KMSAN: uninit-value in ppp_sync_send (2)

Status: fixed on 2025/06/10 16:19
Subsystems: ppp
[Documentation on labels]
Reported-by: syzbot+29fc8991b0ecb186cf40@syzkaller.appspotmail.com
Fix commit: aabc6596ffb3 net: ppp: Add bound checking for skb data on ppp_sync_txmung
First crash: 532d, last: 518d
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
[PATCH v2] net: ppp: Add bound checking for skb d on ppp_sync_txmung 4 (4) 2025/04/10 12:19
[PATCH] net: ppp: Add bound checking for skb d on ppp_sync_txmung 3 (3) 2025/04/08 15:58
[syzbot] [ppp?] KMSAN: uninit-value in ppp_sync_send (2) 3 (12) 2025/04/07 14:54
[PATCH] ppp: Prevent out-of-bounds access in ppp_sync_txmunge 5 (5) 2025/02/25 06:20
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KMSAN: uninit-value in ppp_sync_send ppp 7 7 649d 650d 0/29 auto-obsoleted due to no activity on 2025/01/21 06:58
▶ ▼ Last patch testing requests (8)
Created Duration User Patch Repo Result
2025/04/07 14:17 28m contact@arnaud-lcm.com patch upstream OK log
2025/04/07 14:06 0m contact@arnaud-lcm.com https://github.com/ArnaudLcm/linux bounds-checking-txmung error
2025/02/23 22:01 23m retest repro upstream report log
2025/02/15 19:35 29m purvayeshi550@gmail.com patch upstream OK log
2025/02/15 18:42 30m purvayeshi550@gmail.com patch upstream report log
2025/02/15 14:31 23m purvayeshi550@gmail.com patch upstream report log
2025/02/15 12:33 11m purvayeshi550@gmail.com patch upstream error
2025/02/15 07:58 7m purvayeshi550@gmail.com patch upstream error

Sample crash report:
=====================================================
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
=====================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/02/09 21:49 upstream 9946eaf552b1 ef44b750 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ppp_sync_send
2025/02/09 18:23 upstream 9946eaf552b1 ef44b750 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ppp_sync_send
2025/02/09 18:23 upstream 9946eaf552b1 ef44b750 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ppp_sync_send
* Struck through repros no longer work on HEAD.