[syzbot] [ppp?] KMSAN: uninit-value in ppp_sync_send (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9946eaf552b1 Merge tag 'hardening-v6.14-rc2' of git://git...
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=131dabdf980000
kernel config: https://syzkaller.appspot.com/x/.config?x=f20bce78db15972a
dashboard link: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40
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=17b142a4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14167df8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/955ec208b383/disk-9946eaf5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ccb7613686d1/vmlinux-9946eaf5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/10b92522362a/bzImage-9946eaf5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+29fc89...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in ppp_sync_txmunge drivers/net/ppp/ppp_synctty.c:516 [inline]
BUG: KMSAN: uninit-value in ppp_sync_send+0x21c/0xb00 drivers/net/ppp/ppp_synctty.c:568
ppp_sync_txmunge drivers/net/ppp/ppp_synctty.c:516 [inline]
ppp_sync_send+0x21c/0xb00 drivers/net/ppp/ppp_synctty.c:568
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:1122
__release_sock+0x1da/0x330 net/core/sock.c:3106
release_sock+0x6b/0x250 net/core/sock.c:3660
pppoe_sendmsg+0xb35/0xc50 drivers/net/ppp/pppoe.c:903
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:733
____sys_sendmsg+0x903/0xb60 net/socket.c:2573
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2627
__sys_sendmmsg+0x2ff/0x880 net/socket.c:2716
__do_sys_sendmmsg net/socket.c:2743 [inline]
__se_sys_sendmmsg net/socket.c:2740 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2740
x64_sys_call+0x33c2/0x3c30 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:4121 [inline]
slab_alloc_node mm/slub.c:4164 [inline]
kmem_cache_alloc_node_noprof+0x907/0xe00 mm/slub.c:4216
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:587
__alloc_skb+0x363/0x7b0 net/core/skbuff.c:678
alloc_skb include/linux/skbuff.h:1331 [inline]
sock_wmalloc+0xfe/0x1a0 net/core/sock.c:2746
pppoe_sendmsg+0x385/0xc50 drivers/net/ppp/pppoe.c:867
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:733
____sys_sendmsg+0x903/0xb60 net/socket.c:2573
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2627
__sys_sendmmsg+0x2ff/0x880 net/socket.c:2716
__do_sys_sendmmsg net/socket.c:2743 [inline]
__se_sys_sendmmsg net/socket.c:2740 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2740
x64_sys_call+0x33c2/0x3c30 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: 5806 Comm: syz-executor201 Not tainted 6.14.0-rc1-syzkaller-00235-g9946eaf552b1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
=====================================================


---
This report is generated by a bot. It may contain errors.
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If the report is already addressed, let syzbot know by replying with:
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[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject:
Author: purvay...@gmail.com

#syz test

[syzbot]

Hello,

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

drivers/net/ppp/ppp_synctty.c:502:43: error: too many arguments to function call, expected single argument 'length', have 2 arguments


Tested on:

commit: 7ff71e6d Merge tag 'alpha-fixes-v6.14-rc2' of git://gi..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=f20bce78db15972a
dashboard link: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=13c5dce4580000

[syzbot]

[syzbot]

Hello,

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

drivers/net/ppp/ppp_synctty.c:502:23: error: initializer element is not a compile-time constant

Tested on:

commit: 7ff71e6d Merge tag 'alpha-fixes-v6.14-rc2' of git://gi..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=f20bce78db15972a
dashboard link: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=124f99a4580000

[syzbot]

[syzbot]

Hello,

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

=====================================================
BUG: KMSAN: uninit-value in ppp_sync_txmunge drivers/net/ppp/ppp_synctty.c:521 [inline]
BUG: KMSAN: uninit-value in ppp_sync_send+0x2dc/0xc60 drivers/net/ppp/ppp_synctty.c:573
ppp_sync_txmunge drivers/net/ppp/ppp_synctty.c:521 [inline]
ppp_sync_send+0x2dc/0xc60 drivers/net/ppp/ppp_synctty.c:573

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:1122
__release_sock+0x1da/0x330 net/core/sock.c:3106
release_sock+0x6b/0x250 net/core/sock.c:3660
pppoe_sendmsg+0xb35/0xc50 drivers/net/ppp/pppoe.c:903
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:733
____sys_sendmsg+0x903/0xb60 net/socket.c:2573
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2627
__sys_sendmmsg+0x2ff/0x880 net/socket.c:2716
__do_sys_sendmmsg net/socket.c:2743 [inline]
__se_sys_sendmmsg net/socket.c:2740 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2740
x64_sys_call+0x33c2/0x3c30 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:

__alloc_frozen_pages_noprof+0x9a7/0xe00 mm/page_alloc.c:4762
__alloc_pages_noprof+0x41/0xd0 mm/page_alloc.c:4773
__page_frag_cache_refill+0x51/0x200 mm/page_frag_cache.c:59
__page_frag_alloc_align+0xc9/0x630 mm/page_frag_cache.c:103
page_frag_alloc include/linux/page_frag_cache.h:56 [inline]
__netdev_alloc_skb+0x6ab/0x720 net/core/skbuff.c:762
netdev_alloc_skb include/linux/skbuff.h:3410 [inline]
dev_alloc_skb include/linux/skbuff.h:3423 [inline]
ppp_sync_txmunge drivers/net/ppp/ppp_synctty.c:508 [inline]
ppp_sync_send+0xf1/0xc60 drivers/net/ppp/ppp_synctty.c:573

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:1122
__release_sock+0x1da/0x330 net/core/sock.c:3106
release_sock+0x6b/0x250 net/core/sock.c:3660
pppoe_sendmsg+0xb35/0xc50 drivers/net/ppp/pppoe.c:903
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:733
____sys_sendmsg+0x903/0xb60 net/socket.c:2573
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2627
__sys_sendmmsg+0x2ff/0x880 net/socket.c:2716
__do_sys_sendmmsg net/socket.c:2743 [inline]
__se_sys_sendmmsg net/socket.c:2740 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2740
x64_sys_call+0x33c2/0x3c30 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: 6764 Comm: syz.0.16 Not tainted 6.14.0-rc2-syzkaller-00259-g7ff71e6d9239-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
=====================================================

Tested on:

commit: 7ff71e6d Merge tag 'alpha-fixes-v6.14-rc2' of git://gi..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=167c59a4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=92e8820bdc5f2bf2

dashboard link: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=154ee7df980000

[syzbot]

[syzbot]

Hello,

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

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

BUG: KMSAN: uninit-value in ppp_sync_txmunge drivers/net/ppp/ppp_synctty.c:517 [inline]
BUG: KMSAN: uninit-value in ppp_sync_send+0x21c/0xb00 drivers/net/ppp/ppp_synctty.c:569
ppp_sync_txmunge drivers/net/ppp/ppp_synctty.c:517 [inline]
ppp_sync_send+0x21c/0xb00 drivers/net/ppp/ppp_synctty.c:569

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:1122
__release_sock+0x1da/0x330 net/core/sock.c:3106
release_sock+0x6b/0x250 net/core/sock.c:3660
pppoe_sendmsg+0xb35/0xc50 drivers/net/ppp/pppoe.c:903
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:733
____sys_sendmsg+0x903/0xb60 net/socket.c:2573
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2627
__sys_sendmmsg+0x2ff/0x880 net/socket.c:2716
__do_sys_sendmmsg net/socket.c:2743 [inline]
__se_sys_sendmmsg net/socket.c:2740 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2740
x64_sys_call+0x33c2/0x3c30 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:4121 [inline]
slab_alloc_node mm/slub.c:4164 [inline]
kmem_cache_alloc_node_noprof+0x907/0xe00 mm/slub.c:4216
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:587
__alloc_skb+0x363/0x7b0 net/core/skbuff.c:678
alloc_skb include/linux/skbuff.h:1331 [inline]
sock_wmalloc+0xfe/0x1a0 net/core/sock.c:2746
pppoe_sendmsg+0x385/0xc50 drivers/net/ppp/pppoe.c:867

sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:733
____sys_sendmsg+0x903/0xb60 net/socket.c:2573
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2627
__sys_sendmmsg+0x2ff/0x880 net/socket.c:2716
__do_sys_sendmmsg net/socket.c:2743 [inline]
__se_sys_sendmmsg net/socket.c:2740 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2740
x64_sys_call+0x33c2/0x3c30 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: 6825 Comm: syz.0.16 Not tainted 6.14.0-rc2-syzkaller-00281-g496659003dac-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
=====================================================


Tested on:

commit: 49665900 Merge tag 'i2c-for-6.14-rc3' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1177e7df980000

kernel config: https://syzkaller.appspot.com/x/.config?x=92e8820bdc5f2bf2
dashboard link: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=14dacbf8580000

[syzbot]

[syzbot]

Hello,

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

Reported-by: syzbot+29fc89...@syzkaller.appspotmail.com
Tested-by: syzbot+29fc89...@syzkaller.appspotmail.com

Tested on:

commit: 49665900 Merge tag 'i2c-for-6.14-rc3' of git://git.ker..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=1380b9b0580000

kernel config: https://syzkaller.appspot.com/x/.config?x=92e8820bdc5f2bf2
dashboard link: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=118f39b0580000

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

[Arnaud Lecomte]

#syz test: https://github.com/ArnaudLcm/linux bounds-checking-txmung

[syzbot]

> Author: con...@arnaud-lcm.com
>
> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

want either no args or 2 args (repo, branch), got 5

>
> diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c
> index 644e99fc3623..520d895acc60 100644
> --- a/drivers/net/ppp/ppp_synctty.c
> +++ b/drivers/net/ppp/ppp_synctty.c
> @@ -506,6 +506,11 @@ ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb)
> unsigned char *data;
> int islcp;
>
> + /* Ensure we can safely access protocol field and LCP code */
> + if (!skb || !pskb_may_pull(skb, 3)) {
> + kfree_skb(skb);
> + return NULL;
> + }
> data = skb->data;
> proto = get_unaligned_be16(data);

[Arnaud Lecomte]

Author: con...@arnaud-lcm.com

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

[Arnaud Lecomte]

Author: con...@arnaud-lcm.com

#syz test

[syzbot]

Hello,

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

failed to checkout kernel repo https://github.com/ArnaudLcm/linux/bounds-checking-txmung: failed to run ["git" "fetch" "--force" "98936a0cc8cd68334b039c881b39b10e6f0d7c99" "bounds-checking-txmung"]: exit status 128
fatal: couldn't find remote ref bounds-checking-txmung



Tested on:

commit: [unknown
git tree: https://github.com/ArnaudLcm/linux bounds-checking-txmung
kernel config: https://syzkaller.appspot.com/x/.config?x=f20bce78db15972a

dashboard link: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40
compiler:

Note: no patches were applied.

[syzbot]

Hello,

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

Reported-by: syzbot+29fc89...@syzkaller.appspotmail.com
Tested-by: syzbot+29fc89...@syzkaller.appspotmail.com

Tested on:

commit: 0af2f6be Linux 6.15-rc1
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f81b4c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2a6e21b5ffe4f6eb
dashboard link: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40

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

patch: https://syzkaller.appspot.com/x/patch.diff?x=105b3b4c580000