linux-kernel - Re: [syzbot] [ppp?] KMSAN: uninit-value in ppp_sync

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Message-ID: <67b0af39.050a0220.6f0b7.000d.GAE@google.com>
Date: Sat, 15 Feb 2025 07:14:01 -0800
From: syzbot <syzbot+29fc8991b0ecb186cf40@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, purvayeshi550@...il.com, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [ppp?] KMSAN: uninit-value in ppp_sync_send (2)

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