c:135 [inline]
llc_rcv+0x10b9/0x1480 net/llc/llc_input.c:178

__netif_receive_skb_one_core net/core/dev.c:5527 [inline]
__netif_receive_skb+0x1a6/0x5a0 net/core/dev.c:5641
netif_receive_skb_internal net/core/dev.c:5727 [inline]
netif_receive_skb+0x58/0x660 net/core/dev.c:5786
tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1555
tun_get_user+0x53af/0x66d0 drivers/net/tun.c:2002
tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
call_write_iter include/linux/fs.h:2020 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x8ef/0x1490 fs/read_write.c:584
ksys_write+0x20f/0x4c0 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__x64_sys_write+0x93/0xd0 fs/read_write.c:646
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:
slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
slab_alloc_node mm/slub.c:3478 [inline]
kmem_cache_alloc_node+0x5e9/0xb10 mm/slub.c:3523
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560
__alloc_skb+0x318/0x740 net/core/skbuff.c:651
alloc_skb include/linux/skbuff.h:1286 [inline]
alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6331
sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2780
tun_alloc_skb drivers/net/tun.c:1531 [inline]
tun_get_user+0x1e8a/0x66d0 drivers/net/tun.c:1846

tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
call_write_iter include/linux/fs.h:2020 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x8ef/0x1490 fs/read_write.c:584
ksys_write+0x20f/0x4c0 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__x64_sys_write+0x93/0xd0 fs/read_write.c:646
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

CPU: 1 PID: 5454 Comm: syz-executor.0 Not tainted 6.6.0-syzkaller-14500-g1c41041124bd-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
=====================================================

Tested on:

commit: 1c410411 Merge tag 'i3c/for-6.7' of git://git.kernel.o..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

console output: https://syzkaller.appspot.com/x/log.txt?x=111c2586e80000

kernel config: https://syzkaller.appspot.com/x/.config?x=956549bd1d1e9efd
dashboard link: https://syzkaller.appspot.com/bug?extid=b5ad66046b913bc04c6f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=140e7c4ce80000