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    SubjectRe: 2.6.25-$sha1: RIP call_for_each_cic+0x25/0x50
    On Mon, 28 Apr 2008 02:55:53 +0400 Alexey Dobriyan <adobriyan@gmail.com> wrote:

    > This happened while ~90 cross-compile jobs were running in parallel on
    > ext2/noatime partition (slowly -- much debugging was on)
    >
    >
    > general protection fault: 0000 [1] PREEMPT SMP DEBUG_PAGEALLOC
    > CPU 0
    > Modules linked in: ext2 nf_conntrack_irc ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 xt_state nf_conntrack iptable_filter ip_tables x_tables usblp uhci_hcd ehci_hcd usbcore sr_mod cdrom
    > Pid: 16483, comm: as Not tainted 2.6.25-c3bf9bc243092c53946fd6d8ebd6dc2f4e572d48 #1
    > RIP: 0010:[<ffffffff80307525>] [<ffffffff80307525>] call_for_each_cic+0x25/0x50
    > RSP: 0018:ffff810170811e58 EFLAGS: 00010202
    > RAX: 6b6b6b6b6b6b6b6b RBX: 6b6b6b6b6b6b6b6b RCX: 0000000000000000
    > RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff81010ff92000
    > RBP: ffff810170811e78 R08: 0000000000000001 R09: 0000000000000000
    > R10: 0000000000000000 R11: ffff8100010069d8 R12: ffff810138ada300
    > R13: ffffffff803075b0 R14: ffff81017fcd2000 R15: ffff81010ff92168
    > FS: 00002ac3462426f0(0000) GS:ffffffff805d0000(0000) knlGS:0000000000000000
    > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
    > CR2: 00002ab602550000 CR3: 000000013609d000 CR4: 0000000000000660
    > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
    > Process as (pid: 16483, threadinfo ffff810170810000, task ffff81010ff92000)
    > Stack: ffff810170811e88 ffff810138ada300 0000000000000010 ffff81010ff92100
    > ffff810170811e88 ffffffff80307580 ffff810170811ea8 ffffffff80302a55
    > ffff81010ff92100 ffff810138ada300 ffff810170811ec8 ffffffff80302b1f
    > Call Trace:
    > [<ffffffff80307580>] cfq_free_io_context+0x10/0x20
    > [<ffffffff80302a55>] put_io_context+0x85/0x90
    > [<ffffffff80302b1f>] exit_io_context+0x8f/0xb0
    > [<ffffffff80235d19>] do_exit+0x549/0x780
    > [<ffffffff80235f8e>] do_group_exit+0x3e/0xb0
    > [<ffffffff80236012>] sys_exit_group+0x12/0x20
    > [<ffffffff8020b6db>] system_call_after_swapgs+0x7b/0x80
    >
    >
    > Code: 84 00 00 00 00 00 55 48 89 e5 41 55 49 89 f5 41 54 49 89 fc 53 48 83 ec 08 e8 18 e1 f5 ff 49 8b 44 24 68 48 85 c0 74 1e 48 89 c3 <48> 8b 03 48 8d 73 88 4c 89 e7 0f 18 08 41 ff d5 48 8b 03 48 85
    > RIP [<ffffffff80307525>] call_for_each_cic+0x25/0x50
    > RSP <ffff810170811e58>
    > ---[ end trace ca143223eefdc828 ]---
    > Fixing recursive fault but reboot is needed!
    >
    >
    > ffffffff80307500 <call_for_each_cic>:
    > ffffffff80307500: 55 push %rbp
    > ffffffff80307501: 48 89 e5 mov %rsp,%rbp
    > ffffffff80307504: 41 55 push %r13
    > ffffffff80307506: 49 89 f5 mov %rsi,%r13
    > ffffffff80307509: 41 54 push %r12
    > ffffffff8030750b: 49 89 fc mov %rdi,%r12
    > ffffffff8030750e: 53 push %rbx
    > ffffffff8030750f: 48 83 ec 08 sub $0x8,%rsp
    > ffffffff80307513: e8 18 e1 f5 ff callq ffffffff80265630 <__rcu_read_lock>
    > ffffffff80307518: 49 8b 44 24 68 mov 0x68(%r12),%rax
    > ffffffff8030751d: 48 85 c0 test %rax,%rax
    > ffffffff80307520: 74 1e je ffffffff80307540 <call_for_each_cic+0x40>
    > ffffffff80307522: 48 89 c3 mov %rax,%rbx
    > ffffffff80307525: 48 8b 03 mov (%rbx),%rax

    use-after-free.

    > ffffffff80307528: 48 8d 73 88 lea -0x78(%rbx),%rsi
    > ffffffff8030752c: 4c 89 e7 mov %r12,%rdi
    > ffffffff8030752f: 0f 18 08 prefetcht0 (%rax)
    > ffffffff80307532: 41 ff d5 callq *%r13
    > ffffffff80307535: 48 8b 03 mov (%rbx),%rax
    > ffffffff80307538: 48 85 c0 test %rax,%rax
    > ffffffff8030753b: 48 89 c3 mov %rax,%rbx
    > ffffffff8030753e: 75 e5 jne ffffffff80307525 <call_for_each_cic+0x25>
    > ffffffff80307540: e8 2b e0 f5 ff callq ffffffff80265570 <__rcu_read_unlock>
    > ffffffff80307545: 48 83 c4 08 add $0x8,%rsp
    > ffffffff80307549: 5b pop %rbx
    > ffffffff8030754a: 41 5c pop %r12
    > ffffffff8030754c: 41 5d pop %r13
    > ffffffff8030754e: c9 leaveq
    > ffffffff8030754f: c3 retq

    cfq-iosched.c hasn't been altered (yet) so it might not be a regression.



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