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SubjectRe: [Linux-NTFS-Dev] Oops with corrupted NTFS image
On 07.07.2008 15:03, Vegard Nossum wrote:
> On Mon, Jul 7, 2008 at 2:24 PM, Eric Sesterhenn <snakebyte@gmx.de> wrote:
>
>> (gdb) l *(ntfs_read_locked_inode+0x16c)
>> 0xc030adbc is in ntfs_read_locked_inode (fs/ntfs/time.h:90).
>> 85 static inline struct timespec ntfs2utc(const sle64 time)
>> 86 {
>> 87 struct timespec ts;
>> 88
>> 89 /* Subtract the NTFS time offset. */
>> 90 u64 t = (u64)(sle64_to_cpu(time) - NTFS_TIME_OFFSET);
>> 91 /*
>> 92 * Convert the time to 1-second intervals and the remainder to
>> 93 * 1-nano-second intervals.
>> 94 */
>> (gdb) quit
>>
>> Not sure why this happens. I checked out a fresh git tree to
>> make sure my tree isnt broken or something. Might gcc be bogus
>> or the debug information and the bug happens in reality somewhere else?
>>

As I pointed out in my other mail, gcc compiler optimizations may have
caused a slightly off location being printed.
My suspicions about time were correct.

> Are you sure you didn't recompile/relink vmlinux after getting the
> error? If not, maybe it's gdb which gets confused (somehow) by the
> inlining.
>
> Your 'Code:' line decodes to these instructions:
>
> 0: 8b 58 08 mov 0x8(%eax),%ebx
> 3: 8b 70 0c mov 0xc(%eax),%esi
>
> And I find this in my own compiled vmlinux at:
>
> c025bcc1: 8b 58 08 mov 0x8(%eax),%ebx
> c025bcc4: 8b 70 0c mov 0xc(%eax),%esi
>
> which is at...
>
> $ addr2line -e vmlinux -i c025bcc1
> fs/ntfs/inode.c:670
>
> which is...
>
> vi->i_mtime = ntfs2utc(si->last_data_change_time);
>
> which is probably what is causing the NULL pointer dereference.
>

The problem of this theory is that there is no NULL pointer dereference,
unless you meant "invalid memory access".

Regards,
Carl-Daniel

--
http://www.hailfinger.org/



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