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syzkaller reported crashes in IPv6 stack [1] Xin Long found that lo MTU was set to silly values. IPv6 stack reacts to changes to small MTU, by disabling itself under RTNL. But there is a window where threads not using RTNL can see a wrong device mtu. This can lead to surprises, in mld code where it is assumed the mtu is suitable. Fix this by reading device mtu once and checking IPv6 minimal MTU. [1] skbuff: skb_over_panic: text:0000000010b86b8d len:196 put:20 head:000000003b477e60 data:000000000e85441e tail:0xd4 end:0xc0 dev:lo ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:104! invalid opcode: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.15.0-rc2-mm1+ #39 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:skb_panic+0x15c/0x1f0 net/core/skbuff.c:100 RSP: 0018:ffff8801db307508 EFLAGS: 00010286 RAX: 0000000000000082 RBX: ffff8801c517e840 RCX: 0000000000000000 RDX: 0000000000000082 RSI: 1ffff1003b660e61 RDI: ffffed003b660e95 RBP: ffff8801db307570 R08: 1ffff1003b660e23 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff85bd4020 R13: ffffffff84754ed2 R14: 0000000000000014 R15: ffff8801c4e26540 FS: 0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000463610 CR3: 00000001c6698000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> skb_over_panic net/core/skbuff.c:109 [inline] skb_put+0x181/0x1c0 net/core/skbuff.c:1694 add_grhead.isra.24+0x42/0x3b0 net/ipv6/mcast.c:1695 add_grec+0xa55/0x1060 net/ipv6/mcast.c:1817 mld_send_cr net/ipv6/mcast.c:1903 [inline] mld_ifc_timer_expire+0x4d2/0x770 net/ipv6/mcast.c:2448 call_timer_fn+0x23b/0x840 kernel/time/timer.c:1320 expire_timers kernel/time/timer.c:1357 [inline] __run_timers+0x7e1/0xb60 kernel/time/timer.c:1660 run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1686 __do_softirq+0x29d/0xbb2 kernel/softirq.c:285 invoke_softirq kernel/softirq.c:365 [inline] irq_exit+0x1d3/0x210 kernel/softirq.c:405 exiting_irq arch/x86/include/asm/apic.h:540 [inline] smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052 apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:920 Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Tested-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.