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Message-ID: <20120402162716.4c93bfd3@pluto.restena.lu>
Date:	Mon, 2 Apr 2012 16:27:16 +0200
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	linux-kernel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [3.4-rc1 crash]: NULL pointer deref in
 fs/sysfs/group.c:create_files -- sysctl related?

Trying to boot a freshly built 3.4-rc1 (x86_64) kernel I'm getting the following
trace (server is HP Proliant G4):

[    0.986317] BUG: unable to handle kernel NULL pointer dereference at           (null)
[    0.990542] IP: [<ffffffff81152673>] internal_create_group+0x83/0x1a0
[    0.993693] PGD 0 
[    0.994682] Oops: 0000 [#1] SMP 
[    0.996198] CPU 0 
[    0.996198] Modules linked in:
[    0.996198] 
[    0.996198] Pid: 1, comm: swapper/0 Not tainted 3.4.0-rc1-x86_64 #3 HP ProLiant DL360 G4
[    0.996198] RIP: 0010:[<ffffffff81152673>]  [<ffffffff81152673>] internal_create_group+0x83/0x1a0
[    0.996198] RSP: 0018:ffff88019485fd70  EFLAGS: 00010202
[    0.996198] RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000001
[    0.996198] RDX: ffff880192e99908 RSI: ffff880192e99630 RDI: ffffffff81a26c60
[    0.996198] RBP: ffff88019485fdc0 R08: 0000000000000000 R09: 0000000000000000
[    0.996198] R10: ffff880192e99908 R11: 0000000000000000 R12: ffffffff81a16a00
[    0.996198] R13: ffff880192e99908 R14: ffffffff81a16900 R15: 0000000000000000
[    0.996198] FS:  0000000000000000(0000) GS:ffff88019bc00000(0000) knlGS:0000000000000000
[    0.996198] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[    0.996198] CR2: 0000000000000000 CR3: 0000000001a0c000 CR4: 00000000000007f0
[    0.996198] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    0.996198] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[    0.996198] Process swapper/0 (pid: 1, threadinfo ffff88019485e000, task ffff880194878000)
[    0.996198] Stack:
[    0.996198]  ffff88019485fdd0 ffff880192da9d60 0000000000000000 ffff880192e99908
[    0.996198]  ffff880192e995d8 0000000000000001 ffffffff81a16a00 ffff880192da9d60
[    0.996198]  0000000000000000 0000000000000000 ffff88019485fdd0 ffffffff811527be
[    0.996198] Call Trace:
[    0.996198]  [<ffffffff811527be>] sysfs_create_group+0xe/0x10
[    0.996198]  [<ffffffff81376ca6>] device_add_groups+0x46/0x80
[    0.996198]  [<ffffffff81377d3d>] device_add+0x46d/0x6a0
[    0.996198]  [<ffffffff81377891>] ? device_private_init+0x51/0x90
[    0.996198]  [<ffffffff81a98975>] ? utsname_sysctl_init+0x14/0x14
[    0.996198]  [<ffffffff810a7228>] pmu_dev_alloc+0x98/0xe0
[    0.996198]  [<ffffffff81a98975>] ? utsname_sysctl_init+0x14/0x14
[    0.996198]  [<ffffffff81a989c0>] perf_event_sysfs_init+0x4b/0x9a
[    0.996198]  [<ffffffff810002ad>] do_one_initcall+0x3d/0x170
[    0.996198]  [<ffffffff81a85cbd>] kernel_init+0x12d/0x1be
[    0.996198]  [<ffffffff81a85505>] ? rdinit_setup+0x28/0x28
[    0.996198]  [<ffffffff815f3714>] kernel_thread_helper+0x4/0x10
[    0.996198]  [<ffffffff81a85b90>] ? start_kernel+0x373/0x373
[    0.996198]  [<ffffffff815f3710>] ? gs_change+0xb/0xb
[    0.996198] Code: ff 85 c0 0f 85 bc 00 00 00 4c 8b 6d c8 4d 85 ed 74 15 41 8b 45 00 85 c0 0f 84 0b 01 00 00 f0 41 ff 45 00 4c 8b 6d c8 49 8b 5e 10 <48> 8b 03 48 85 c0 74 71 45 31 e4 eb 44 49 8b 46 08 48 85 c0 74 
[    0.996198] RIP  [<ffffffff81152673>] internal_create_group+0x83/0x1a0
[    0.996198]  RSP <ffff88019485fd70>
[    0.996198] CR2: 0000000000000000
[    1.131357] ---[ end trace 319c95c486d7d9cd ]---
[    1.133676] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009
[    1.133677] 


Short objdump analysis gives me:
ffffffff811525f0 <internal_create_group>:
ffffffff811525f0:       55                      push   %rbp
ffffffff811525f1:       48 89 e5                mov    %rsp,%rbp
ffffffff811525f4:       41 57                   push   %r15
ffffffff811525f6:       41 89 f7                mov    %esi,%r15d
ffffffff811525f9:       41 56                   push   %r14
ffffffff811525fb:       49 89 d6                mov    %rdx,%r14
ffffffff811525fe:       41 55                   push   %r13
ffffffff81152600:       41 54                   push   %r12
ffffffff81152602:       53                      push   %rbx
ffffffff81152603:       48 83 ec 28             sub    $0x28,%rsp
ffffffff81152607:       48 89 7d b8             mov    %rdi,-0x48(%rbp)
ffffffff8115260b:       48 85 ff                test   %rdi,%rdi
ffffffff8115260e:       0f 84 5b 01 00 00       je     ffffffff8115276f <internal_create_group+0x17f>
ffffffff81152614:       85 f6                   test   %esi,%esi
ffffffff81152616:       0f 84 48 01 00 00       je     ffffffff81152764 <internal_create_group+0x174>
ffffffff8115261c:       48 8b 55 b8             mov    -0x48(%rbp),%rdx
ffffffff81152620:       b8 ea ff ff ff          mov    $0xffffffea,%eax
ffffffff81152625:       48 83 7a 30 00          cmpq   $0x0,0x30(%rdx)
ffffffff8115262a:       0f 84 dd 00 00 00       je     ffffffff8115270d <internal_create_group+0x11d>
ffffffff81152630:       49 8b 36                mov    (%r14),%rsi
ffffffff81152633:       48 85 f6                test   %rsi,%rsi
ffffffff81152636:       0f 84 e4 00 00 00       je     ffffffff81152720 <internal_create_group+0x130>
ffffffff8115263c:       48 8d 55 c8             lea    -0x38(%rbp),%rdx
ffffffff81152640:       48 8b 7d b8             mov    -0x48(%rbp),%rdi
ffffffff81152644:       e8 37 e9 ff ff          callq  ffffffff81150f80 <sysfs_create_subdir>
ffffffff81152649:       85 c0                   test   %eax,%eax
ffffffff8115264b:       0f 85 bc 00 00 00       jne    ffffffff8115270d <internal_create_group+0x11d>
ffffffff81152651:       4c 8b 6d c8             mov    -0x38(%rbp),%r13
ffffffff81152655:       4d 85 ed                test   %r13,%r13
ffffffff81152658:       74 15                   je     ffffffff8115266f <internal_create_group+0x7f>
ffffffff8115265a:       41 8b 45 00             mov    0x0(%r13),%eax
ffffffff8115265e:       85 c0                   test   %eax,%eax
ffffffff81152660:       0f 84 0b 01 00 00       je     ffffffff81152771 <internal_create_group+0x181>
ffffffff81152666:       f0 41 ff 45 00          lock incl 0x0(%r13)
ffffffff8115266b:       4c 8b 6d c8             mov    -0x38(%rbp),%r13
ffffffff8115266f:       49 8b 5e 10             mov    0x10(%r14),%rbx
ffffffff81152673:       48 8b 03                mov    (%rbx),%rax
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ffffffff81152676:       48 85 c0                test   %rax,%rax
ffffffff81152679:       74 71                   je     ffffffff811526ec <internal_create_group+0xfc>
ffffffff8115267b:       45 31 e4                xor    %r12d,%r12d
ffffffff8115267e:       eb 44                   jmp    ffffffff811526c4 <internal_create_group+0xd4>
ffffffff81152680:       49 8b 46 08             mov    0x8(%r14),%rax
ffffffff81152684:       48 85 c0                test   %rax,%rax
ffffffff81152687:       74 56                   je     ffffffff811526df <internal_create_group+0xef>
ffffffff81152689:       44 89 e2                mov    %r12d,%edx

which matches (by comparing objdump with gcc -S fs/sysfs/group.c output):
static int create_files(struct sysfs_dirent *dir_sd, struct kobject *kobj,
            const struct attribute_group *grp, int update)
{
    struct attribute *const* attr;
    int error = 0, i;

    for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++) {
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        umode_t mode = 0;

        /* in update mode, we're changing the permissions or
         * visibility.  Do this by first removing then
         * re-adding (if required) the file */
        if (update)
            sysfs_hash_and_remove(dir_sd, NULL, (*attr)->name);
        if (grp->is_visible) {
            mode = grp->is_visible(kobj, *attr, i);
            if (!mode)
                continue;
        }
        error = sysfs_add_file_mode(dir_sd, *attr, SYSFS_KOBJ_ATTR,
                        (*attr)->mode | mode);
        if (unlikely(error))
            break;
    }
    if (error)
        remove_files(dir_sd, kobj, grp);
    return error;
}


I've not verified for sure, but from my understanding it must be grp->attrs that is NULL
and causes *attr test to explode.

Any immediate idea what it could be? (config attached)

Thanks,
Bruno
View attachment "3.4-rc1.config" of type "text/plain" (18358 bytes)

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