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    SubjectRe: [Problem] kernel hangs at boot (bisected 892d208bcf)
    Hi Dirk,

    On Wed, Jan 18, 2012 at 07:32:59PM +0000, Dirk Gouders wrote:
    > I am not sure if you are the correct person to contact,

    I am for kmemleak :) but I'm not sure it's kmemleak's fault here.

    > but
    > I noticed a regression in Linus' master branch and bisected this to
    > commit 892d208bcf
    > "Merge tag 'kmemleak' of git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux".
    ...
    > Freeing unused kernel memory: 608k freed
    > kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
    > BUG: unable to handle kernel paging request at ffffffff818b232b
    > IP: [<ffffffff818b232b>] kmemleak_late_init+0x8a/0x8a
    > PGD 17ed067 PUD 17f1063 PMD 3c6a9063 PTE 80000000018b2163
    > Oops: 0011 [#1] SMP
    > CPU 1
    > Modules linked in:
    >
    > Pid: 1, comm: swapper/0 Not tainted 3.2.0-09104-gccb19d2 #4 Bochs Bochs
    > RIP: 0010:[<ffffffff818b232b>] [<ffffffff818b232b>] kmemleak_late_init+0x8a/0x8a
    > RSP: 0018:ffff88003fd03e58 EFLAGS: 00010282
    > RAX: 0000000000000001 RBX: ffff88003dbd2600 RCX: 0000000000000000
    > RDX: 0000000000000000 RSI: ffff88003dbd2600 RDI: 0000000000000002
    > RBP: ffff88003e015488 R08: ffff88003fd0d5c0 R09: ffff88003fd122e0
    > R10: 0000000000000400 R11: ffffffff81572da5 R12: ffffea0000f6f480
    > R13: ffffffff810aa687 R14: 0000000000000000 R15: ffff88003e31dbc8
    > FS: 0000000000000000(0000) GS:ffff88003fd00000(0000) knlGS:0000000000000000
    > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
    > CR2: ffffffff818b232b CR3: 00000000017eb000 CR4: 00000000000006e0
    > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
    > Process swapper/0 (pid: 1, threadinfo ffff88003e272000, task ffff88003e278000)
    > Stack:
    > ffffffff810fed11 ffff88003dbd2680 ffff88003fd0d830 ffffffff81805980
    > ffff88003d48dd00 ffff88003fd0d860 ffffffff810aa687 ffff88003e2ad420
    > 0000000a3e2ad820 ffff88003e272000 ffff88003e278000 ffff88003fd03eb0
    > Call Trace:
    > <IRQ>
    > [<ffffffff810fed11>] ? kmem_cache_free+0x4f/0xd9
    > [<ffffffff810aa687>] ? __rcu_process_callbacks+0x1bf/0x2e2
    > [<ffffffff810aa7f4>] ? rcu_process_callbacks+0x4a/0x95
    > [<ffffffff8105cc1a>] ? __do_softirq+0xb6/0x171
    > [<ffffffff8155a58c>] ? call_softirq+0x1c/0x30
    > [<ffffffff81032d85>] ? do_softirq+0x31/0x68
    > [<ffffffff8105ce7f>] ? irq_exit+0x44/0x9e
    > [<ffffffff81047fd9>] ? smp_apic_timer_interrupt+0x85/0x95
    > [<ffffffff818d1000>] ? free_area_init_node+0x21f/0x2fb
    > [<ffffffff81559c4b>] ? apic_timer_interrupt+0x6b/0x70
    > <EOI>
    > [<ffffffff818d1000>] ? free_area_init_node+0x21f/0x2fb
    > [<ffffffff818d14b0>] ? __next_free_mem_range_rev+0x57/0x11e
    > [<ffffffff8104d31b>] ? free_init_pages+0xea/0x110
    > [<ffffffff810001c0>] ? init_post+0xe/0xbb
    > [<ffffffff81895b93>] ? kernel_init+0x10f/0x113
    > [<ffffffff8155a494>] ? kernel_thread_helper+0x4/0x10
    > [<ffffffff81895a84>] ? start_kernel+0x319/0x319
    > [<ffffffff8155a490>] ? gs_change+0xb/0xb
    > Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc <cc> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc
    > RIP [<ffffffff818b232b>] kmemleak_late_init+0x8a/0x8a
    > RSP <ffff88003fd03e58>
    > CR2: ffffffff818b232b

    I don't really see how kmemleak could cause such error (or any of the
    recent changes I have made). It looks like some of the code in the
    .init.text section is not executable.

    If you still have the vmlinux around, could you please run:

    addr2line -i -f -e vmlinux ffffffff818b232b

    The code shown shown in the oops message is also a bit weird (all 0xcc).
    Maybe you could do an objdump -d in that area, see if it looks like sane
    asm code.

    Thanks.

    --
    Catalin


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