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    SubjectRe: [BUGFIX] NULL pointer dereference in __vm_enough_memory()
    [Balbir Singh - Sat, Aug 11, 2007 at 11:31:09PM +0530]
    | Andrew Morton wrote:
    | > On Sat, 11 Aug 2007 20:00:12 +0530 "Balbir Singh" <balbir@linux.vnet.ibm.com> wrote:
    | >
    | >> On 8/11/07, Fengguang Wu <fengguang.wu@gmail.com> wrote:
    | >
    | > hm, both people who replied to this removed Fengguang from cc. Disagreement
    | > between headers and MUAs, perhaps?
    | >
    |
    | Oops... Not sure how that happened. I'll check my sent mail.
    |
    | >>> Andrew,
    | >>>
    | >>> I'm not sure if this patch is the right fix for the bug. But it do
    | >>> stops the oops message. The bug also happens in 2.6.23-rc1-mm2/2.6.23-rc2-mm2.
    | >>> I'm running debian/sid. The .config is attached.
    | >>>
    | >>>
    | >>> Unable to handle kernel NULL pointer dereference at 0000000000000138 RIP
    | >>> [<ffffffff81092f66>] __vm_enough_memory+0x76/0x120
    | >>> PGD 7cd84067 PUD 7d9c3067 PMD 0
    | >>> Oops: 0000 [2] SMP
    | >>> CPU 1
    | >>> Modules linked in: eeprom lm85 hwmon_vid i2c_core tun fuse kvm snd_hda_intel snd_pcm_oss snd_mixer_oss snd_pcm snd_timer sg snd soundcore sr_mod cdrom snd_page_alloc pcspkr evdev button raid0 usbhid sd_mod uhci_hcd ehci_hcd ata_piix ahci ohci1394 ieee1394 thermal processor fan
    | >>> Pid: 4305, comm: khelper Tainted: G D 2.6.23-rc2 #9
    | >>> RIP: 0010:[<ffffffff81092f66>] [<ffffffff81092f66>] __vm_enough_memory+0x76/0x120
    | >>> RSP: 0000:ffff81007a3d1d30 EFLAGS: 00010206
    | >>> RAX: 0000000000000000 RBX: 0000000000000001 RCX: 000000000003e142
    | >>> RDX: 00000000000004f4 RSI: 0000000000000001 RDI: 0000000000000001
    | >>> RBP: ffff81007a3d1d40 R08: ffff81007a3d1d78 R09: 0000000000000000
    | >>> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
    | >>> R13: 0000000000000000 R14: ffff81007d0c0188 R15: ffff81007d577b18
    | >>> FS: 0000000000000000(0000) GS:ffff81007efa11d0(0000) knlGS:0000000000000000
    | >>> CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b
    | >>> CR2: 0000000000000138 CR3: 000000003799b000 CR4: 00000000000006e0
    | >>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    | >>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
    | >>> Process khelper (pid: 4305, threadinfo ffff81007a3d0000, task ffff81007a30acc0)
    | >>> Stack: 0000000000000001 ffff81007d577b18 ffff81007a3d1d60 ffffffff811297ff
    | >>> 0000000000000001 ffff810037c84bb8 ffff81007a3d1da0 ffffffff81092532
    | >>> ffff81007d0c0188 0000000000000000 ffff81007d577b20 0000000000000000
    | >>> Call Trace:
    | >>> [<ffffffff811297ff>] cap_vm_enough_memory+0x2f/0x40
    | >>> [<ffffffff81092532>] insert_vm_struct+0xa2/0xb0
    | >>> [<ffffffff810b020e>] bprm_mm_init+0x11e/0x1b0
    | >>> [<ffffffff810b1b71>] do_execve+0x81/0x220
    | >>> [<ffffffff8104bf90>] __call_usermodehelper+0x0/0x90
    | >>> [<ffffffff8100abc6>] sys_execve+0x46/0xb0
    | >>> [<ffffffff8104bf90>] __call_usermodehelper+0x0/0x90
    | >>> [<ffffffff8100cf64>] kernel_execve+0x64/0xd0
    | >>> [<ffffffff8104bf90>] __call_usermodehelper+0x0/0x90
    | >>> [<ffffffff8104c384>] ____call_usermodehelper+0x174/0x190
    | >>> [<ffffffff8100cef8>] child_rip+0xa/0x12
    | >>> [<ffffffff810356f8>] schedule_tail+0x78/0x100
    | >>> [<ffffffff8100c60c>] restore_args+0x0/0x30
    | >>> [<ffffffff8104c210>] ____call_usermodehelper+0x0/0x190
    | >>> [<ffffffff8100ceee>] child_rip+0x0/0x12
    | >>>
    | >>>
    | >>> Code: 48 8b 80 38 01 00 00 48 c1 e8 05 48 29 c1 48 39 ca 0f 8c 89
    | >>> RIP [<ffffffff81092f66>] __vm_enough_memory+0x76/0x120
    | >>> RSP <ffff81007a3d1d30>
    | >>> CR2: 0000000000000138
    | >>>
    | >>> Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
    | >>> ---
    | >>> mm/mmap.c | 3 ++-
    | >>> 1 file changed, 2 insertions(+), 1 deletion(-)
    | >>>
    | >>> --- linux-2.6.23-rc2-mm2.orig/mm/mmap.c
    | >>> +++ linux-2.6.23-rc2-mm2/mm/mmap.c
    | >>> @@ -166,7 +166,8 @@ int __vm_enough_memory(long pages, int c
    | >>>
    | >>> /* Don't let a single process grow too big:
    | >>> leave 3% of the size of this process for other processes */
    | >>> - allowed -= current->mm->total_vm / 32;
    | >>> + if (current->mm)
    | >>> + allowed -= current->mm->total_vm / 32;
    | >>>
    | >>> /*
    | >>> * cast `allowed' as a signed long because vm_committed_space
    | >>>
    | >>>
    | >> Shouldn't we just not stop vm accounting for kernel threads?
    | >>
    | >
    | > Could be. It'd help heaps if we knew which patch in -mm caused
    | > this, but from a quick peek it seems to me that mainline should be
    | > vulnerable as well.
    |
    | Thats a valid point. It would be interesting to see what the overcommit
    | setting was, when the panic occurred.

    May I suggest - could it be commit b6a2fea39318e43fee84fa7b0b90d68bed92d2ba
    Not sure but take a look please

    Cyrill

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