On Fri, Jun 18, 2010 at 1:19 PM, Manish Katiyar <mkatiyar@xxxxxxxxx> wrote:
Thanks Manish for your reply. The problem was with the return value in FS create() call. The create() call was returning the +ve error code. I looked into some of the other file systems, they use PTR_ERR to return the error code. Basically the -ve error code is assigned to unsigned long causing, thus converting it in a big number.
struct file *f = do_filp_open(dfd, tmp, flags, mode, 0);
if (IS_ERR(f)) {
put_unused_fd(fd);
fd = PTR_ERR(f);
} else {
fsnotify_open(f->f_path.dentry); <=== OOPs
fd_install(fd, f);
}
So IS_ERR() was returning false and causing panic in else path.
Thanks a lot for your help.
Regards,
Prasad
On Fri, Jun 18, 2010 at 10:11 AM, Prasad Joshi <prasadjoshi124@xxxxxxxxx> wrote:
As ppl have already mentioned, this is some offset into a structure.> Hi All,
>
> I am trying to understand a a kernel oops report. Here are some of the
> fields from the report
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000034
> Oops: 0000 [#1] SMP
> Pid: 6478, comm: cp Tainted: P 2.6.31.5-127.fc12.x86_64 #1 Inspiron 1525
> RIP: 0010:[<ffffffff810faac1>] [<ffffffff810faac1>] do_sys_open+0x7a/0x10f
> CR2: 0000000000000034
>
> As I know, when a page fault occurs, the address the program attempted to
> access is stored in the CR2 register. So probably the pointer is pointing to
> address 0034 and is being access.
>
> The BUG string is bit confusing, it says NULL pointer dereference at 0034, I
> know the address 00034 is not valid but why is it interpreted as NULL
> pointer? The NULL pointer as I know should point to address 0.
Next thing you can try is to do a disas do_sys_open and find out which
member/structure is being accessed which has this offset. You can also
try to get the assembly instructions from the "code" dumped. if you
already have the source code for your running kernel you can also try
"l *do_sys_open+0x7a".
Thanks Manish for your reply. The problem was with the return value in FS create() call. The create() call was returning the +ve error code. I looked into some of the other file systems, they use PTR_ERR to return the error code. Basically the -ve error code is assigned to unsigned long causing, thus converting it in a big number.
struct file *f = do_filp_open(dfd, tmp, flags, mode, 0);
if (IS_ERR(f)) {
put_unused_fd(fd);
fd = PTR_ERR(f);
} else {
fsnotify_open(f->f_path.dentry); <=== OOPs
fd_install(fd, f);
}
So IS_ERR() was returning false and causing panic in else path.
Thanks a lot for your help.
Regards,
Prasad
>
> Thanks and Regards,
> Prasad
>
--
Thanks -
Manish
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