[syzbot] [hams?] KMSAN: uninit-value in nr_route_frame

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f5837722ffec Merge tag 'mm-hotfixes-stable-2023-12-27-15-0..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11b07dcee80000
kernel config: https://syzkaller.appspot.com/x/.config?x=d4130d4bb32c48ef
dashboard link: https://syzkaller.appspot.com/bug?extid=f770ce3566e60e5573ac
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d07cf63b077e/disk-f5837722.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/444db9c07b7a/vmlinux-f5837722.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7ed4733987d7/bzImage-f5837722.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f770ce...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in nr_route_frame+0x4a9/0xfc0 net/netrom/nr_route.c:787
nr_route_frame+0x4a9/0xfc0 net/netrom/nr_route.c:787
nr_xmit+0x5a/0x1c0 net/netrom/nr_dev.c:144
__netdev_start_xmit include/linux/netdevice.h:4940 [inline]
netdev_start_xmit include/linux/netdevice.h:4954 [inline]
xmit_one net/core/dev.c:3548 [inline]
dev_hard_start_xmit+0x247/0xa10 net/core/dev.c:3564
__dev_queue_xmit+0x33b8/0x5130 net/core/dev.c:4349
dev_queue_xmit include/linux/netdevice.h:3134 [inline]
raw_sendmsg+0x654/0xc10 net/ieee802154/socket.c:299
ieee802154_sock_sendmsg+0x91/0xc0 net/ieee802154/socket.c:96
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
__sys_sendmsg net/socket.c:2667 [inline]
__do_sys_sendmsg net/socket.c:2676 [inline]
__se_sys_sendmsg net/socket.c:2674 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
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:6334
sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2780
sock_alloc_send_skb include/net/sock.h:1884 [inline]
raw_sendmsg+0x36d/0xc10 net/ieee802154/socket.c:282
ieee802154_sock_sendmsg+0x91/0xc0 net/ieee802154/socket.c:96
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
__sys_sendmsg net/socket.c:2667 [inline]
__do_sys_sendmsg net/socket.c:2676 [inline]
__se_sys_sendmsg net/socket.c:2674 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

CPU: 1 PID: 9891 Comm: syz-executor.5 Not tainted 6.7.0-rc7-syzkaller-00016-gf5837722ffec #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
=====================================================


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 04b8076df253 Merge tag 'firewire-fixes-6.8-rc7' of git://g..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15ccc1a2180000
kernel config: https://syzkaller.appspot.com/x/.config?x=80c7a82a572c0de3

dashboard link: https://syzkaller.appspot.com/bug?extid=f770ce3566e60e5573ac
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=12918b32180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16b3efac180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a4610b1ff2a7/disk-04b8076d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/991e9d902d39/vmlinux-04b8076d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a5b8e8e98121/bzImage-04b8076d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f770ce...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in nr_route_frame+0x4a9/0xfc0 net/netrom/nr_route.c:787
nr_route_frame+0x4a9/0xfc0 net/netrom/nr_route.c:787
nr_xmit+0x5a/0x1c0 net/netrom/nr_dev.c:144

__netdev_start_xmit include/linux/netdevice.h:4980 [inline]
netdev_start_xmit include/linux/netdevice.h:4994 [inline]
xmit_one net/core/dev.c:3547 [inline]
dev_hard_start_xmit+0x244/0xa10 net/core/dev.c:3563
__dev_queue_xmit+0x33ed/0x51c0 net/core/dev.c:4351
dev_queue_xmit include/linux/netdevice.h:3171 [inline]
raw_sendmsg+0x64e/0xc10 net/ieee802154/socket.c:299

ieee802154_sock_sendmsg+0x91/0xc0 net/ieee802154/socket.c:96
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
__sys_sendmsg net/socket.c:2667 [inline]
__do_sys_sendmsg net/socket.c:2676 [inline]
__se_sys_sendmsg net/socket.c:2674 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
do_syscall_x64 arch/x86/entry/common.c:52 [inline]

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

entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:

slab_post_alloc_hook mm/slub.c:3819 [inline]
slab_alloc_node mm/slub.c:3860 [inline]
kmem_cache_alloc_node+0x5cb/0xbc0 mm/slub.c:3903
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560
__alloc_skb+0x352/0x790 net/core/skbuff.c:651
alloc_skb include/linux/skbuff.h:1296 [inline]
alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6394
sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2783
sock_alloc_send_skb include/net/sock.h:1855 [inline]
raw_sendmsg+0x367/0xc10 net/ieee802154/socket.c:282

ieee802154_sock_sendmsg+0x91/0xc0 net/ieee802154/socket.c:96
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
__sys_sendmsg net/socket.c:2667 [inline]
__do_sys_sendmsg net/socket.c:2676 [inline]
__se_sys_sendmsg net/socket.c:2674 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
do_syscall_x64 arch/x86/entry/common.c:52 [inline]

do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

CPU: 0 PID: 5044 Comm: syz-executor263 Not tainted 6.8.0-rc6-syzkaller-00250-g04b8076df253 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
=====================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[Edward Adam Davis]

please test uninit-value in nr_route_frame

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

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index edbbef563d4d..c8662be35000 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -656,6 +656,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
* to allow max possible filling before reallocation.
*/
prefetchw(data + SKB_WITH_OVERHEAD(size));
+ memset(data, 0, sizeof(*data));

/*
* Only clear those fields we need to clear, not those that we will

[syzbot]

Hello,

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

__alloc_skb+0x33d/0x7a0 net/core/skbuff.c:651
alloc_skb include/linux/skbuff.h:1296 [inline]
alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6395

sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2783
sock_alloc_send_skb include/net/sock.h:1855 [inline]
raw_sendmsg+0x367/0xc10 net/ieee802154/socket.c:282
ieee802154_sock_sendmsg+0x91/0xc0 net/ieee802154/socket.c:96
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
__sys_sendmsg net/socket.c:2667 [inline]
__do_sys_sendmsg net/socket.c:2676 [inline]
__se_sys_sendmsg net/socket.c:2674 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

CPU: 1 PID: 5501 Comm: syz-executor.0 Not tainted 6.8.0-rc6-syzkaller-g04b8076df253-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
=====================================================

Tested on:

commit: 04b8076d Merge tag 'firewire-fixes-6.8-rc7' of git://g..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=149cd06c180000

kernel config: https://syzkaller.appspot.com/x/.config?x=80c7a82a572c0de3
dashboard link: https://syzkaller.appspot.com/bug?extid=f770ce3566e60e5573ac
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1666dc36180000

[Edward Adam Davis]

please test uninit-value in nr_route_frame

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

diff --git a/net/core/skbuff.c b/net/core/skbuff.c

index edbbef563d4d..5ca5a608daec 100644

--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -656,6 +656,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
* to allow max possible filling before reallocation.
*/
prefetchw(data + SKB_WITH_OVERHEAD(size));

+ memset(data, 0, size);

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+f770ce...@syzkaller.appspotmail.com

Tested on:

commit: 04b8076d Merge tag 'firewire-fixes-6.8-rc7' of git://g..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

console output: https://syzkaller.appspot.com/x/log.txt?x=17b893ce180000

kernel config: https://syzkaller.appspot.com/x/.config?x=80c7a82a572c0de3
dashboard link: https://syzkaller.appspot.com/bug?extid=f770ce3566e60e5573ac
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16d811a2180000

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

[Edward Adam Davis]

[Syzbot reported]

[Fix]
Let's clear all skb data at alloc time.

Reported-and-tested-by: syzbot+f770ce...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
net/core/skbuff.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index edbbef563d4d..5ca5a608daec 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -656,6 +656,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
* to allow max possible filling before reallocation.
*/
prefetchw(data + SKB_WITH_OVERHEAD(size));
+ memset(data, 0, size);

/*
* Only clear those fields we need to clear, not those that we will

--
2.43.0

[Eric Dumazet]

This can not be serious.

>
> Reported-and-tested-by: syzbot+f770ce...@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <ead...@qq.com>

Fix net/netrom instead.

[Edward Adam Davis]

Reported-and-tested-by: syzbot+f770ce...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>

[Eric Dumazet]

On Mon, Mar 4, 2024 at 6:05 AM Edward Adam Davis <ead...@qq.com> wrote:
>
> [Syzbot reported]
>

> [Fix]
> Let's clear all skb data at alloc time.
>
> Reported-and-tested-by: syzbot+f770ce...@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <ead...@qq.com>
> ---
> net/core/skbuff.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index edbbef563d4d..5ca5a608daec 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -656,6 +656,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
> * to allow max possible filling before reallocation.
> */
> prefetchw(data + SKB_WITH_OVERHEAD(size));
> + memset(data, 0, size);

We are not going to accept such a change, for obvious performance reasons.

Instead, please fix net/netrom/nr_route.c

Thank you.