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Date:   Wed, 29 Nov 2023 02:00:33 -0800
Message-ID: <0000000000001fc0bf060b479b58@google.com>
Subject: [syzbot] [net?] KMSAN: uninit-value in ipgre_xmit
From:   syzbot <syzbot+2cb7b1bd08dc77ae7f89@syzkaller.appspotmail.com>
To:     davem@davemloft.net, dsahern@kernel.org, edumazet@google.com,
        kuba@kernel.org, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, pabeni@redhat.com,
        syzkaller-bugs@googlegroups.com
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Hello,

syzbot found the following issue on:

HEAD commit:    18d46e76d7c2 Merge tag 'for-6.7-rc3-tag' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1412e7e8e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f711bc2a7eb1db25
dashboard link: https://syzkaller.appspot.com/bug?extid=2cb7b1bd08dc77ae7f89
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cb96093de792/disk-18d46e76.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/630ca4e2d778/vmlinux-18d46e76.xz
kernel image: https://storage.googleapis.com/syzbot-assets/65573a727973/bzImage-18d46e76.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2cb7b1bd08dc77ae7f89@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in __gre_xmit net/ipv4/ip_gre.c:469 [inline]
BUG: KMSAN: uninit-value in ipgre_xmit+0xdc2/0xe20 net/ipv4/ip_gre.c:662
 __gre_xmit net/ipv4/ip_gre.c:469 [inline]
 ipgre_xmit+0xdc2/0xe20 net/ipv4/ip_gre.c:662
 __netdev_start_xmit include/linux/netdevice.h:4940 [inline]
 netdev_start_xmit include/linux/netdevice.h:4954 [inline]
 xmit_one net/core/dev.c:3545 [inline]
 dev_hard_start_xmit+0x247/0xa10 net/core/dev.c:3561
 __dev_queue_xmit+0x33b8/0x5130 net/core/dev.c:4346
 dev_queue_xmit include/linux/netdevice.h:3134 [inline]
 __bpf_tx_skb net/core/filter.c:2133 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2163 [inline]
 __bpf_redirect+0xdd7/0x1600 net/core/filter.c:2186
 ____bpf_clone_redirect net/core/filter.c:2457 [inline]
 bpf_clone_redirect+0x328/0x470 net/core/filter.c:2429
 ___bpf_prog_run+0x2180/0xdb80 kernel/bpf/core.c:1958
 __bpf_prog_run512+0xb5/0xe0 kernel/bpf/core.c:2199
 bpf_dispatcher_nop_func include/linux/bpf.h:1196 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run include/linux/filter.h:658 [inline]
 bpf_test_run+0x482/0xb00 net/bpf/test_run.c:423
 bpf_prog_test_run_skb+0x14e5/0x1f20 net/bpf/test_run.c:1045
 bpf_prog_test_run+0x6af/0xac0 kernel/bpf/syscall.c:4040
 __sys_bpf+0x649/0xd60 kernel/bpf/syscall.c:5401
 __do_sys_bpf kernel/bpf/syscall.c:5487 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5485 [inline]
 __ia32_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5485
 do_syscall_32_irqs_on arch/x86/entry/common.c:164 [inline]
 __do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:230
 do_fast_syscall_32+0x37/0x70 arch/x86/entry/common.c:255
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:293
 entry_SYSENTER_compat_after_hwframe+0x70/0x7a

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
 pskb_expand_head+0x226/0x1a00 net/core/skbuff.c:2098
 skb_ensure_writable+0x3d3/0x460 net/core/skbuff.c:5958
 __bpf_try_make_writable net/core/filter.c:1662 [inline]
 bpf_try_make_writable net/core/filter.c:1668 [inline]
 bpf_try_make_head_writable net/core/filter.c:1676 [inline]
 ____bpf_clone_redirect net/core/filter.c:2451 [inline]
 bpf_clone_redirect+0x17f/0x470 net/core/filter.c:2429
 ___bpf_prog_run+0x2180/0xdb80 kernel/bpf/core.c:1958
 __bpf_prog_run512+0xb5/0xe0 kernel/bpf/core.c:2199
 bpf_dispatcher_nop_func include/linux/bpf.h:1196 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run include/linux/filter.h:658 [inline]
 bpf_test_run+0x482/0xb00 net/bpf/test_run.c:423
 bpf_prog_test_run_skb+0x14e5/0x1f20 net/bpf/test_run.c:1045
 bpf_prog_test_run+0x6af/0xac0 kernel/bpf/syscall.c:4040
 __sys_bpf+0x649/0xd60 kernel/bpf/syscall.c:5401
 __do_sys_bpf kernel/bpf/syscall.c:5487 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5485 [inline]
 __ia32_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5485
 do_syscall_32_irqs_on arch/x86/entry/common.c:164 [inline]
 __do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:230
 do_fast_syscall_32+0x37/0x70 arch/x86/entry/common.c:255
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:293
 entry_SYSENTER_compat_after_hwframe+0x70/0x7a

CPU: 1 PID: 8859 Comm: syz-executor.2 Not tainted 6.7.0-rc3-syzkaller-00024-g18d46e76d7c2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
=====================================================


---
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